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Sökning: WFRF:(Alfredsson Magnus)

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1.
  • Engström, Gunnar, et al. (författare)
  • Pulmonary function and atherosclerosis in the general population : causal associations and clinical implications
  • 2024
  • Ingår i: European Journal of Epidemiology. - : Springer Nature. - 0393-2990 .- 1573-7284. ; 39:1, s. 35-49
  • Tidskriftsartikel (refereegranskat)abstract
    • Reduced lung function is associated with cardiovascular mortality, but the relationships with atherosclerosis are unclear. The population-based Swedish CArdioPulmonary BioImage study measured lung function, emphysema, coronary CT angiography, coronary calcium, carotid plaques and ankle-brachial index in 29,593 men and women aged 50–64 years. The results were confirmed using 2-sample Mendelian randomization. Lower lung function and emphysema were associated with more atherosclerosis, but these relationships were attenuated after adjustment for cardiovascular risk factors. Lung function was not associated with coronary atherosclerosis in 14,524 never-smokers. No potentially causal effect of lung function on atherosclerosis, or vice versa, was found in the 2-sample Mendelian randomization analysis. Here we show that reduced lung function and atherosclerosis are correlated in the population, but probably not causally related. Assessing lung function in addition to conventional cardiovascular risk factors to gauge risk of subclinical atherosclerosis is probably not meaningful, but low lung function found by chance should alert for atherosclerosis.
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2.
  • Agrell, Erik, 1965, et al. (författare)
  • Modulation and detection for multicore superchannels with correlated phase noise [Invited]
  • 2018
  • Ingår i: 2018 Conference on Lasers and Electro-Optics, CLEO 2018 - Proceedings. ; Part F94-CLEO_SI 2018
  • Konferensbidrag (refereegranskat)abstract
    • SDM fibers offer new opportunities and challenges for joint transmitter and receiver processing. We review multidimensional modulation and detection theory, describe algorithms for phase tracking and detection over spatial superchannels, and present some experimental results.
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3.
  • Alfredsson, Arni, 1989, et al. (författare)
  • On the Impact of Intercore Skew on Joint-Core Carrier-Phase Estimation
  • 2019
  • Ingår i: European Conference on Optical Communication, ECOC. - : Institution of Engineering and Technology. ; 2019:CP765
  • Konferensbidrag (refereegranskat)abstract
    • The impact of intercore skew on joint-core carrier-phase estimation in multicore-fiber transmission is studied. It is shown that the performance degradation is not dependent on the combined linewidth of the light-source laser and the local oscillator, but rather the ratio between the two linewidths.
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4.
  • Alfredsson, Arni, 1989, et al. (författare)
  • On the Performance of Joint-Core Carrier-Phase Estimation in the Presence of Intercore Skew
  • 2019
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:20, s. 5291-5298
  • Tidskriftsartikel (refereegranskat)abstract
    • The sharing of lasers in space-division multiplexed multicore-fiber transmission yields correlated phase noise across the spatial channels. As a result, system performance can be improved through the use of joint-core carrier-phase estimation (CPE). However, the presence of intercore skew can reduce the potential of such schemes. This paper studies the effects of skew on pilot-aided joint-core CPE, where via simulations, it is shown that joint-core processing can be made to perform similarly to or better than separate-core processing for any amount of skew. It is shown that for a given signal-to-noise ratio (SNR) and skew, the performance of joint-core CPE relative to separate-core CPE is highly dependent on the ratio of the light-source linewidth to the local oscillator (LO) linewidth. In general, the performance of joint-core CPE in the presence of skew improves as the LO linewidth decreases compared to the light-source laser linewidth, assuming that the spatial channels are digitally realigned at the receiver.
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5.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Optimization of Transmitter-Side Signal Rotations in the Presence of Laser Phase Noise
  • 2020
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 38:15, s. 3850-3858
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of transmitter-side multidimensional signal rotations on the performance of multichannel optical transmission are studied in the presence of laser phase noise. In particular, the laser phase noise is assumed to be uncorrelated between channels. To carry out this study, a simple multichannel laser-phase-noise model that has been experimentally validated for weakly-coupled multicore-fiber transmission is considered. As the considered rotation scheme is intended to work in conjunction with receiver-side carrier phase estimation (CPE), the model is modified to further assume that imperfect CPE has taken place, leaving residual phase noise in the processed signal. Based on this model, two receiver structures are derived and used to numerically optimize transmitter-side signal rotations through Monte Carlo simulations. For reasonable amounts of residual phase noise, rotations based on Hadamard matrices are found to be near-optimal for transmission of four-dimensional signals. Furthermore, Hadamard rotations can be performed for any dimension that is a power of two. By exploiting this property, an increase of up to 0.25 bit per complex symbol in an achievable information rate is observed for transmission of higher-order constellations.
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6.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Phase-Noise Compensation for Spatial-Division Multiplexed Transmission
  • 2017
  • Ingår i: Optics InfoBase Conference Papers. - 2162-2701. ; Part F40-OFC 2017
  • Konferensbidrag (refereegranskat)abstract
    • The problem of correlated phase noise in spatial-division multiplexed transmission is studied. To compensate for the phase noise, an algorithm for joint-core phase-noise estimation and symbol detection is proposed, which outperforms conventional methods.
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7.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Pilot-Aided Joint-Channel Carrier-Phase Estimation in Space-Division Multiplexed Multicore Fiber Transmission
  • 2019
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:4, s. 1133-1142
  • Tidskriftsartikel (refereegranskat)abstract
    • The performance of pilot-aided joint-channel carrier-phase estimation (CPE) in space-division multiplexed multicore fiber (MCF) transmission with correlated phase noise is studied. To that end, a system model describing uncoded MCF transmission where the phase noise comprises a common laser phase noise, in addition to core- and polarization-specific phase drifts, is introduced. It is then shown that the system model can be regarded as a special case of a multidimensional random-walk phase-noise model. A pilot-aided CPE algorithm developed for this model is used to evaluate two strategies, namely joint-channel and per-channel CPE. To quantify the performance differences between the two strategies, their respective phase-noise tolerances are assessed through Monte Carlo simulations of uncoded transmission for different modulation formats, pilot overheads, laser linewidths, numbers of spatial channels, and degrees of phase-noise correlation across the channels. For 20 GBd transmission with 200 kHz combined laser linewidth and 1% pilot overhead, joint-channel CPE yields up to 3.4 dB improvement in power efficiency or 25.5% increased information rate. Moreover, through MCF transmission experiments, the system model is validated and the strategies are compared in terms of bit-error-rate performance versus transmission distance for uncoded transmission of different modulation formats. Up to 21% increase in transmission reach is observed for 1% pilot overhead through the use of joint-channel CPE.
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8.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Pilot Distributions for Joint-Channel Carrier-Phase Estimation in Multichannel Optical Communications
  • 2020
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 38:17, s. 4656-4663
  • Tidskriftsartikel (refereegranskat)abstract
    • Joint-channel carrier-phase estimation can improve the performance of multichannel optical communication systems. In the case of pilot-aided estimation, the pilots are distributed over a two-dimensional channel-time symbol block that is transmitted through multiple channels. However, suboptimal pilot distributions reduce the effectiveness of the carrier-phase estimation and thus result in unnecessary pilot overhead, which reduces the overall information rate of the system. It is shown that placing pilots identically in all channels is suboptimal in general. By instead optimizing the pilot distribution, the mean squared error of the phase-noise estimates can be decreased by over 90% in some cases. Moreover, it is shown that the achievable information rate can be increased by up to 0.05, 0.16, and 0.41 bits per complex symbol for dual-polarization 20 GBd transmission of 64-ary, 256-ary, and 1024-ary quadrature amplitude modulation over 20 four-dimensional channels, respectively, assuming a total laser linewidth of 200 kHz.
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9.
  • Alfredsson, Arni, 1989, et al. (författare)
  • Pilot Distributions for Phase Tracking in Space-Division Multiplexed Systems
  • 2017
  • Ingår i: European Conference on Optical Communication, ECOC. ; 2017-September
  • Konferensbidrag (refereegranskat)abstract
    • Several pilot distributions are compared for pilot-aided joint-core phase tracking in space-division multiplexed transmission affected by correlated phase noise. Results show that the best choice of distribution can reduce the bit error rate by a factor up to 170.
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10.
  • Alfredsson, Eva, 1963-, et al. (författare)
  • Why achieving the Paris Agreement requires reduced overall consumption and production
  • 2018
  • Ingår i: Sustainability. - : Informa UK Limited. - 1548-7733. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • Technological solutions to the challenge of dangerous climate change are urgent and necessary but to be effective they need to be accompanied by reductions in the total level of consumption and production of goods and services. This is for three reasons. First, private consumption and its associated production are among the key drivers of greenhouse-gas (GHG) emissions, especially among highly emitting industrialized economies. There is no evidence that decoupling of the economy from GHG emissions is possible at the scale and speed needed. Second, investments in more sustainable infrastructure, including renewable energy, needed in coming decades will require extensive amounts of energy, largely from fossil sources, which will use up a significant share of the two-degree carbon budget. Third, improving the standard of living of the world’s poor will consume a major portion of the available carbon allowance. The scholarly community has a responsibility to put the issue of consumption and the associated production on the research and policy agenda.
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11.
  • Alfredsson, Joakim, 1962-, et al. (författare)
  • Bleeding complications with clopidogrel or ticagrelor in ST-elevation myocardial infarction patients : A real life cohort study of two treatment strategies
  • 2020
  • Ingår i: IJC Heart & Vasculature. - : Elsevier. - 2352-9067. ; 27
  • Tidskriftsartikel (refereegranskat)abstract
    • IntroductionDual antiplatelet therapy (DAPT), including potent P2Y12 inhibition after ST-elevation myocardial infarction (STEMI) is recommended in clinical guidelines. However, bleeding complications are common, and associated with worse outcomes. The aim of this study was to assess incidence of bleeding events with a clopidogrel-based compared to a ticagrelor-based DAPT strategy, in a real world population. Secondary aims were to assess ischemic complications and mortality.Methods and ResultsWe identified 330 consecutive STEMI patients with a clopidogrel-based and 330 with a ticagrelor-based DAPT strategy. Patientś medical records were searched for bleeding and ischemic complications, over 6 months follow-up.The two groups were well balanced in baseline characteristics, age (69 years inboth groups), sex (31% vs 32% females), history of diabetes (19% vs 21%), hypertension (43% in both) and MI (17% vs 15%). There was no difference in CRUSADE bleeding score (28 vs 29). After discharge, there were more than twice as many bleeding events with a ticagrelor-based compared with a clopidogrel-based strategy (13.3% vs. 6.5%, p = 0.005). Bleeding events included significantly more severe bleeding complications (TIMI major/minor [5.8 vs 1.0, p = 0.001]) during the ticagrelor-based period. There was no significant difference in the composite of death, MI or stroke (7.8% vs 7.1%, p = 0.76).ConclusionsIn this observational study, a ticagrelor-based DAPT strategy was associated with significantly more bleeding complications, without any significant change in death, MI or stroke. Larger studies are needed to determine whether bleeding complications off-sets benefits with a more potent DAPT strategy in older and more comorbid real-life patients.
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12.
  • Alfredsson, Joakim, et al. (författare)
  • Individual long-term variation of platelet reactivity in patients with dual antiplatelet therapy after myocardial infarction.
  • 2019
  • Ingår i: Platelets. - : Informa UK Limited. - 0953-7104 .- 1369-1635. ; 30:5, s. 572-578
  • Tidskriftsartikel (refereegranskat)abstract
    • There is a large inter-individual variation in response to clopidogrel treatment, and previous studies have indicated higher risk of thrombotic events in those with high residual platelet reactivity (HPR). Less is known about individual variation over time. The aim of this prospective cohort study was to investigate intra-individual variation in platelet reactivity. Platelet aggregation in whole blood was assessed in 77 patients, at 3 days, 8 days and 6 months after admission for acute myocardial infarction and loading dose of clopidogrel. All patients were treated with aspirin and clopidogrel through 6-month follow-up. We found a significant increase in median ADP-stimulated aggregation from third to eighth day (195 vs. 250 AU*min, p-value = 0.001) but not from day 8 to 6 months (250 vs. 223 AU*min, p-value = 0.666). There was no significant change in the overall rate of HPR (15.6% vs 20.8%, p-value 0.503) or low platelet reactivity (LPR) (37.7% vs 33.8%, p-value = 0.609) from day 8 to 6-month follow-up. In contrast, more than one in four changed HPR status, 15.6% from non-HPR to HPR and 10.4% HPR to non-HPR. A shift in LPR status appeared even more frequent, occurring in about one of three patients. In spite of similar median aggregation and rate of HPR during 6-month follow-up, about one in four of the patients changed HPR status and one in three changed LPR status. This may be important information for a concept of risk stratification based on a single aggregation value early after an acute coronary syndromes.
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13.
  • Alfredsson, Joakim, et al. (författare)
  • Large early variation of residual platelet reactivity in Acute Coronary Syndrome patients treated with clopidogrel : Results from Assessing Platelet Activity in Coronary Heart Disease (APACHE).
  • 2015
  • Ingår i: Thrombosis Research. - : Pergamon Press. - 0049-3848 .- 1879-2472. ; 136:2, s. 335-340
  • Tidskriftsartikel (refereegranskat)abstract
    • INTRODUCTION: There is a large inter-individual variation in response to clopidogrel treatment and previous studies have indicated higher risk of thrombotic events in patients with high residual platelet reactivity (HRPR), but the optimal time-point for testing is not established. The aim of this study was to investigate the optimal time-point for aggregometry testing and the risk of major adverse cardiac events associated with HRPR.METHOD AND RESULTS: We included 125 patients with ACS (73 with STEMI, and 71 received abciximab). The prevalence of HRPR varied substantially over time. The rate of HRPR in patients treated and not treated with abciximab were 43% vs 67% (p=0.01) before, 2% vs 23% (p=0.001) 6-8h after, 8% vs 9% (p=0.749) 3days after, and 23% vs 12% (p=0.138) 7-9 days after loading dose of clopidogrel. We found HRPR in 18% of the patients but only four ischemic events during 6months follow-up, with no significant difference between HRPR patients compared to the rest of the population. There were 3 TIMI major bleedings, all of which occurred in the low residual platelet reactivity (LRPR) group.CONCLUSION: There is a large variation in platelet reactivity over time, also depending on adjunctive therapy, which has a large impact on optimal time-point for assessment. We found HRPR in almost 1 in 5 patients, but very few MACE, and not significantly higher in HRPR patients. In a contemporary ACS population, with low risk for stent thrombosis, the predictive value of HRPR for ischemic events will probably be low.
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14.
  • Alfredsson, Joakim, et al. (författare)
  • Predicting the risk of bleeding during dual antiplatelet therapy after acute coronary syndromes
  • 2017
  • Ingår i: Heart. - : BMJ PUBLISHING GROUP. - 1355-6037 .- 1468-201X. ; 103:15, s. 1168-1176
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives Dual antiplatelet therapy (DAPT) with aspirin + a P2Y12 inhibitor is recommended for at least 12 months for patients with acute coronary syndrome (ACS), with shorter durations considered for patients with increased bleeding risk. However, there are no decision support tools available to predict an individual patients bleeding risk during DAPT treatment in the post-ACS setting. Methods To develop a longitudinal bleeding risk prediction model, we analysed 9240 patients with unstable angina/non-ST segment elevation myocardial infarction (NSTEMI) from the Targeted Platelet Inhibition to Clarify the Optimal Strategy to Medically Manage Acute Coronary Syndromes (TRILOGY ACS) trial, who were managed without revascularisation and treated with DAPT for a median of 14.8 months. Results We identified 10 significant baseline predictors of non-coronary artery bypass grafting (CABG)-related Global Use of Strategies to Open Occluded Arteries (GUSTO) severe/life-threatening/moderate bleeding: age, sex, weight, NSTEMI (vs unstable angina), angiography performed before randomisation, prior peptic ulcer disease, creatinine, systolic blood pressure, haemoglobin and treatment with beta-blocker. The five significant baseline predictors of Thrombolysis In Myocardial Infarction (TIMI) major or minor bleeding included age, sex, angiography performed before randomisation, creatinine and haemoglobin. The models showed good predictive accuracy with Therneaus C-indices: 0.78 (SE=0.024) for the GUSTO model and 0.67 (SE=0.023) for the TIMI model. Internal validation with bootstrapping gave similar C-indices of 0.77 and 0.65, respectively. External validation demonstrated an attenuated C-index for the GUSTO model (0.69) but not the TIMI model (0.68). Conclusions Longitudinal bleeding risks during treatment with DAPT in patients with ACS can be reliably predicted using selected baseline characteristics. The TRILOGY ACS bleeding models can inform riskbenefit considerations regarding the duration of DAPT following ACS.
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15.
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16.
  • Alfredsson, Magnus, et al. (författare)
  • Funktionskriterier för vägkonstruktioner : Förstudie
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Det projekt som här rapporteras har som syfte att identifiera och beskriva de svårigheter och möjligheter som totalentreprenader medför, respektive erbjuder, för alla parter. Målet är att utveckla totalentreprenader på ett sådant sätt att branschens effektivitet ökas. Denna rapport är en förstudie där det studerats vilka krav som byggherren ska ställa på utföraren av en vägkonstruktion i en totalentreprenad med funktionsansvar och hur utföraren ska verifiera kraven. Arbetet har genomförts med medlemmar från olika aktörer i branschen och omfattat främst litteraturstudier och intervjuer. Kunskaper och erfarenheter har sammanställts och analyserats för att slutligen kondenseras ned till ett antal förslag till fortsatt arbete.Förstudien har pekat ut ett antal områden som viktiga för att påskynda framtida utveckling av totalentreprenader:Terminologi – idag råder viss begreppsförvirringAnalys av funktionella krav i tidigare projektTrafikantkravMiljökravUtveckling av funktionella krav i samverkanVäghållarekonomiRegelbetingade begränsningar av funktionella kravUppföljning och underlättande av erfarenhetsackumuleringImplementering av nya mått och mätmetoder
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17.
  • Alfredsson, R., et al. (författare)
  • Why do parents hesitate to vaccinate their children against measles, mumps and rubella?
  • 2004
  • Ingår i: Acta Paediatr. - 0803-5253. ; 93:9, s. 1232-7
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Thanks to a successful voluntary vaccination programme, measles, mumps and rubella are rare diseases in Sweden. Coverage among children 18 mo of age has been 99%, but the measles, mumps and rubella vaccination (MMR) has increasingly been questioned among parents. AIM: To study reasons why parents choose not to vaccinate their child against measles, mumps and rubella, and their opinions on vaccines and the diseases themselves. A secondary objective was to compare coverage at 18 mo of age based on parental report with the national statistics based on patient charts. METHODS: The official statistics were compared with patient charts for two birth cohorts in the city of Goteborg, Sweden. Out of these children born in 1995 and 1996, 300 unvaccinated and vaccinated children were identified. Their parents received a postal questionnaire assessing the parent's views on vaccines and childhood diseases. RESULTS: The documented vaccine coverage in this study was higher in 1995 and 1996 than official statistics indicated. The major reason, for both groups, for accepting respectively declining vaccination was strengthening the child's immune system. Parents with children unvaccinated against MMR were also more likely to have declined vaccination against diphtheria, polio, tetanus, Haemophilus influenzae and pertussis. One-third of the parents with a child unvaccinated against MMR had not yet made their final decision 3 y after the vaccine offer. Few parents, both with vaccinated and unvaccinated children, had acquired vaccine information from the Internet. Both groups believed that insufficient time was allocated for vaccine information and discussion at the Child Health Centre. CONCLUSION: Our study indicates that official statistics on MMR vaccination uptake underestimate the number of vaccinated children. Vaccine safety is a major concern for many parents and needs to be addressed by healthcare professionals at institutions offering paediatric vaccinations.
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18.
  • Bengtsson, Magnus, et al. (författare)
  • Transforming systems of consumption and production for achieving the sustainable development goals : moving beyond efficiency
  • 2018
  • Ingår i: Sustainability Science. - : SPRINGER JAPAN KK. - 1862-4065 .- 1862-4057. ; 13:6, s. 1533-1547
  • Tidskriftsartikel (refereegranskat)abstract
    • The United Nations formulated the sustainable development goals (SDGs) in 2015 as a comprehensive global policy framework for addressing the most pressing social and environmental challenges currently facing humanity. In this paper, we analyse SDG 12, which aims to ensure sustainable consumption and production patterns. Despite long-standing political recognition of this objective, and ample scientific evidence both on its importance and on the efficacy of various ways of promoting it, the SDGs do not provide clear goals or effective guidance on how to accomplish this urgently needed transformation. Drawing from the growing body of research on sustainable consumption and production (SCP), the paper identifies two dominant vantage pointsone focused on promoting more efficient production methods and products (mainly through technological improvement and informed consumer choice) and the other stressing the need to consider also overall volumes of consumption, distributional issues, and related social and institutional changes. We label these two approaches efficiency and systemic. Research shows that while the efficiency approach contains essential elements of a transition to sustainability, it is by itself highly unlikely to bring about sustainable outcomes. Concomitantly, research also finds that volumes of consumption and production are closely associated with environmental impacts, indicating a need to curtail these volumes in ways that safeguard social sustainability, which is unlikely to be possible without a restructuring of existing socioeconomic arrangements. Analysing how these two perspectives are reflected in the SDGs framework, we find that in its current conception, it mainly relies on the efficiency approach. On the basis of this assessment, we conclude that the SDGs represent a partial and inadequate conceptualisation of SCP which will hamper implementation. Based on this determination, this paper provides some suggestions on how governments and other actors involved in SDGs operationalisation could more effectively pursue SCP from a systemic standpoint and use the transformation of systems of consumption and production as a lever for achieving multiple sustainability objectives.
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19.
  • Bergström, Göran, 1964, et al. (författare)
  • Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population
  • 2021
  • Ingår i: Circulation. - Philadelphia : American Heart Association. - 0009-7322 .- 1524-4539. ; 144:12, s. 916-929
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population.Methods: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data.Results: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population.Conclusions: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.
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20.
  • Bergström, Göran, et al. (författare)
  • Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population
  • 2021
  • Ingår i: Circulation. - : Wolters Kluwer. - 0009-7322 .- 1524-4539. ; 144:12, s. 916-929
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population.Methods: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data.Results: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population.Conclusions: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.
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21.
  • De Geer, Jakob, et al. (författare)
  • Software-based on-site estimation of fractional flow reserve using standard coronary CT angiography data.
  • 2016
  • Ingår i: Acta Radiologica. - : Sage Publications. - 0284-1851 .- 1600-0455. ; 57:10, s. 1186-1192
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: The significance of a coronary stenosis can be determined by measuring the fractional flow reserve (FFR) during invasive coronary angiography. Recently, methods have been developed which claim to be able to estimate FFR using image data from standard coronary computed tomography angiography (CCTA) exams.PURPOSE: To evaluate the accuracy of non-invasively computed fractional flow reserve (cFFR) from CCTA.MATERIAL AND METHODS: A total of 23 vessels in 21 patients who had undergone both CCTA and invasive angiography with FFR measurement were evaluated using a cFFR software prototype. The cFFR results were compared to the invasively obtained FFR values. Correlation was calculated using Spearman's rank correlation, and agreement using intraclass correlation coefficient (ICC). Sensitivity, specificity, accuracy, negative predictive value, and positive predictive value for significant stenosis (defined as both FFR ≤0.80 and FFR ≤0.75) were calculated.RESULTS: The mean cFFR value for the whole group was 0.81 and the corresponding mean invFFR value was 0.84. The cFFR sensitivity for significant stenosis (FFR ≤0.80/0.75) on a per-lesion basis was 0.83/0.80, specificity was 0.76/0.89, and accuracy 0.78/0.87. The positive predictive value was 0.56/0.67 and the negative predictive value was 0.93/0.94. The Spearman rank correlation coefficient was ρ = 0.77 (P < 0.001) and ICC = 0.73 (P < 0.001).CONCLUSION: This particular CCTA-based cFFR software prototype allows for a rapid, non-invasive on-site evaluation of cFFR. The results are encouraging and cFFR may in the future be of help in the triage to invasive coronary angiography.
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22.
  • Ekerstad, Niklas, et al. (författare)
  • Clinical frailty scale – skörhet är ett sätt att skatta biologisk ålder
  • 2022
  • Ingår i: Lakartidningen. - 0023-7205. ; 119, s. 1-5
  • Forskningsöversikt (refereegranskat)abstract
    • The term frailty denotes a multi-dimensional syndrome characterised by reduced physiological reserves and increased vulnerability. Frailty may be used as a marker of biological age, distinct from chronological age. There are several instruments for frailty assessment. The Clinical Frailty Scale (CFS) is probably the most commonly used in the acute care context. It is a 9-level scale, derived from the accumulated deficit model of frailty, which combines comorbidity, disability, and cognitive impairment. The CFS assessment is fast and easy to implement in daily clinical practice. The CFS is relevant for risk stratification, and may also be used as a screening instrument to identify frail patients suitable for further geriatric evaluation, i.e. a comprehensive geriatric assessment (CGA). By providing information on long-term prognosis, it may improve informed decision-making on an individual basis.
  •  
23.
  • Ekerstad, Niklas, 1969-, et al. (författare)
  • Clinical frailty scale – skörhet ärett sätt att skatta biologisk ålder : [Clinical Frailty Scale - a proxy estimate of biological age]
  • 2022
  • Ingår i: Läkartidningen. - : Sveriges Läkarforbund. - 0023-7205 .- 1652-7518. ; 119
  • Forskningsöversikt (refereegranskat)abstract
    • The term frailty denotes a multi-dimensional syndrome characterised by reduced physiological reserves and increased vulnerability. Frailty may be used as a marker of biological age, distinct from chronological age. There are several instruments for frailty assessment. The Clinical Frailty Scale (CFS) is probably the most commonly used in the acute care context. It is a 9-level scale, derived from the accumulated deficit model of frailty, which combines comorbidity, disability, and cognitive impairment. The CFS assessment is fast and easy to implement in daily clinical practice. The CFS is relevant for risk stratification, and may also be used as a screening instrument to identify frail patients suitable for further geriatric evaluation, i.e. a comprehensive geriatric assessment (CGA). By providing information on long-term prognosis, it may improve informed decision-making on an individual basis.
  •  
24.
  • Ekerstad, Niklas, 1969-, et al. (författare)
  • Frailty as a Predictor of Short-Term Outcomes for Elderly Patients with non-ST-Elevation Myocardial Infarction (NSTEMI)
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Background – For the large and growing population of elderly patients with cardiovascular disease it is important to identify clinically relevant measures of biological age and their contribution to risk. Frailty is an emerging concept in medicine denoting increased vulnerability and decreased physiologic reserves. We analyzed how the variable frailty predicts short-term outcomes for elderly NSTEMI patients. Methods and Results – Patients, aged 75 years or older, with diagnosed NSTEMI were included at three centers, and clinical data including judgement of frailty were collected prospectively. Frailty was defined according to the Canadian Study of Health and Aging (CSHA) Clinical Frailty Scale (CFS). Of 307 patients, 150 (48.5%) were considered frail. Frail patients were slightly older and presented with a greater burden of comorbidity. By multiple logistic regression, frailty was found to be a strong independent risk factor for inhospital mortality, one-month mortality (OR 3.8, 95% CI 1.3 to 10.8) and the primary composite outcome (OR 2.2, 95% CI 1.3 to 3.7). Particularly frail patients with a high comorbidity burden manifested a markedly increased risk for the primary composite outcome. By multiple linear regression, frailty was identified as a strong independent predictor for prolonged hospital care (frail 13.4 bed days, non-frail 7.5 bed days; P<0.0001). Conclusions - Frailty is a strong independent predictor of in-hospital mortality, one-month mortality, prolonged hospital care and the primary composite outcome. The combined use of frailty and comorbidity may constitute an ultimate risk prediction concept regarding cardiovascular patients with complex needs.
  •  
25.
  • Ekerstad, Niklas, et al. (författare)
  • Frailty as an instrument for evaluation of elderly patients with non-ST-segment elevation myocardial infarction: A follow-up after more than 5 years
  • 2018
  • Ingår i: European Journal of Preventive Cardiology. - : SAGE PUBLICATIONS LTD. - 2047-4873 .- 2047-4881. ; 25:17, s. 1813-1821
  • Tidskriftsartikel (refereegranskat)abstract
    • Background There is a growing body of evidence on the relevance of using frailty measures also in a cardiovascular context. The estimated time to death is crucial in clinical decision-making in cardiology. However, data on the importance of frailty in long-term mortality are very scarce. The aim of the study was to assess the prognostic value of frailty on mortality at long-term follow-up of more than 5 years in patients 75 years or older hospitalised for non-ST-segment elevation myocardial infarction. We hypothesised that frailty is independently associated with long-term mortality. Design This was a prospective, observational study conducted at three centres. Methods and results Frailty was assessed according to the Canadian Study of Health and Aging clinical frailty scale (CFS). Of 307 patients, 149 (48.5%) were considered frail according to the study instrument (degree 5-7 on the scale). The long-term all-cause mortality of more than 5 years (median 6.7 years) was significantly higher among frail patients (128, 85.9%) than non-frail patients (85, 53.8%), (P amp;lt; 0.001). In Cox regression analysis, frailty was independently associated with mortality from the index hospital admission to the end of follow-up (hazard ratio 2.06, 95% confidence interval 1.51-2.81; P amp;lt; 0.001) together with age (P amp;lt; 0.001), ejection fraction (P = 0.012) and Charlson comorbidity index (P = 0.018). Conclusions In elderly non-ST-segment elevation myocardial infarction patients, frailty was independently associated with all-cause mortality at long-term follow-up of more than 6 years. The combined use of frailty and comorbidity may be the ultimate risk prediction concept in the context of cardiovascular patients with complex needs.
  •  
26.
  • Ekerstad, Niklas, et al. (författare)
  • Frailty is independently associated with 1-year mortality for elderly patients with non-ST-segment elevation myocardial infarction
  • 2014
  • Ingår i: European Journal of Preventive Cardiology. - : Sage Publications. - 2047-4873 .- 2047-4881. ; 21:10, s. 1216-1224
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: For the large population of elderly patients with cardiovascular disease, it is crucial to identify clinically relevant measures of biological age and their contribution to risk. Frailty is denoting decreased physiological reserves and increased vulnerability. We analysed the manner in which the variable frailty is associated with 1-year outcomes for elderly non-ST-segment elevation myocardial infarction (NSTEMI) patients. METHODS AND RESULTS: Patients aged 75 years or older, with diagnosed NSTEMI were included at three centres, and clinical data including judgment of frailty were collected prospectively. Frailty was defined according to the Canadian Study of Health and Aging Clinical Frailty Scale. Of 307 patients, 149 (48.5%) were considered frail. By Cox regression analyses, frailty was found to be independently associated with 1-year mortality after adjusting for cardiovascular risk and comorbid conditions (hazard ratio 4.3, 95% CI 2.4-7.8). The time to the first event was significantly shorter for frail patients than for nonfrail (34 days, 95% CI 10-58, p = 0.005). CONCLUSIONS: Frailty is strongly and independently associated with 1-year mortality. The combined use of frailty and comorbidity may constitute an important risk prediction concept in regard to cardiovascular patients with complex needs.
  •  
27.
  •  
28.
  • Ekerstad, Niklas, et al. (författare)
  • Frailty Is Independently Associated With Short-Term Outcomes for Elderly Patients With Non-ST-Segment Elevation Myocardial Infarction
  • 2011
  • Ingår i: Circulation. - Dallas, USA : American Heart Association. - 0009-7322 .- 1524-4539. ; 124:22, s. 2397-2404
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: For the large and growing population of elderly patients with cardiovascular disease, it is important to identify clinically relevant measures of biological age and their contribution to risk. Frailty is an emerging concept in medicine denoting increased vulnerability and decreased physiological reserves. We analyzed the manner in which the variable frailty predicts short-term outcomes for elderly non-ST-segment elevation myocardial infarction patients. Methods and results: Patients aged ≥ 75 years, with diagnosed non-ST-segment elevation myocardial infarction were included at 3 centers, and clinical data including judgment of frailty were collected prospectively. Frailty was defined according to the Canadian Study of Health and Aging Clinical Frailty Scale. The impact of the comorbid conditions on risk was quantified by the coronary artery disease-specific index. Of 307 patients, 149 (48.5%) were considered frail. By multiple logistic regression, frailty was found to be strongly and independently associated with risk for the primary composite outcome (death from any cause, myocardial reinfarction, revascularization due to ischemia, hospitalization for any cause, major bleeding, stroke/transient ischemic attack, and need for dialysis up to 1 month after inclusion) (odds ratio, 2.2; 95% confidence interval, 1.3-3.7) in-hospital mortality (odds ratio, 4.6; 95% confidence interval, 1.3-16.8), and 1-month mortality (odds ratio, 4.7; 95% confidence interval, 1.7-13.0). Conclusions: Frailty is strongly and independently associated with in-hospital mortality, 1-month mortality, prolonged hospital care, and the primary composite outcome. The combined use of frailty and comorbidity may constitute an ultimate risk prediciton concept in regard to cardiovascular patients with complex needs.
  •  
29.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • An imprint method to produce surface asperities for EHL and RCF experiments
  • 2020
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A method was developed for creating single well defined surface asperities using an imprint technique. The proposed method can be used to create asperities of different heights and widths in the micrometre range. The technique for creating single surface asperities is based on rolling a hard disc with indents against a soft disc. The contact pressure will cause plastic deformation forcing material into the indents to create the asperities. The height of the asperities can be controlled by adjusting the applied force. After initial reshaping during the run-in process, the asperities were strong enough to survive more than 35 million EHL contact cycles. The method should thus be of great interest for the researchers investigating rolling contact fatigue experimentally. The method could also aid the research of the run in process by enabling tracing the development of specific surface defects. Since the method can produce high and strong asperities it might also prove useful for investigations of exactly how asperities deform under sever contacts conditions.  
  •  
30.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • An imprint method to produce surface asperities for EHL and RCF experiments
  • 2021
  • Ingår i: MethodsX. - : Elsevier BV. - 1258-780X .- 2215-0161. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • A method was developed for creating single well-defined surface asperities using an imprint technique. The proposed method enables: • Creation of well-defined micrometre high asperities • Creation of asperities which survived more than 35 million EHL contact cycles • Damage tracing thanks to the possibility to control the damage initiation sites.The technique is based on rolling a hard disc with indents against a soft disc for creating single surface asperities. The contact pressure causes plastic deformation forcing material into the indents to create the asperities. The height of the asperities can be controlled by adjusting the applied force. After initial reshaping during the run-in process, the asperities were strong enough to survive more than 35 million elastohydrodynamic lubrication cycles, which should be of great interest for the researchers who investigate rolling contact fatigue experimentally. The method could also aid the research on the run-in process by enabling tracing the development of specific surface defects. Since the method can produce high and strong asperities it might also prove useful for investigations how asperities deform under sever contact conditions.
  •  
31.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • Contact fatigue initiation and tensile surface stresses at a point asperity which passes an elastohydrodynamic contact
  • 2018
  • Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 123, s. 234-255
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Contact mechanics and tribology was combined with fundamental fatigue and fracture mechanics to form a new mechanism for surface initiated rolling contact fatigue. Following, fatigue was investigated numerically for single asperities and craters in lubricated rolling contact surfaces. The hypothesis suggests that asperity point contacts can create sufficiently large tensile stresses for fatigue. The investigated case corresponded to a heavily loaded truck gear with ground surfaces. Reynolds equation resolved the elastohydrodynamic effect of the asperity in the transient three dimensional contacts. The Findley critical plane criterion was used for multiaxial and non-proportional fatigue evaluation. The simulations confirmed the new mechanism for rolling contact fatigue and showed how asperities can create contact fatigue in the lubricated contacts even without slip.
  •  
32.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • Experimental and numerical investigation of asperities and indents with respect to rolling contact fatigue
  • 2020
  • Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 151
  • Tidskriftsartikel (refereegranskat)abstract
    • Rolling contact experiments with slip were performed on artificial asperities and indents with pile-up. Micro-pits arose at the leading edge of the asperities and classic rolling contact fatigue (RCF) cracks initiated behind the trailing edge of the indents. The elastic-plastic run-in process and the thermal elastohydrodynamic lubrication (TEHL) load cycles were studied numerically. The run-in process caused high tensile residual stresses at the leading edge of the asperities while the TEHL load cycle caused high tensile stresses at the trailing edge of both the asperities and the indents. The conclusion was thus drawn that the classic RCF cracks behind the indents were caused by the TEHL load cycle while the micro-pits at these artificial asperities were caused by the tensile residual stresses from plastic deformation.
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33.
  • Everitt, Carl-Magnus, 1988- (författare)
  • Influence of surface roughness on rolling contact fatigue considering thermal elastohydrodynamic lubrication effects : Due to Corona it is not possible to attend this defense in person, instead attend via this link: https://play.kth.se/media/0_omfsppe6
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Rolling contacts are utilized in many technical applications, both in bearings and in the contacts between gear teeth. These components are subjected to high loads in many of their applications. The high loads causes very high contact pressures which may cause rolling contact fatigue, often denoted as pitting or spalling. This work focuses on the rolling contact fatigue mechanism of surface initiated pitting. Detailed simulations and experiments of rolling contacts have been performed in order to attain a better understanding of why pitting initiates and grows. The contact between two gears in a truck retarder was used as a case study. The investigated contact experienced elastohydrodynamic lubrication, EHL, conditions at which multiple pitting damages arose.Results from numerical investigations are presented in the papers A-C. In Paper A a numerical analysis of different measured surface topographies is presented showing that the sliding direction explains why more damage initiated down in the dedendum than up in the addendum. Detailed results of single artificial defects are presented in Paper B in order to explain the difference seen in Paper A. The results show that the defects subjected to negative slip break through the lubricant more and were thus subjected to higher friction. The analysis was extended to the conditions of the pitch line in Paper C and included variations of pressure, defect sizes, choice of lubricant and operational temperatures. The results presented in Paper C shows that the underlying theories of the asperity point load mechanism also predicts damage initiation at pure rolling, which agrees with the experiments on the truck retarder.A new imprint method for the manufacturing of well-defined micrometre high asperities in the surface of discs is presented in Paper D. The method was developed in order to enable experimental investigations of rolling contact fatigue. The manufactured asperities showed the potential to survive more than 35 million load cycles when tested in a twin-disc machine.An experimental and numerical investigation of micrometre high artificial asperities created with the imprint method is presented in Paper E. The experimental results showed that micro-pits developed on the leading edge of the highest asperities. The comparison with numerical simulations showed that the plastic deformations occurring during run-in there caused high tensile residual stresses in this region. Rolling contact fatigue, RCF, cracks initiated behind the trailing edge of the indents in the experiments. The simulations of the continued EHL testing, showed that these loads cased high tensile stresses in this region. The conclusion was hence drawn that the micro pits were caused by the residual stresses while the EHL loads caused the initiations of the RCF cracks.
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34.
  • Everitt, Carl-Magnus, 1988- (författare)
  • Initiation of rolling contact fatigue from asperities in elastohydrodynamic lubricated contacts
  • 2018
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Rolling contacts are utilized in many technical applications, both in bearings and in the contact between gear teeth. These components are often highly loaded, which makes them susceptible to suffer from rolling contact fatigue. This work focuses on the rolling contact fatigue mechanism of pitting. In order to attain a better understanding of why pitting initiates and grows, detailed simulations of rolling contacts have been performed. In particular the contact between two gears in a truck retarder was here used as a case study. The investigated contact experienced elastohydrodynamic lubrication conditions since the load was high enough to causes the surfaces in contact to deform and the viscosity of the lubricant to increase significantly.In Paper A it was investigated if surface irregularities in the size of the surface roughness are large enough to cause surface initiated fatigue. The investigation focused on the pitch line since small surface initiated pits were found here even though there was no slip present. Since there were pits present at the pitch line, it is important that the theories of pitting can explain the development of pits also in the absence of slip. The conclusion of the work was that surface irregularities of the size of normal surface roughness are enough to cause surface initiated fatigue at the pitch line.In Paper B it was investigated why pits are more likely to initiate in the dedendum of pinion gears than in the addendum. In both areas slip is present but in different directions. In the dedendum the friction from slip is against the rolling direction which enhances the risk for pitting. The investigation was performed by studying the effect of the temperature rise in the contact caused by the slip. The conclusion drawn was that the temperature rise in the contact explained why pitting was more common in the dedendum than in the addendum.
  •  
35.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • Investigation of the asperity point load mechanism for thermal elastohydrodynamic conditions
  • 2019
  • Ingår i: ICMFF12 - 12th international conference on multiaxial fatigue and fracture. - : E D P SCIENCES.
  • Konferensbidrag (refereegranskat)abstract
    • The rolling contact fatigue damage called pitting or spalling develops more frequently in surfaces with negative than positive slip. Since normal line loads do not cause any tensile surface stresses this investigation considers the effects of small point shaped asperities. Shear traction causes tensile stresses at the trailing edge of asperities entering the contact at negative slip. At positive slip the tensile stresses appear at the leading edge when the asperities exit the contact. It was found that the trailing edge of the asperity breaks through the lubrication film at contact entry. This causes negative slip to be more detrimental than positive slip. At negative slip the location of large frictional shear stresses and tension stresses from normal asperity contact coincide.
  •  
36.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • Surface initiation of rolling contact fatigue at asperities considering slip, shear limit and thermal elastohydrodynamic lubrication
  • 2019
  • Ingår i: Tribology International. - : Elsevier Ltd. - 0301-679X .- 1879-2464. ; 137, s. 76-93
  • Tidskriftsartikel (refereegranskat)abstract
    • A numerical investigation was performed, with single axisymmetric asperities passing through lubricated rolling contacts at different slip. Two explanatory and cooperating phenomena were found as to why the damage develops more frequently at negative than positive slip. Metal contact occurred in the inlet, where tractive asperity contacts at negative slip provided a large tensile surface stress outside the contact. As the asperity moved through the contact, sliding supplied it with lubricant and heated the lubricant along the contact. The shear tractions were thus higher near the inlet than the outlet, making them more detrimental for negative than positive slip.
  •  
37.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • The asperity point load mechanism for rolling contact fatigue considering slip and thermal elastohydrodynamic lubrication
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Rolling contact fatigue was investigated numerically for a single asperity and crater passing through lubricated rolling contacts with slip. The purposes was to explain why rolling contact fatigue pits develop in the forward rolling direction when slip is negative and to further verify the asperity point load mechanism for pitting. The simulations included thermal effects from friction and compression of the lubricant. It was concluded that heating of the lubricant decreased the viscosity and the contact shear stress profile in the second half of the contact, which provided an asymmetric stress profile and explained the pitting damage behaviour in relation to slip direction. 
  •  
38.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • The influence of gear surface roughness on rolling contact fatigue under TEHL conditions with slip
  • 2020
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Measured shot peened, ground and worn surfaces were included in thermal elastohydrodynamic lubrication and fatigue simulations. Considering transient temperature fields, shear limit and metal to metal contact, moderate negative slip was found to be more detrimental than positive. The location of pitting in gears was thus explained by the surface roughness and the slide to roll ratio. The λ -ratio correlated with fatigue risk within each surface structure. As a supplement to the λ -ratio the surface skewness qualitatively ranked the fatigue risk between the surface structures. 
  •  
39.
  • Everitt, Carl-Magnus, 1988-, et al. (författare)
  • The influence of gear surface roughness on rolling contact fatigue under thermal elastohydrodynamic lubrication with slip
  • 2020
  • Ingår i: Tribology International. - : Elsevier Ltd. - 0301-679X .- 1879-2464. ; 151
  • Tidskriftsartikel (refereegranskat)abstract
    • Measured shot peened, ground and worn surfaces were included in thermal elastohydrodynamic lubrication and fatigue simulations. Considering transient temperature fields, shear limit and metal to metal contact, moderate negative slip was found to be more detrimental than positive. The location of pitting in gears was thus explained by the surface roughness and the slide to roll ratio. The λ-ratio correlated with fatigue risk within each surface structure. As a supplement to the λ-ratio the surface skewness qualitatively ranked the fatigue risk between the surface structures.
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40.
  • Gustavsson, Martin G. H., et al. (författare)
  • Research & Innovation Platform for Electric Road Systems
  • 2021
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • The Swedish government has prioritized achieving a fossil fuel-independent vehicle fleet by 2030 which will require radical transformation of the transport industry. Electrifying the vehicle fleet forms an important part of this transformation. For light vehicles, electrification using batteries and charging during parking is already well advanced. For city buses, charging at bus stops and bus depots is being developed, but for heavy, long-distance road transport, batteries with enough capacity to provide sufficient range would be too cumbersome and too much time would have to be spent stationary for charging.One solution might be the introduction of electric roads, supplying the moving vehicle with electricity both to power running and for charging. In the longer term, this approach could also be used for light vehicles and buses.The objective of the Research and Innovation Platform for Electric Roads was to enhance Swedish and Nordic research and innovation in this field, this has been done by developing a joint knowledge base through collaboration with research institutions, universities, public authorities, regions, and industries.The work of the Research and Innovation Platform was intended to create clarity concerning the socioeconomic conditions, benefits, and other effects associated with electric roads. We have investigated the benefits from the perspectives of various actors, implementation strategies, operation and maintenance standards, proposed regulatory systems, and factors conducive of the acceptance and development of international collaborative activities.The project commenced in the autumn of 2016 and the main research continued until December 2019, the work during year 2020 has been focused on knowledge spread and coordination with the Swedish-Germany research collaboration on ERS (CollERS). The results of the Research and Innovation Platform have been disseminated through information meetings, seminars, and four annual international conferences. Reports have been published in the participating partners’ ordinary publication series and on www.electricroads.org. The project was funded by Strategic Vehicle Research and Innovation (FFI) and the Swedish Transport Administration.
  •  
41.
  • Henriksson, Lilian, et al. (författare)
  • The transluminal attenuation gradient does not add diagnostic accuracy to coronary computed tomography
  • 2021
  • Ingår i: Acta Radiologica. - : Sage Publications. - 0284-1851 .- 1600-0455. ; , s. 867-874
  • Tidskriftsartikel (refereegranskat)abstract
    • Background A method for improving the accuracy of coronary computed tomography angiography (CCTA) is highly sought after as it would help to avoid unnecessary invasive coronary angiographies. Measurement of the transluminal attenuation gradient (TAG) has been proposed as an alternative to other existing methods, i.e. CT perfusion and CT fractional flow reserve (FFR). Purpose To evaluate the incremental value of three types of TAG in high-pitch spiral CCTA with invasive FFR measurements as reference. Material and Methods TAG was measured using two semi-automatic methods and one manual method. A receiver operating characteristic (ROC) analysis was made to determine the usefulness of TAG alone as well as TAG combined with CCTA for detection of significant coronary artery stenoses defined by an invasive FFR value <= 0.80. Results A total of 51 coronary vessels in 37 patients were included in this retrospective study. Hemodynamically significant stenoses were found in 13 vessels according to FFR. The ROC analysis TAG alone resulted in areas under the curve (AUCs) of 0.530 and 0.520 for the semi-automatic TAG and 0.557 for the manual TAG. TAG and CCTA combined resulted in AUCs of 0.567, 0.562 for semi-automatic TAG, and 0.569 for the manual TAG. Conclusion The results from our study showed no incremental value of TAG measured in single heartbeat CCTA in determining the severity of coronary artery stenosis degrees.
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42.
  • Holm, Anna, 1973-, et al. (författare)
  • Long term risk and costs of bleeding in men and women treated with triple antithrombotic therapy : An observational study
  • 2021
  • Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 16:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives Bleeding is the most common non-ischemic complication in patients with coronary revascularisation procedures, associated with prolonged hospitalisation and increased mortality. Many factors predispose for bleeds in these patients, among those sex. Anyhow, few studies have characterised the population receiving triple antithrombotic therapy (TAT) as well as long term bleeds from a sex perspective. We investigated the one year rate of bleeds in patients receiving TAT, potential sex disparities and premature discontinuation of TAT. We also assessed health care costs in bleeders vs non-bleeders. Setting Three hospitals in the County of ostergotland, Sweden during 2009-2015. Participants All patients discharged with TAT registered in the SWEDEHEART registry. Primary and secondary outcome measures All bleeds receiving medical attention during one-year follow-up were collected by retrieving relevant information about each patient from medical records. Resource use associated with bleeds was assigned unit cost to estimate the health care costs associated with bleeding episodes. Results Among 272 patients, 156 bleeds occurred post-discharge, of which 28.8% were gastrointestinal. In total 54.4% had at least one bleed during or after the index event and 40.1% bled post discharge of whom 28.7% experienced a TIMI major or minor bleeding. Women discontinued TAT prematurely more often than men (52.9 vs 36.1%, p = 0.01) and bled more (48.6 vs. 37.1%, p = 0.09). One-year mean health care costs were EUR 575 and EUR 5787 in non-bleeding and bleeding patients, respectively. Conclusion The high bleeding incidence in patients with TAT, especially in women, is a cause of concern. There is a need for an adequately sized randomised, controlled trial to determine a safe but still effective treatment for these patients.
  •  
43.
  • Holm, Anna, 1973-, et al. (författare)
  • Sex differences in platelet reactivity in patients with myocardial infarction treated with triple antiplatelet therapy-results from assessing platelet activity in coronary heart disease (APACHE)
  • 2021
  • Ingår i: Platelets. - : Taylor & Francis. - 0953-7104 .- 1369-1635. ; 32:1, s. 524-532
  • Tidskriftsartikel (refereegranskat)abstract
    • )Several earlier studies have reported increased risk of bleeding in women with myocardial infarction, (MI) compared to men. The reasons for the observed difference are incompletely understood, but one suggested explanation has been excess dosing of antithrombotic drugs in women. The aim of this prospective observational study was to assess sex differences in platelet activity in patients treated with three different platelet inhibitors. We recruited 125 patients (37 women and 88 men) with MI, scheduled for coronary angiography. All patients received clopidogrel and aspirin. A subgroup of patients received glycoprotein (GP) IIb/IIIa-inhibitor. Platelet aggregation in whole blood was assessed at several time points, using impedance aggregometry. SolubleP-selectin was measured 3 days after admission. There were no significant differences between women and men in baseline features or comorbidities except higher frequency of diabetes, lower hemoglobin value, and lower estimated glomerular filtration rate, in women on admission. We observed significantly more in-hospital bleeding events in women compared to men (18.9% vs. 6.8%,p= .04). There were no differences in platelet aggregation using three different agonists, reflecting treatment effect of GPIIb/IIIa-inhibitors, clopidogrel, and aspirin, 6-8 hours, 3 days, 7-9 days, or 6 months after loading dose. Moreover, there was no significant difference in solubleP-selectin. The main finding of this study was a consistent lack of difference between the sexes in platelet aggregation, using three different agonists at several time-points. Our results do not support excess dosing of anti-platelet drugs as a major explanation for increased bleeding risk in women.
  •  
44.
  • Hössjer, Ola, et al. (författare)
  • Quantifying and estimating additive measures of interaction from case-control data
  • 2017
  • Ingår i: Modern stochastics: theory and applications. - 2351-6054. ; 4:2, s. 109-125
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we develop a general framework for quantifying how binary risk factors jointly influence a binary outcome. Our key result is an additive expansion of odds ratios as a sum of marginal effects and interaction terms of varying order. These odds ratio expansions are used for estimating the excess odds ratio, attributable proportion and synergy index for a case-control dataset by means of maximum likelihood from a logistic regression model. The confidence intervals associated with these estimates of joint effects and interaction of risk factors rely on the delta method. Our methodology is illustrated with a large Nordic meta dataset for multiple sclerosis. It combines four studies, with a total of 6265 cases and 8401 controls. It has three risk factors (smoking and two genetic factors) and a number of other confounding variables.
  •  
45.
  • Lawesson, Sofia, et al. (författare)
  • Gender difference in prevalence and prognostic impact of renal insufficiency in patients with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention
  • 2011
  • Ingår i: Heart. - : BMJ Publishing Group; 1999. - 1355-6037 .- 1468-201X. ; 97:4, s. 308-314
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective To evaluate if female gender is associated with renal insufficiency in patients with ST-elevation myocardial infarction (STEMI) and if there is a gender difference in the prognostic importance of renal insufficiency in STEMI. Design Single-centre observational study. Setting One tertiary cardiac centre. Patients All consecutive patients with STEMI planned for primary percutaneous coronary intervention in one Swedish county in 2005 (98 women and 176 men). Main outcome measures Logistic regression analyses were conducted to evaluate the predictors of renal insufficiency, associations between estimated glomerular filtration rate (eGFR) and outcome in each gender and a possible interaction between gender and eGFR regarding outcome. Results Renal insufficiency was defined as eGFR less than 60 ml/min per 1.73 m(2). 67% of women had renal insufficiency compared with 26% of men, OR 5.06 (95% CI 2.66 to 9.59) after multivariable adjustment. In women each 10 ml/min per 1.73 m 2 increment of eGFR was associated with a 63% risk reduction for 1-year mortality, OR 0.37 (95% CI 0.15 to 0.89). No such association was found in men, OR 1.05 (95% CI 0.63 to 1.76). A trend towards a significant interaction between gender and eGFR regarding 1-year mortality was found, OR 2.05 (95% CI 0.93 to 4.50). Conclusions A considerable gender difference in the prevalence of renal insufficiency in STEMI was found and renal insufficiency seemed to be a more important prognostic marker in women. These results are important as previous STEMI studies have shown higher multivariable adjusted mortality in women than in men but renal function has seldom been taken into consideration.
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46.
  • Magnusson, Carl, 1976, et al. (författare)
  • Difficulties in the prehospital assessment of patients with TIA/stroke
  • 2021
  • Ingår i: Acta Neurologica Scandinavica. - : Hindawi Limited. - 0001-6314 .- 1600-0404. ; 143:3, s. 318-325
  • Tidskriftsartikel (refereegranskat)abstract
    • Background In patients with TIA/stroke, early assessment is critical. Aim To describe patients who were not directly transported to hospital by ambulance after prehospital assessment. Methods Patients hospitalized with TIA/stroke in Gothenburg, Data were obtained from the EMS and hospital case record system. Results There were 7,812 patients with TIA/stroke, of which 4,853 (62%) were candidates for EMS transport. Among them, 176 (3.6%) were not directly transported to hospital by ambulance. In 45% of them, delay from symptom onset to calling for EMS was <= 24 hours. On EMS arrival, common symptom was dizziness (28%), followed by weakness in arm or leg (21%), loss of sensibility (13%), speech disturbances (7%), and facial numbness (4%). The modified National Institute of Health Stroke Score (mNIHSS) was 0 in 80% and >1 in two per cent. The NIHSS at the emergency department was 1-4 in 39% and 5-15 in six per cent. The EMS clinician made the decision not to transport the patient to hospital by the EMS in 84%, the dispatcher in 12% and the patient or relatives in four per cent. Patients were involved in the decision in 51%. Final diagnosis was stroke in 74% and the proportion who were independent in normal daily activities at hospital discharge decreased by 15% compared with before event. Conclusion About 3%-4% of patients with TIA/stroke were not directly transported to hospital by EMS after prehospital assessment. The most common symptom was dizziness. Decision-support tools for EMS to identify time-sensitive conditions are required.
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47.
  • Mohr, Matthias, et al. (författare)
  • Wind power in forests II : Forest wind
  • 2018
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Sweden has good conditions for wind power. However, most of Sweden (ca. 70%) is covered by forest. Forests decrease wind speeds and create turbulence, something which is not favourable for wind power. Several Swedish wind maps have shown that forests in Nordic countries can be well suited for wind power (e.g. Bergström and Söderberg 2011, Byrkjedal and Åkervik 2009).At the same time, there is uncertainty over wind conditions over forests at very high altitudes (ca. 150 m above ground). How good do wind resource assessment models agree with measurements? How much energy is a wind turbine in forest going to produce and which loads will a wind turbine in forest experience?This project has investigated all these issues. Work was concentrated in the following work packages:Wind resource at very high heightsTurbulence- and wind measurements at very high heights above forestAnalysis of turbulence data from forestsModel simulations with wind flow modelsModel simulations with very-high-resolution weather forecast modelsModel simulations with Large Eddy Simulation (LES) modelsImproved specification of so-called “synthetic turbulence” over forestAnalysis of airborne laser altimeter measurements over forestForest’s effects on wind turbine energy productionLoad simulations for wind turbines over forestWP1 studies how wind speed and direction varies with height over forest (up to ca 150 m above ground and higher up). Several profile relations are studied here.  Frequency distributions of wind shear and veer are presented. WP2 describes turbulence and wind measurements that have been carried out within the project at Hornamossen. Moreover, the measurement campaign that was carried out in a line over the Hornamossen-hill within the New European Wind Atlas project is described. WP3 analyses turbulence data from Hornamossen together with turbulence data from Ryningsnäs. Of special interest is how turbulence intensity decreases with height as well as if the IEC-standard class A, B or C for wind turbines is complied with at different heights. WP4 describes the newly developed linearised wind flow model ORFEUS with a dedicated forest module. WP5 describes model simulations with WRF and the MIUU model, their sensitivity for surface roughness and turbulence parameterisations. Mean wind profiles from the models are compared to Hornamossen. WP6 describes LES simulations with Chalmers LES model and WRF-LES. LES-resultats depend to a large degree on how the turbulent vortices are initialised at the inflow boundaries of the LES model. Several different methods for that are described. WP7 describes a new turbulence model (the Segalini & Arnqvist model) that includes atmospheric stability. This is a further development of the IEC turbulence model (=Mann model) for neutral stability. Coherence of turbulent winds as well as phase profiles are other improvements of the IEC model. WP8 describes a new method to compute leaf/needle/plant area density from laser scans of the Swedish forest and how one estimates surface roughness and zero plane displacement from that. The new method is compared with two other methods. Results are also compared with official forest data (“skoglig grunddata”). The effect on the wind profile is also shown. WP9 describes the new methods for estimating AEP from the Power Curve Working Group and the IEC standard for Power Performance Testing. Effects on estimated AEP are shown. A new simple model for calculating turbulence effects on energy production is developed and compared with data from a wind farm. Within WP10 a new generic open-source wind turbine is developed and used for load simulations with aero-elastic simulations. Results show that the new coherence model for turbulence gives much smaller loads than the turbulence model of the IEC standard.For more information on the different parts of the project the reader is referred to the report’s introduction, the ”Summary and Conclusions” of each chapter as well as the overall summary (”Executive Summary”) at the end of the report.
  •  
48.
  • Sandstedt, Mårten, 1972- (författare)
  • Computed Tomography of the Coronary Arteries : Developmental and Prognostic Investigations
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Computed tomography (CT) is an increasingly used modality for investigations of patients with suspected coronary artery disease (CAD). Technical advances could improve diagnostic accuracy and lead to clinical workflow improvements. Also, more prognostic information can optimize clinical follow-up strategies and treatments.The general aim of this thesis was to explore the use of CT for CAD investigations. Three studies aimed to examine new technologies, including the evaluation of an on-site, computed tomography-based fractional flow reserve (CT-FFR) software (study I), the evaluation of an AI-based, calcium scoring computed tomography (CSCT) software (study III), and the evaluation of an photon-counting detector (PCD)-CT (study IV). One study aimed to evaluate the long-term prognostic value of coronary computed tomography angiography (CCTA) in symptomatic patients with no history of CAD (study II).The software evaluation studies (study I and III) and the prognostic study (study II) utilized CT data from clinical patients, while the PCD-CT evaluation study (study IV) used CT data from cadaveric specimens. The performances of both software programs were compared with standard references, being represented by fractional flow reserve (FFR) measurements (study I), and coronary artery calcification (CAC) scores from a semi-automatic software (study III), respectively. The PCD-CT performance on CAC quantification was compared with corresponding results from an energy integrating detector (EID)-CT, using micro-CT as the standard reference (study IV). The prognostic study merged registries to identify major adverse cardiac events (MACE), having a follow-up time of up to 7.5 years (study II).The CT-FFR and CSCT software correlation and agreement to corresponding standard references were good and excellent, respectively. Also, both software programs had time-saving potential (study I and III). The CAC quantification was more accurate using PCD-CT than EID-CT (study IV). The prognosis was excellent in patients with normal coronary arteries, and progressively impaired in non-obstructive and obstructive CAD (study II).The results in this thesis convey developmental, technical CT technology advances for CAD investigations. In addition, prognostic follow-up data is communicated. The results may benefit patients by an increased accuracy in the CT evaluation of CAD and can contribute to improve clinical follow-up strategies. Furthermore, the results suggest possibilities to improve the workflow in clinical radiology, which potentially could impact health care costs.
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49.
  • Sandstedt, Mårten, 1972-, et al. (författare)
  • Evaluation of an AI-based, automatic coronary artery calcium scoring software
  • 2020
  • Ingår i: European Radiology. - : Springer. - 0938-7994 .- 1432-1084. ; 30:3, s. 1671-1678
  • Tidskriftsartikel (refereegranskat)abstract
    • ObjectivesTo evaluate an artificial intelligence (AI)–based, automatic coronary artery calcium (CAC) scoring software, using a semi-automatic software as a reference.MethodsThis observational study included 315 consecutive, non-contrast-enhanced calcium scoring computed tomography (CSCT) scans. A semi-automatic and an automatic software obtained the Agatston score (AS), the volume score (VS), the mass score (MS), and the number of calcified coronary lesions. Semi-automatic and automatic analysis time were registered, including a manual double-check of the automatic results. Statistical analyses were Spearman’s rank correlation coefficient (⍴), intra-class correlation (ICC), Bland Altman plots, weighted kappa analysis (κ), and Wilcoxon signed-rank test.ResultsThe correlation and agreement for the AS, VS, and MS were ⍴ = 0.935, 0.932, 0.934 (p < 0.001), and ICC = 0.996, 0.996, 0.991, respectively (p < 0.001). The correlation and agreement for the number of calcified lesions were ⍴ = 0.903 and ICC = 0.977 (p < 0.001), respectively. The Bland Altman mean difference and 1.96 SD upper and lower limits of agreements for the AS, VS, and MS were − 8.2 (− 115.1 to 98.2), − 7.4 (− 93.9 to 79.1), and − 3.8 (− 33.6 to 25.9), respectively. Agreement in risk category assignment was 89.5% and κ = 0.919 (p < 0.001). The median time for the semi-automatic and automatic method was 59 s (IQR 35–100) and 36 s (IQR 29–49), respectively (p < 0.001).ConclusionsThere was an excellent correlation and agreement between the automatic software and the semi-automatic software for three CAC scores and the number of calcified lesions. Risk category classification was accurate but showing an overestimation bias tendency. Also, the automatic method was less time-demanding.Key Points• Coronary artery calcium (CAC) scoring is an excellent candidate for artificial intelligence (AI) development in a clinical setting.• An AI-based, automatic software obtained CAC scores with excellent correlation and agreement compared with a conventional method but was less time-consuming.
  •  
50.
  • Sandstedt, Mårten, et al. (författare)
  • Long-term prognostic value of coronary computed tomography angiography in chest pain patients.
  • 2019
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 60:1, s. 45-53
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Coronary computed tomography angiography (CCTA) is increasingly used to detect coronary artery disease (CAD), but long-term follow-up studies are still scarce. Purpose To evaluate the prognostic value of CCTA in patients with suspected CAD. Material and Methods A total of 1205 consecutive CCTA patients with chest pain were classified as normal coronary arteries, non-obstructive CAD, or obstructive CAD. The primary outcome was major adverse cardiac event (MACE), defined as a composite outcome including cardiac death, myocardial infarction, unstable angina pectoris, or late revascularization (after >90 days). Results Over 7.5 years follow-up (median = 3.1 years), Kaplan-Meier estimates demonstrated a MACE in 1.0%, 4.6%, and 20.7% in normal coronary arteries, non-obstructive CAD, and obstructive CAD, respectively. Log rank test for pairwise comparisons showed significant differences between non-obstructive CAD and normal coronary arteries ( P = 0.023) and between obstructive CAD and normal coronary arteries ( P < 0.001). In a multivariable analysis, adjusting for classical risk factors, non-obstructive CAD and obstructive CAD were independent predictors of MACE, with hazard ratios (HR) of 3.22 ( P = 0.041) and 25.18 ( P < 0.001), respectively. Conclusion Patients with normal coronary arteries have excellent long-term prognosis, but the risk for MACE increases with non-obstructive and obstructive CAD. Both non-obstructive and obstructive CAD are independently associated with future ischemic events.
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