| 1. |
- Carlén, Anna, 1985-
(författare)
-
Exercise Testing in Firefighters : Work Capacity and Cardiovascular Risk Assessment in a Low-Risk Population
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background. Firefighting is one of the most physically demanding occupations and it requires a high cardiorespiratory fitness level.Pre-duty medical evaluation of firefighters includes fitness testing and assessment of cardiac health to ensure that firefighters meet the minimum physical fitness standard and to ensure that they are not at increased risk of cardiac events. The medical evaluation methods for Swedish firefighters are regulated by the Swedish Work Environment Authority and include a 6 min constant workload treadmill (TM) test for fitness evaluation in which the firefighter wears full smoke diving equipment and a maximal effort exercise electrocardiography test (ExECG) at cycle ergometer (CE) for assessment of cardiac health. Previously, fitness was also evaluated by cycle ergometry.The standard parameter for evaluation of ischaemic heart disease (IHD) is exercise-induced ST depression. In general, exercise testing of asymptomatic low-risk individuals is discouraged due to low sensitivity and specificity for IHD, generating both false-positive and false-negative test results. Heart rate (HR) adjustment of the ST-segment response has been shown to be superior to simple ST depression to evaluate cardiac ischaemia in some populations, but has not been extensively evaluated in an occupational setting.Methods. We retrospectively analysed a cohort of 774 firefighters who were asymptomatic at the time of the testing.In paper I, test approval, HR response, and calculated oxygen uptake from TM tests and CE tests for 424 firefighters (44±10 years) were compared.Paper II methodologically described the process for data extraction, processing, and calculation of ExECG data from a clinical database. Procedures for noise assessment, error checking, and computerized calculation of ST/HR parameters were described.In paper III, ExECG and medical records of 521 male firefighters (44±10 years) were studied. During 8.4 ± 2.1 years of follow-up, IHD was verified angiographically in 12 subjects. The predictive value of HR-adjusted ST variables (ST/HR index, ST/HR slope, and ST/HR loop) for IHD was evaluated.In paper IV, subjects with objectively verified IHD were excluded and factors associated with exercise-induced nonischaemic ST depression were studied in the remaining 509 males (46±11 years). Results. The firefighters had an average maximal exercise capacity of 281 ± 36 W (range 186-467 W) achieved by incremental CE exercise. To enable comparison, the maximal workload was converted to the workload sustainable for 6 min. It was more common to pass the 6 min TM fitness test but to fail the supposedly equivalent CE test rather than vice versa.Twenty percent of the firefighters developed an ST depression of ≥o.1 mV in at least one lead during exercise and half of the firefighters had a horizontal or downsloping ST depression. While an abnormal ST response associated with an increased risk for IHD only in V4, both an abnormal ST/HR index and an abnormal ST/HR slope associated with IHD in three leads each. Clockwise rotation of the ST/HR loop was infrequent in all precordial leads (1%), but it associated with an increased risk for IHD.In the subgroup without evidence of coronary artery disease, age and the HR response associated with ST depression, whereas hypertension, hyperlipidaemia, diabetes, blood pressure response, and exercise capacity did not. Conclusions. Even though the calculated oxygen uptake was higher for the TM test than for the supposedly equivalent CE test, the higher treadmill approval rate may indicate that the fitness requirement for Swedish firefighters has been lowered by changing the test modality.Exercise-induced ST depression was common in asymptomatic physically active men, although there were only a few cases of IHD during follow-up. If performing ExECG in asymptomatic, low-risk populations, ST/HR analysis could be given more importance. However, the limited clinical value of ExECG in low-risk populations was emphasised and needs to be reconsidered.In asymptomatic, physically active men without coronary artery disease, false-positive ST depressions can be partially explained by HR variables rather than by common cardiovascular risk factors and blood pressure response to exercise.
|
|
| 2. |
- Forsberg, Lena, 1983-
(författare)
-
Cardiac Function and Aortic Valve Intervention : Echocardiographic Studies of Myocardial Recovery in Patients with Severe Aortic Valve Disease
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In patients with severe aortic valve disease, aortic valve intervention is performed when the risk for mortality or morbidity with conservative management is significantly increased. Left ventricular (LV) longitudinal motion decreases before conventional echocardiographic measures such as ejection fraction, are influenced in patients with severe aortic valve disease. This thesis is devoted to the assessment of cardiac function, including ventricular longitudinal motion, by echocardiography before and after aortic valve intervention in patients with chronic severe aortic regurgitation (AR) or severe aortic stenosis (AS).Patients with chronic AR (n=29) were studied preoperatively, and 6 months and 4 years postoperatively by echocardiography, including tissue Doppler imaging, at rest and during exercise. LV longitudinal function (atrioventricular plane displacement, AVPD, and peak systolic velocity, PSV) decreased postoperatively, and patients with low PSV continued to show reduced longitudinal function 6 months after surgery. Preoperative exercise echocardiographic variables showed a strong correlation to late LV function variables, while preoperative variables obtained at rest were not useful for prediction. Exercise echocardiography and longitudinal LV function could therefore be useful complements in the timing of aortic valve surgery for AR.Patients with chronic AR (n=29) were studied preoperatively, and 6 months and 4 years postoperatively by echocardiography, including tissue Doppler imaging, at rest and during exercise. LV longitudinal function (atrioventricular plane displacement, AVPD, and peak systolic velocity, PSV) decreased postoperatively, and patients with low PSV continued to show reduced longitudinal function 6 months after surgery. Preoperative exercise echocardiographic variables showed a strong correlation to late LV function variables, while preoperative variables obtained at rest were not useful for prediction. Exercise echocardiography and longitudinal LV function could therefore be useful complements in the timing of aortic valve surgery for AR.
|
|
| 3. |
- Fyrenius, Anna, 1969-
(författare)
-
Dynamiskt lärande : En ämnesdidaktisk avhandling om fysiologiska fenomen och läkarstudentens lärande
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that the outcome of teaching and learning in higher education is often unsatisfactory. Earlier studies have shown that medical students often have a surface approach to their studies and that misconceptions of fundamental physiological phenomena are common. The aim of this thesis is to support educational practice in medicine, particularly in medical physiology. The thesis can be categorised as subject matter-specific education research, which means that questions about teaching and learning are closely linked to the subject studied. The researcher should be well acquainted with the subject in question. The subject area dealt with in this thesis is physiological phenomena related to cardiovascular pressure-flow relations.The thesis consists of studies of 3-dimensional intra cardiac pressure-flow phenomena in the heart (studies 1 and 2) and studies of how students conceive of and develop an understanding of physiological phenomena related to blood pressure and blood pressure regulation (studies 3 and 4).Flow in the left atrium as well as inflow-patterns to the left ventricle were studied. The 3-dimensional method elucidates vortical flow phenomena which were previously unknown. The findings could contribute to increasing physicians and technicians understanding of flow phenomena in the diagnosis and assessment of heart disease and to the further development of diagnostic methods. In the studies of learning and understanding of physiological phenomena, the findings point to new aspects of a deep approach to learning, which have to do with the students’ ability to change perspective and adopt a variety of learning strategies to a phenomenon (Moving) versus a tendency to hold on to one explanatory model (Holding). The study also investigates the students’ ability to identify and apply fundamental physiological principles as well as how they conceive of the importance of detailed knowledge for understanding of physiology. The findings point to differences in the students’ conceptions of physiological principles. A problemising approach, which includes not only causally described relations, indicates a more complex conception of physiological phenomena. The study shows aspects of understanding which are seldom assessed in examinations.The findings indicate a connection between the students’ approaches to learning and the quality of their understanding of fundamental physiological principles. In the thesis, teaching interventions are proposed in order to stimulate dynamic learning and a learning environment where students are not afraid to challenge their conceptions in order to acquire a rich and nuanced picture of physiological phenomena.
|
|
| 4. |
- Hedman, Kristofer, 1984-
(författare)
-
Cardiac function and long-term volume load : Physiological investigations in endurance athletes and in patients operated on for aortic regurgitation
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background and aims. The heart is a remarkably adaptable organ, continuously changing its output to match metabolic demands and haemodynamic load. But also in long-term settings, such as in chronic or repeated volume load, there are changes in cardiac dimensions and mass termed cardiac hypertrophy. Depending on the stimulus imposing the volume load this hypertrophy differs in extent and phenotype. We aimed to study cardiac function in two settings with long-term volume load, including patients previously operated for aortic regurgitation and healthy females performing endurance training.Methods. In paper I, 21 patients (age 52±12 years, all male) operated on with aortic valve replacement for aortic regurgitation (AR) underwent a cardiopulmonary exercise test (CPET) and an echocardiographic evaluation in average 49±15 months following surgery. The peak oxygen uptake (peakVO2) was compared to results from a pre-operative and a six months follow-up, and relations to echocardiographic measures were determined.In papers II–IV, 48 endurance trained female athletes (ATH, age 21±2 years) were compared to 46 untrained females (CON, age 21±2 years) regarding echocardiographic measures of cardiac dimensions, global and regional cardiac function and maximal aerobic capacity (VO2max) determined with CPET. Relations between VO2max and cardiac variables were explored.Results. In paper I, peakVO2 had decreased from 26±6 to 23±5 mL/kg/min in patients from the first to second, late follow-up. This decrease was larger than expected by their increased age alone, and a majority of patients had a cardiorespiratory fitness below average according to reference values from healthy subjects of the same age, sex and weight.In papers II–IV, we found that ATH (VO2max 52±5 mL/kg/min) had larger atrial, ventricular and inferior vena cava dimensions compared to CON (VO2max 39±5 mL/kg/min). ATH had increased measures of right ventricular (RV) systolic function (RV atrioventricular plane displacement indexed by cardiac length 2.5±0.3 vs. 2.3±0.3, p=0.001) and left ventricular (LV) diastolic function (mitral E-wave velocity 0.92±0.17 vs. 0.86±0.11 m/s, p=0.029). In addition, systolic synchrony was similar between groups while there were heterogeneous differences in diastolic and systolic function across different myocardial segments. VO2max was most strongly related to LV end-diastolic volume (r=0.709, p<0.001).Conclusions. Decreasing peakVO2 following surgery for AR, despite a normalisation in cardiac dimension could either be a result of a remaining, slight myocardial dysfunction or post-operative negative influence on cardiac performance by filling disturbances or the prosthetic valve itself, or, a sign of an inadequate post-operative level of physical activity and lack of exercise training. This stresses the importance of post-operative management and methods for increasing aerobic capacity, where exercise testing could be valuable for guiding patients and tailoring exercise protocols.The eccentric cardiac hypertrophy in ATH, symmetrically distributed across the heart, depicts the physiological hypertrophy in response to volume load in endurance training. Cardiac function was similar, or for some measures slightly improved in ATH compared to CON and LV dimensions, rather than cardiac function, were predictors of VO2max. As the heart of female athletes has been far less studied than that in males, our results add knowledge regarding the female athlete’s heart, and our results of differences in segmental cardiac function merits further research.
|
|
| 5. |
- Lans, Charlotta, 1965-
(författare)
-
Exercise training and testing in patients with heart failure
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Patients with heart failure (HF) suffer from symptoms such as dyspnea, fatigue and reduced quality of life, which affect their physical function and often lead to immobilization and poor survival prognosis. Exercise training in cardiac rehabilitation should be offered to every patient with HF and can be performed both in a hospital-setting and with a home training programme. Exercise, in patients with HF, improves physical function and functional capacity as well as health-related quality of life (HRQoL) and reduces the need for hospital care. There are several barriers against participating in exercise based cardiac rehabilitation despite information about its benefits. The patient may anticipate not being able to exercise, that the exercise would be too hard, lives far away or has not been referred.Aim: The aim of this thesis was to evaluate the effects of exercise in heart failure patients, of a one-year training programme, with hospital-based training followed by a home-based setting or only home-based, with special emphasis on peripheral muscle training (PMT). Furthermore, to study frequently used methods for evaluation of the effects, i.e the 6-minute walk test and instruments for estimating health-related quality of life.Methods and findings: In study I, PMT was evaluated and the PMT programme in a hospital-setting (with equipment) and subsequent homebased training (with elastic bands) was compared with solely home-based training, over 1 year. At follow-up every third month, duplicated six minute walk test (6MWT) and two HRQoL questionnaires were used. The walking distance increased significantly after three months in both groups and was maintained thereafter. Also HRQoL increased but at different time points. In study II, PMT was compared with interval training on an ergometer bike/free walking. Both groups started under supervision of a physiotherapist in a hospital-setting, for three months and thereafter at home for nine months. The same measurements were used as in study I. Neither walking distance nor HRQoL changed over the study period. However, this may be regarded as a positive effect in the light of the known progressive nature of heart failure. In study III, the 6MWTs from study I and II were used to evaluate the necessity of performing duplicated 6MWTs in follow-ups clinically and for research purposes. We found that it is sufficient to perform one 6MWT. In study IV, both 6MWT and HRQoL forms from study I and II were used to investigate the relationship between walking distance and perceived HRQoL in HF patients. Patients with shorter walking distance, than the group median, experienced poorer general HRQoL but not HRQoL related to HF, than the higher performing half of the study group. There were no longitudinal trends in these relationships.Conclusion: PMT can be used as an exercise modality in patients with HF, both in hospital and at home, and may be evaluated with a single 6MWT. Shorter walking distance was related to a lower general HRQoL as judged by the patients but there was no significant relation between short walking distance and the HF-related HRQoL. Individualizing the training programme and methods, and offering the choice of exercise modality and the possibility of exercising at home, might be a way to increase adherence in cardiac rehabilitation.
|
|
| 6. |
- Maret, Eva, 1961-
(författare)
-
Noninvasive Evaluation of Myocardial Ischemia and Left Ventricular Function
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The general aim of this thesis was, following the path of the ischemic cascade, to evaluate the feasibility of some new non-invasive techniques for the detection of myocardial ischemia, the extent of infarcted myocardium, and for the quantification of systolic left ventricular function.Reduced longitudinal myocardial velocity and displacement may be early signs of ischemia. We evaluated the diagnostic sensitivity and specificity of pulsed tissue Doppler for the detection of ischemia and scar during dobutamine stress testing and compared it with myocardial perfusion scintigraphy (SPECT) in patients with a history of unstable angina. Pulsed tissue Doppler was useful for objective quantification of left ventricular longitudinal shortening and for differentiation between patients with a normal, ischemic or necrotic myocardium.The coronary flow velocity reserve (CFVR) of the left anterior descending artery (LAD) was studied with transthoracic Doppler echocardiography (TTDE) during adenosine stress. Patients with a clinical suspicion of stress induced myocardial ischemia were investigated, and the results were compared with the findings from SPECT. A CFVR >2 in the LAD could exclude significant coronary artery disease in a clinical setting, however, in cases with low CFVR, multiple cardiovascular and metabolic risk factors as well as epicardial coronary artery disease or microvascular dysfunction might be responsible. TTDE is a promising tool, e.g. for follow-up after coronary interventions or for evaluating endothelial function over time.A third study focused on the importance of accurate and reproducible measurements of left ventricular volumes and ejection fraction (LVEF). Patients with known or suspected coronary artery disease with different levels of LVEF were enrolled. We compared the LVEF determined with an automatic echocardiographic method with manual planimetry, visual assessment of LVEF and with quantitative myocardial gated SPECT. The software using learned pattern recognition and artificial intelligence (AutoEF) applied on biplane apical echocardiographic views reduced the variation in measurements without increasing the time required. The method seems to be able to reduce variation in the assessment of LVEF in clinical patients, especially for less experienced readers.We evaluated a new feature tracking software for its ability to detect infarcted myocardium on cine-MR images. Patients were selected based on the presence or absence of myocardial scar in the perfusion area of the LAD. The software tracked myocardial wall motion and allowed the calculation of velocity, displacement and strain in radial and longitudinal directions. Feature tracking of cine-MR images detected scar segments with transmurality >50% within the distribution of the LAD with 80% sensitivity and 86% specificity (radial strain), without the need for the administration of gadolinium-based contrast.In summary, we have evaluated some of the noninvasive techniques in the wide array of diagnostic tools available for the diagnosis of ischemic heart disease. Their availability, low costs, freedom from radiation and repeatability are essential as well as their diagnostic ability.
|
|
| 7. |
- Nilsson, Staffan, 1955-
(författare)
-
Chest pain and ischemic heart disease : Diagnosis and management in primary health care
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background and aims. In patients consulting for chest pain, it is of great importance to evaluate the possibility of ischemic heart disease (IHD). The aims in this thesis were to investigate the accuracy of the general practitioners’ clinical assessments and the applicability of exercise testing and myocardial perfusion scintigraphy (MPS) in patients consulting for chest pain in primary care.Statins are known to prevent IHD. A further aim was therefore to investigate if a relation could be detected on a population basis between the use of statins and the morbidity of acute myocardial infarction (AMI).Methods. All patients from 20 to 79 years, consulting for a new episode of chest pain in three primary health care centres, were included during almost two years from 1998 to 2000. The patients were managed according to the clinical evaluation. The presence of IHD was excluded either by clinical examination only, or if stable IHD was in question, by exercise testing and if the exercise test was inconclusive by an additional MPS. If unstable IHD or myocardial infarction was suspected, referral for emergency hospital examination was made.Correlations between statin sales and the morbidity of AMI in Sweden’s municipalities were analysed in an ecological, register based study. Adjustment was made for sales of antidiabetics, socio-economic deprivation indexes and geographic coordinates.Results. Consultations for chest pain represented 1.5% of all consultations in the ages 20 to 79 and were made by 554 patients. In 281 patients IHD was excluded by clinical examination only. In 208 patients stable IHD and in 65 unstable IHD was in question. Four patients (1.4%) evaluated as not having IHD, were diagnosed with angina pectoris or AMI within three months. Exercise testing was performed in 191 patients and revealed no IHD in 134 and IHD in 14 patients. In 43 patients the exercise test results were equivocal. Thirty-nine of these patients underwent MPS, which showed no IHD in 20 and IHD in 19 of the patients.In a follow up almost six years later, neither mortality rate nor prevalence of IHD differed significantly between the 384 study patients evaluated not to have IHD and the population controls.Statin sales and AMI-incidence or mortality showed no strong associations from 1998 to 2002.Conclusions.·Primary care is an appropriate level of care for ruling out IHD as the cause of chest pain, with sufficient safety and for diagnostics of stable IHD.·Exercise testing and myocardial perfusion scintigraphy are useful procedures when investigating chest pain patients in primary care.·The results indicate that preventive measures other than increased statin treatment should be considered to further decrease AMI-morbidity.
|
|
| 8. |
- Tamás, Éva, 1968-
(författare)
-
Surgical treatment in chronic aortic regurgitation : Timing, results, prognosis and left ventricular function
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chronic aortic regurgitation (AR) of varying degree affects 13% of men and 8.5% of women. In persons with severe AR, the expected length of life and its quality are influenced. Some individuals remain asymptomatic for a long period, due to effective compensatory mechanisms, but dysfunction of the left ventricle (LV) usually begins before symptoms appear and can be irreversible by then. This thesis addresses questions of LV function and optimal time for operation of patients suffering from chronic AR. Moreover, detailed echocardiographic studies of the anatomy of the normal aortic valve have been performed to obtain a better understanding of the in vivo anatomic relations within the aortic root.Patients with chronic AR, without concomitant cardiac disease, were studied both retrospectively (n=88) and prospectively (n=29) and the aortic valves of persons (n=32) free from cardiac disease were investigated.For the retrospectively studied patients, survival was 82% at 10 years which is an improvement compared with previously published results. The majority of the patients, however, had LV dysfunction preoperatively. By studying patients prospectively by echocardiography, radionuclide ventriculography (MUGA) and cardiopulmonary exercise testing (CPET) our aim was to evaluate the predictive value of measurements of LV function at rest and during exercise for postoperative outcome. LV diameters were markedly elevated prior to and diminished significantly after surgery. Patients with an abnormal exercise ejection fraction (EF) response by MUGA preoperatively, presented the same reaction postoperatively. This could not be predicted by LV function determination at rest, or by NYHA functional class. In spite of median NYHA class II, these patients had a low work capacity on CPET, which was neither improved 6 months postoperatively nor correlated to echocardiographic LV dimensions. Thus, both MUGA and CPET may be useful complements for timing of surgery in patients with chronic AR.Assuming that patients would benefit from preservation of their native valves the normal aortic valve was studied to gain detailed information about the echocardiographic anatomy and relations within the normal aortic root. This extended examination of the aortic root may facilitate a better planning of aortic valve‐preserving interventions in the future.
|
|
| 9. |
- Åström Aneq, Meriam
(författare)
-
Arrhythmogenic right ventricular cardiomyopathy : Is it right?
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart disease, where sudden cardiac death in young seemingly healthy persons may be the first symptom. There is a need for more sensitive and accurate diagnostic methods to detect signs of disease, at an early stage and in relatives of affected individuals. The aim of this thesis is the evaluation of new non-invasive modalities in assessment of right ventricular (RV) volume and function with focus on patients with ARVC.Clinical and non-invasive follow-up of fifteen patients with ARVC during a mean period of 8 years permitted the evaluation of disease progression. RV volume analysis by magnetic resonance imaging relies on short axis (SA) views. A new axially rotated modality acquisition was tested and its feasibility in assessment of RV volume was evaluated. This acquisition seems to be able to improve the assessment of RV volume and function by reducing the uncertainty in defining the basal slice of the RV. A third study concentrated on analysis of RV regional and general function by echocardiography, using tissue Doppler imaging as well as two dimensional (2D) longitudinal strain based on speckle tracking in patients with ARVC, their first degree relatives and in healthy subjects. 2D strain showed a good feasibility in analysis of the RV function in relatives and controls but less in ARVC patients probably due to the progressive myocardial cell death with fibro-fatty replacement of the RV wall. In order to detect and follow up echocardiographic changes an index was developed combining dimensional and functional parameters for the left and for the right ventricle. Advances in the molecular genetics of ARVC have provided new insights into the understanding of the disease. Hitherto, 9 candidate genes have been identified. A new mutation in the plakophilin 2 gene was detected in a three generation family. The clinical phenotype related to this mutation was investigated.The studies have evaluated and developed methods for studying the right ventricle with special emphasis on ARVC. With the ultimate goal of preventing sudden death in ARVC, a combination of genetic testing and improved diagnostic methods may create an improved algorithm for risk stratification and selection to prophylactic treatment.
|
|
