| 1. |
- Bergfeldt, Lennart, 1950, et al.
(författare)
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Spatial peak and mean QRS-T angles: A comparison of similar but different emerging risk factors for cardiac death.
- 2020
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Ingår i: Journal of electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 61, s. 112-120
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Tidskriftsartikel (refereegranskat)abstract
- The spatial peak and mean QRS-T angles are scientifically but not clinically established risk factors for cardiovascular events including cardiac death. The study aims were to compare these angles, assess their association with hypertension (HT) and diabetes mellitus (DM), and explore the relation between the mean QRS-T angle and the ventricular gradient (VG; reflecting electrical heterogeneity), which both are derived from the QRSarea and Tarea vectors.Altogether 1094 participants (aged 50-65years, 550 women) from the pilot of the population-based Swedish CArdioPulmonary bioImage Study with Frank vectorcardiographic recordings were included and divided into 5 subgroups: apparently healthy n=320; HT n=311; DM n=33; DM+HT n=53; miscellaneous conditions n=377. Abnormal peak and mean QRS-T angles were defined as >95th percentile.Peak QRS-T angles were generally narrower than the mean QRS-T angles; both were narrower in women than in men. Abnormal peak (>124°) and/or mean (>119°) QRS-T angles were found in 73 participants (6.7%). The concordance regarding abnormal versus normal-borderline QRS-T angles was good (Cohen's kappa 0.61). The prevalence of abnormal angles varied from 2.5% in healthy to 21.2% in DM. There was an inverse logarithmical relation between the mean QRS-T angle and the VG.The peak and mean QRS-T angles are not interchangeable but complementary. DM, HT, sex and absence of disease are important determinants of both QRS-T angles. The mean QRS-T angle and the VG relationship is complex. All three VCG derived measures reflect related but differing electrophysiological properties and have potential prognostic value vis-à-vis cardiovascular events.
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| 2. |
- Bergfeldt, Lennart, 1950, et al.
(författare)
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Ventricular repolarization duration and dispersion adaptation after atropine induced rapid heart rate increase in healthy adults.
- 2017
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Ingår i: Journal of electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 50:4, s. 424-432
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Tidskriftsartikel (refereegranskat)abstract
- Proper adaptation of ventricular repolarization (VR) to rapid heart rate (HR) increase is crucial for cardiac electro-mechanical function. The pattern and temporal aspects of this adaptation and its components (duration and dispersion) during normal conduction are, however, incompletely known in humans and were the topic of this study.The VR duration (QT & QTpeak) and dispersion (Tamplitude, Tarea & ventricular gradient; VG) responses were studied by continuous vectorcardiogram after a bolus injection of atropine 0.04mg/kg b.w. in 31 healthy young adults (16 men). The primary measure (T90 End) was the time to reach 90% change from baseline to end value 300s later. Mean (SD) of T90 End was 23 (9) s for a 41% RR decrease, 130 (35) s for a 16% QTend decrease and 110 (36) s for a 19% QTpeak decrease; the response was single-exponential for these measures. For 35-43% decreases of Tamplitude, Tarea & VG, mean (SD) of T90 End were 21 (10), 38 (20) and 40 (23) s and the response pattern was double-exponential with varying overshoot.VR duration and dispersion responses to a very rapid HR increase during normal conduction differed substantially. In contrast to the well-known single-exponential delay in VR duration adaptation the responses of VR dispersion measures were double-exponential and much more rapid. We describe a new and completely non-invasive phenotypic characterization of different components of VR adaptation.
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| 3. |
- Lundahl, Gunilla, et al.
(författare)
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Automatic identification of a stable QRST complex for non-invasive evaluation of human cardiac electrophysiology.
- 2020
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 15:9
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Tidskriftsartikel (refereegranskat)abstract
- A vectorcardiography approach to electrocardiology contributes to the non-invasive assessment of electrical heterogeneity in the ventricles of the heart and to risk stratification for cardiac events including sudden cardiac death. The aim of this study was to develop an automatic method that identifies a representative QRST complex (QRSonset to Tend) from a Frank vectorcardiogram (VCG). This method should provide reliable measurements of morphological VCG parameters and signal when such measurements required manual scrutiny.Frank VCG was recorded in a population-based sample of 1094 participants (550 women) 50-65 years old as part of the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot. Standardized supine rest allowing heart rate stabilization and adaptation of ventricular repolarization preceded a recording period lasting ≥5 minutes. In the Frank VCG a recording segment during steady-state conditions and with good signal quality was selected based on QRST variability. In this segment a representative signal-averaged QRST complex from cardiac cycles during 10s was selected. Twenty-eight morphological parameters were calculated including both conventional conduction intervals and VCG-derived parameters. The reliability and reproducibility of these parameters were evaluated when using completely automatic and automatic but manually edited annotation points.In 1080 participants (98.7%) our automatic method reliably selected a representative QRST complex where its instability measure effectively identified signal variability due to both external disturbances ("noise") and physiologic and pathophysiologic variability, such as e.g. sinus arrhythmia and atrial fibrillation. There were significant sex-related differences in 24 of 28 VCG parameters. Some VCG parameters were insensitive to the instability value, while others were moderately sensitive.We developed an automatic process for identification of a signal-averaged QRST complex suitable for morphologic measurements which worked reliably in 99% of participants. This process is applicable for all non-invasive analyses of cardiac electrophysiology including risk stratification for cardiac death based on such measurements.
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| 4. |
- Nygren, Martin, et al.
(författare)
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Identification of 2,3,7,8-substituted polychlorinated dioxins and dibenzofurans in environmental and human samples
- 1986. - 1
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Ingår i: Chlorinated dioxins and dibenzofurans in perspective. - Boca Raton : CRC Press. - 9781315891545 - 9781351070645 ; , s. 17-34
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are two series of tricyclic, almost planar aromatic compounds that exhibit very similar physical, chemical, and biological properties. The human exposure to PCDDs and PCDFs by milk consumption is not negligible. Detection levels in ecological and human samples should be orders of magnitude below the usual detection levels obtained in pesticide analyses. One objective of the study is to identify background levels of PCDDs and PCDFs in these samples, especially those of human origin. The spectrum of toxic effects is species dependent but for humans they include chloracne and porphyria cutane tarda and for other animals edema, thymic atrophy, teratogenicity, liver lesions and a slow wasting syndrome followed by death. It is evident that it is of particular importance to identify the ultimate source or sources of the toxic 2,3,7,8-substituted PCDDs and PCDFs found as background constituents in the environmental and human samples, especially the samples of mother's milk, which are of toxicological interest.
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| 5. |
- Vahedi, Farzad, et al.
(författare)
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Instability of repolarization in LQTS mutation carriers compared to healthy control subjects assessed by vectorcardiography
- 2013
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Ingår i: Heart Rhythm. - : Elsevier BV. - 1547-5271 .- 1556-3871. ; 10:8, s. 1169-1175
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND Potassium channel dysfunction in congenital and acquired forms of long QT syndrome types 1 and 2 (LQT1 and LQT2) increases the beat-to-beat variability of the (IT interval. OBJECTIVE To study about the little known variability (instability) of other aspects of ventricular repolarization (VR) in humans by using vectorcardiography. METHODS Beat-to-beat analysis was performed regarding vectorcardiography derived RR, QRS, and QT intervals, as well as T vector- and T vector loop-based parameters during 1-minute recordings of uninterrupted sinus rhythm at rest in 41 adult LQT1 (n = 31) and LQT2 (n = 10) mutation carriers and 41 age- and sex-matched control subjects. The short-term variability for each parameter, describing the mean orthogonal distance to the line of identity on the Poincare plot, was calculated. RESULTS Mutation carriers showed significantly larger (by a factor 2) instability in most VR parameters compared to controls despite higher instantaneous heart rate variability (STVRR) in the control group. The longer the (IT interval, the greater was its instability, and the instability of VR dispersion measures. CONCLUSIONS A greater instability of most aspects of VR already at rest seems to be a salient feature in both LQT1 and LQT2, which might pave the way for early afterdepolarizations and torsades de pointes ventricular tachycardia. In contrast, no signs of increased VR dispersion per se were observed in mutation carriers.
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| 6. |
- Bergqvist, Lennart, et al.
(författare)
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Particle sizing and biokinetics of interstitiallymphoscintigraphic agents
- 1983
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Ingår i: Seminars in Nuclear Medicine. - 0001-2998. ; 13:1, s. 9-19
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Tidskriftsartikel (refereegranskat)abstract
- The biokinetics of inert lymphoscintigraphic agentsstrongly depends on their particle size. Different techniques for characterization of colloids are discussed. Experiments have been performed on eight different colloids. The particle size has been investigated with scanning electron microscopy. Activity distributions have been obtained with ultrafiltration and gel-column scanning technique. The colloids suggested for lymphoscintigraphy were found to have a median size of about 40-50 nm except one minimicro-aggregated human serum albumin colloid which has a median particle size around 10 nm. The biokinetics were studied with a scintillation camera in rabbits after a subcutaneous injection. Timeactivity curves were generated. After 5 hr the rabbits were dissected and the activity content in different tissues measured. A compartment model for the biokinetics was designed and rate constants evaluated. The total and specific activity uptake in parasternal lymph nodes was highest for the small-particle colloids. The compartment model showed a good fitting to the experimental data.
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| 7. |
- Christiansson, Lennart, et al.
(författare)
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A new method of intrathecal PO2, PCO2, and pH measurements for continuous monitoring of spinal cord ischemia during thoracic aortic clamping in pigs
- 2000
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Ingår i: Surgery. - : Elsevier BV. - 0039-6060 .- 1532-7361. ; 127:5, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Impaired spinal cord circulation during thoracic aortic clamping may result in paraplegia. Reliable and fast responding methods for intraoperative monitoring are needed to facilitate the evaluation of protective measures and efficiency of revascularization.METHODS: In 11 pigs, a multiparameter PO2, PCO2, and pH sensor (Paratrend 7, Biomedical Sensors Ltd, United Kingdom) was introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenation during thoracic aortic cross-clamping (AXC) distal to the left subclavian artery. A laser-Doppler probe was inserted into the epidural space for simultaneous measurements of spinal cord flux. Registrations were made before and 30 minutes after clamping and 30 and 60 minutes after declamping. The same measuring points were used for systemic hemodynamic and metabolic data acquisition.RESULTS: The mean CSF PO2 readings of 41 mm Hg (5.5 kPa) at baseline decreased within 3 minutes to 5 mm Hg (0.7 kPa) during AXC (P < .01). Spinal cord flux measurement responded immediately in the same way to AXC. Both methods indicated normalization of circulation during declamping. Significant (P < .01) changes were also observed in the CSF metabolic parameters PCO2 and pH.CONCLUSIONS: In this experimental model of spinal ischemia by AXC, online monitoring of intrathecal PO2, PCO2, and pH showed significant changes and correlated well with epidural laser-Doppler flowmetry (P < .01).
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| 8. |
- Christiansson, Lennart, et al.
(författare)
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Aspects of the spinal cord circulation as assessed by intrathecal oxygen tension monitoring during various arterial interruptions in the pig
- 2001
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Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier BV. - 0022-5223 .- 1097-685X. ; 121:4, s. 762-772
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: We sought to study the effect of various modes of interruption of the spinal cord blood supply on intrathecal oxygenation.METHODS: In 24 pigs intrathecal PO (2), PCO (2), and pH were continuously monitored with a multiparameter catheter (Paratrend 7, Biomedical Sensors; Diametrics Medical, Inc, St Paul, Minn) during and after aortic crossclamping or selective interruption of segmental arteries and proximal collateral circulation.RESULTS: Proximal aortic clamping (n = 6) produced complete ischemia, whereas a second clamp close to the celiac trunk (n = 4) partly protected against spinal cord ischemia. This is explained by prevention of the steal phenomenon in the excluded part of the aorta. Adding clamps to the subclavian arteries (n = 6) created complete spinal ischemia as the collateral circulation was interrupted. In another group (n = 4) all segmental arteries below T5 were occluded with no reaction in the intrathecal variables. Additional selective clamping of supreme intercostal arteries (n = 4) showed the relative importance of the subclavian and vertebral collateral pathways.CONCLUSIONS: Continuous intrathecal PO (2) was monitored during various modes of interruption of the spinal cord blood supply. This provided insight into the ischemia mechanisms and relative importance of the segmental contribution and proximal collateral pathways of the spinal cord circulation in pigs. A short literature review is given, and aspects of comparative anatomy are discussed.
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| 9. |
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| 10. |
- Christiansson, Lennart, et al.
(författare)
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Increased FiO2 improves intrathecal oxygenation during thoracic aortic cross-clamping in pigs
- 2001
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Ingår i: Scandinavian Cardiovascular Journal. - 1401-7431 .- 1651-2006. ; 35:2, s. 147-150
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate the effect of 100% oxygen ventilation on cerebrospinal fluid (CSF) oxygenation in 11 pigs during thoracic aortic cross-clamping.DESIGN: An aorto-aortic shunt was used for control of central hemodynamics and study of hypoperfusion by exsanguination. CSF PO2, PCO2 and pH were continuously monitored before and during clamping. The changes in hemodynamic parameters and intrathecal gas tensions in response to variations in proximal mean aortic pressure and fraction of inspired oxygen (FiO2) were recorded.RESULTS: Baseline CSF PO2 decreased from 4.8 +/- 1.9 to 2.6 +/- 2.2 kPa following aortic occlusion. Increasing FiO2 to 1.0 resulted in a significant increase in CSF PO2 to 4.1 +/- 3.0 with a return to 2.7 +/- 2.1 kPa after reducing FiO2 to 0.4 again. The same variations in FiO2 did not induce any significant changes in CSF PO2 during hypotension.CONCLUSION: Increased FiO2 during experimental thoracic aortic cross-clamping with stable proximal arterial pressure helps to maintain CSF PO2, whereas severe hypotension could not be compensated for by hyperoxemia.
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