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Dahlberg P, Axelsson KJ, Rydberg A, Lundahl G, Gransberg L, Bergfeldt L. Spatiotemporal repolarization dispersion before and after exercise in patients with long QT syndrome type 1 versus controls: probing into the arrhythmia substrate. Am J Physiol Heart Circ Physiol 2023; 325:H1279-H1289. [PMID: 37773058 DOI: 10.1152/ajpheart.00335.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 09/21/2023] [Accepted: 09/22/2023] [Indexed: 09/30/2023]
Abstract
Congenital long QT syndrome (LQTS) carries an increased risk for syncope and sudden death. QT prolongation promotes ventricular extrasystoles, which, in the presence of an arrhythmia substrate, might trigger ventricular tachycardia degenerating into fibrillation. Increased electrical heterogeneity (dispersion) is the suggested arrhythmia substrate in LQTS. In the most common subtype LQT1, physical exercise predisposes for arrhythmia and spatiotemporal dispersion was therefore studied in this context. Thirty-seven patients (57% on β-blockers) and 37 healthy controls (mean age, 31 vs. 35; range, 6-68 vs. 6-72 yr) performed an exercise test. Frank vectorcardiography was used to assess spatiotemporal dispersion as Tampl, Tarea, the ventricular gradient (VG), and the Tpeak-end interval from 10-s signal averages before and 7 ± 2 min after exercise; during exercise too much signal disturbance excluded analysis. Baseline and maximum heart rates as well as estimated exercise intensity were similar, but heart rate recovery was slower in patients. At baseline, QT and heart rate-corrected QT (QTcB) were significantly longer in patients (as expected), whereas dispersion parameters were numerically larger in controls. After exercise, QTpeakcB and Tpeak-endcB increased significantly more in patients (18 ± 23 vs. 7 ± 10 ms and 12 ± 17 vs. 2 ± 6 ms; P < 0.001 and P < 0.01). There was, however, no difference in the change in Tampl, Tarea, and VG between groups. In conclusion, although temporal dispersion of repolarization increased significantly more after exercise in patients with LQT1, there were no signs of exercise-induced increase in global dispersion of action potential duration and morphology. The arrhythmia substrate/mechanism in LQT1 warrants further study.NEW & NOTEWORTHY Physical activity increases the risk for life-threatening arrhythmias in LQTS type 1 (LQT1). The arrhythmia substrate is presumably altered electrical heterogeneity (a.k.a. dispersion). Spatiotemporal dispersion parameters were therefore compared before and after exercise in patients versus healthy controls using Frank vectorcardiography, a novelty. Physical exercise prolonged the time between the earliest and latest complete repolarization in patients versus controls, but did not increase parameters reflecting global dispersion of action potential duration and morphology, another novelty.
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Affiliation(s)
- Pia Dahlberg
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Region Vaestra Goetaland, Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Karl-Jonas Axelsson
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Region Vaestra Goetaland, Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Annika Rydberg
- Division of Pediatrics, Department of Clinical Sciences, Umeå University, Umeå, Sweden
| | - Gunilla Lundahl
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lennart Gransberg
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lennart Bergfeldt
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Region Vaestra Goetaland, Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
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Stabenau HF, Sau A, Kramer DB, Peters NS, Ng FS, Waks JW. Limits of the spatial ventricular gradient and QRST angles in patients with normal electrocardiograms and no known cardiovascular disease stratified by age, sex, and race. J Cardiovasc Electrophysiol 2023; 34:2305-2315. [PMID: 37681403 DOI: 10.1111/jce.16062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 08/20/2023] [Accepted: 08/28/2023] [Indexed: 09/09/2023]
Abstract
INTRODUCTION Measurement of the spatial ventricular gradient (SVG), spatial QRST angles, and other vectorcardiographic measures of myocardial electrical heterogeneity have emerged as novel risk stratification methods for sudden cardiac death and other adverse cardiovascular events. Prior studies of normal limits of these measurements included primarily young, healthy, White volunteers, but normal limits in older patients are unknown. The influence of race and body mass index (BMI) on these measurements is also unclear. METHODS Normal 12-lead electrocardiograms (ECGs) from a single center were identified. Patients with abnormal cardiovascular, pulmonary, or renal history (assessed by International Classification of Disease [ICD-9/ICD-10] codes) or abnormal cardiovascular imaging were excluded. The SVG and QRST angles were measured and stratified by age, sex, and race. Multivariable linear regression was used to assess the influence of age, BMI, and heart rate (HR) on these measurements. RESULTS Among 3292 patients, observed ranges of SVG and QRST angles (peak and mean) differed significantly based on sex, age, and race. Sex differences attenuated with increasing age. Men tended to have larger SVG magnitude (60.4 [46.1-77.8] vs. 52.5 [41.3-65.8] mv*ms, p < .0001) and elevation, and more anterior/negative SVG azimuth (-14.8 [-25.1 to -4.3] vs. 1.3 [-9.8 to 10.5] deg, p < .0001) compared to women. Men also had wider QRST angles. Observed ranges varied significantly with BMI and HR. SVG and QRST angle measurements were robust to different filtering bandwidths and moderate fiducial point annotation errors, but were heavily affected by changes in baseline correction. CONCLUSIONS Age, sex, race, BMI, and HR significantly affect the range of SVG and QRST angles in patients with normal ECGs and no known cardiovascular disease, and should be accounted for in future studies. An online calculator for prediction of these "normal limits" given demographics is provided at https://bivectors.github.io/gehcalc/.
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Affiliation(s)
- Hans F Stabenau
- Division of Electrophysiology, Harvard Medical School, Beth Israel Deaconess Medical Center, Harvard-Thorndike Arrhythmia Institute, Boston, Massachusetts, USA
| | - Arunashis Sau
- National Heart and Lung Institute, Imperial College London, London, UK
- Department of Cardiology, Imperial College Healthcare NHS Trust, London, UK
| | - Daniel B Kramer
- Division of Electrophysiology, Harvard Medical School, Beth Israel Deaconess Medical Center, Harvard-Thorndike Arrhythmia Institute, Boston, Massachusetts, USA
- National Heart and Lung Institute, Imperial College London, London, UK
- Harvard Medical School, Smith Center for Outcomes Research, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Nicholas S Peters
- National Heart and Lung Institute, Imperial College London, London, UK
- Department of Cardiology, Imperial College Healthcare NHS Trust, London, UK
| | - Fu Siong Ng
- National Heart and Lung Institute, Imperial College London, London, UK
- Department of Cardiology, Imperial College Healthcare NHS Trust, London, UK
| | - Jonathan W Waks
- Division of Electrophysiology, Harvard Medical School, Beth Israel Deaconess Medical Center, Harvard-Thorndike Arrhythmia Institute, Boston, Massachusetts, USA
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Dahlberg P, Axelsson K, Jensen SM, Lundahl G, Vahedi F, Perkins R, Gransberg L, Bergfeldt L. Accelerated QT adaptation following atropine-induced heart rate increase in LQT1 patients versus healthy controls: A sign of disturbed hysteresis. Physiol Rep 2022; 10:e15487. [PMID: 36324292 PMCID: PMC9630760 DOI: 10.14814/phy2.15487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 09/08/2022] [Accepted: 09/19/2022] [Indexed: 06/16/2023] Open
Abstract
Hysteresis, a ubiquitous regulatory phenomenon, is a salient feature of the adaptation of ventricular repolarization duration to heart rate (HR) change. We therefore compared the QT interval adaptation to rapid HR increase in patients with the long QT syndrome type 1 (LQT1) versus healthy controls because LQT1 is caused by loss-of-function mutations affecting the repolarizing potassium channel current IKs , presumably an important player in QT hysteresis. The study was performed in an outpatient hospital setting. HR was increased in LQT1 patients and controls by administering an intravenous bolus of atropine (0.04 mg/kg body weight) for 30 s. RR and QT intervals were recorded by continuous Frank vectorcardiography. Atropine induced transient expected side effects but no adverse arrhythmias. There was no difference in HR response (RR intervals) to atropine between the groups. Although atropine-induced ΔQT was 48% greater in 18 LQT1 patients than in 28 controls (p < 0.001), QT adaptation was on average 25% faster in LQT1 patients (measured as the time constant τ for the mono-exponential function and the time for 90% of ΔQT; p < 0.01); however, there was some overlap between the groups, possibly a beta-blocker effect. The shorter QT adaptation time to atropine-induced HR increase in LQT1 patients on the group level corroborates the importance of IKs in QT adaptation hysteresis in humans and shows that LQT1 patients have a disturbed ultra-rapid cardiac memory. On the individual level, the QT adaptation time possibly reflects the effect-size of the loss-of-function mutation, but its clinical implications need to be shown.
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Affiliation(s)
- Pia Dahlberg
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Karl‐Jonas Axelsson
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Steen M. Jensen
- Department of Public Health and Clinical Medicine, and Heart CentreUmeå UniversityUmeåSweden
| | - Gunilla Lundahl
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Farzad Vahedi
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
| | - Rosie Perkins
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Lennart Gransberg
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Lennart Bergfeldt
- Department of Molecular and Clinical MedicineInstitute of Medicine, Sahlgrenska Academy, University of GothenburgGothenburgSweden
- Region Västra Götaland, Department of CardiologySahlgrenska University HospitalGothenburgSweden
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Lundahl G, Gransberg L, Bergqvist G, Bergström G, Bergfeldt L. Automatic identification of a stable QRST complex for non-invasive evaluation of human cardiac electrophysiology. PLoS One 2020; 15:e0239074. [PMID: 32941513 PMCID: PMC7498068 DOI: 10.1371/journal.pone.0239074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 08/28/2020] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND 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. METHODS 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. RESULTS 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. CONCLUSION 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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Affiliation(s)
- Gunilla Lundahl
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lennart Gransberg
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Gabriel Bergqvist
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Göran Bergström
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Clinical Physiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Lennart Bergfeldt
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
- * E-mail:
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5
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Gemmell PM, Gillette K, Balaban G, Rajani R, Vigmond EJ, Plank G, Bishop MJ. A computational investigation into rate-dependant vectorcardiogram changes due to specific fibrosis patterns in non-ischæmic dilated cardiomyopathy. Comput Biol Med 2020; 123:103895. [PMID: 32741753 PMCID: PMC7429989 DOI: 10.1016/j.compbiomed.2020.103895] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 06/12/2020] [Accepted: 06/27/2020] [Indexed: 01/13/2023]
Abstract
Patients with scar-associated fibrotic tissue remodelling are at greater risk of ventricular arrhythmic events, but current methods to detect the presence of such remodelling require invasive procedures. We present here a potential method to detect the presence, location and dimensions of scar using pacing-dependent changes in the vectorcardiogram (VCG). Using a clinically-derived whole-torso computational model, simulations were conducted at both slow and rapid pacing for a variety of scar patterns within the myocardium, with various VCG-derived metrics being calculated, with changes in these metrics being assessed for their ability to discern the presence and size of scar. Our results indicate that differences in the dipole angle at the end of the QRS complex and differences in the QRS area and duration may be used to predict scar properties. Using machine learning techniques, we were also able to predict the location of the scar to high accuracy, using only these VCG-derived rate-dependent changes as input. Such a non-invasive predictive tool for the presence of scar represents a potentially useful clinical tool for identifying patients at arrhythmic risk.
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Affiliation(s)
- Philip M Gemmell
- King's College London, St. Thomas' Hospital North Wing, London, SE1 7EH, UK.
| | - Karli Gillette
- Medical University of Graz, Division of Biophysics, Neue Stiftingtalstraße 6(MC1.D.)/IV, 8010 Graz, Austria
| | - Gabriel Balaban
- University of Oslo, Research Group for Biomedical Infomatics, Gaustadalléen 23B 0373 Oslo, Norway
| | - Ronak Rajani
- King's College London, St. Thomas' Hospital North Wing, London, SE1 7EH, UK
| | - Edward J Vigmond
- University of Bordeaux, IHU Liryc, Site Hopital Xavier Arnozan, Avenue de Haut-Leveque, 33604 Pessac, France
| | - Gernot Plank
- Medical University of Graz, Division of Biophysics, Neue Stiftingtalstraße 6(MC1.D.)/IV, 8010 Graz, Austria
| | - Martin J Bishop
- King's College London, St. Thomas' Hospital North Wing, London, SE1 7EH, UK
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Bergfeldt L, Lundahl G, Bergqvist G, Vahedi F, Gransberg L. Ventricular repolarization duration and dispersion adaptation after atropine induced rapid heart rate increase in healthy adults. J Electrocardiol 2017; 50:424-432. [DOI: 10.1016/j.jelectrocard.2017.03.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Indexed: 11/16/2022]
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7
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Dilaveris P, Antoniou CK, Gatzoulis K, Tousoulis D. T wave axis deviation and QRS-T angle - Controversial indicators of incident coronary heart events. J Electrocardiol 2017; 50:466-475. [PMID: 28262257 DOI: 10.1016/j.jelectrocard.2017.02.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Indexed: 11/29/2022]
Abstract
Abnormal orientation of the T-wave axis and increased angle between the QRS complex (depolarization) and the T-wave (repolarization) have long been assumed to provide a global measure of repolarization abnormality, and have been used to assess ventricular repolarization. The ability of the T wave axis deviation and the QRS-T angle to predict incident coronary heart events was examined in several studies. However, conflicting results have led to significant controversy in the literature concerning their purported ability. Potential explanations involve true variation between study populations, non-standardized cut-off values, different baseline cardiovascular risk levels or different patterns of confounding by other concomitant cardiovascular risk factors. In the present article we will attempt to briefly present the rationale and pathophysiology behind these indices, summarize existing knowledge regarding their prognostic significance and their correlation with established cardiovascular disease risk factors. Further prospective studies are necessary to confirm or refute whether T-wave axis deviation, QRS-T angle and ventricular gradient may in the future serve as indicators of incident coronary heart events and mortality, both in populations with higher prevalence of subclinical advanced atherosclerotic heart disease and in apparently healthy subjects.
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Affiliation(s)
- Polychronis Dilaveris
- First Department of Cardiology, University of Athens Medical School, Hippokration Hospital, Athens, Greece.
| | | | - Konstantinos Gatzoulis
- First Department of Cardiology, University of Athens Medical School, Hippokration Hospital, Athens, Greece
| | - Dimitrios Tousoulis
- First Department of Cardiology, University of Athens Medical School, Hippokration Hospital, Athens, Greece
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8
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Waks JW, Tereshchenko LG. Global electrical heterogeneity: A review of the spatial ventricular gradient. J Electrocardiol 2016; 49:824-830. [PMID: 27539162 DOI: 10.1016/j.jelectrocard.2016.07.025] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Indexed: 11/18/2022]
Abstract
The ventricular gradient, an electrocardiographic concept calculated by integrating the area under the QRS complex and T-wave, represents the degree and direction of myocardial electrical heterogeneity. Although the concept of the ventricular gradient was first introduced in the 1930s, it has not yet found a place in routine electrocardiography. In the modern era, it is relatively simple to calculate the ventricular gradient in three dimensions (the spatial ventricular gradient (SVG)), and there is now renewed interest in using the SVG as a tool for risk stratification of ventricular arrhythmias and sudden cardiac death. This manuscript will review the history of the ventricular gradient, describe its electrophysiological meaning and significance, and discuss its clinical utility.
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Affiliation(s)
- Jonathan W Waks
- Division of Cardiovascular Medicine, Harvard-Thorndike Electrophysiology Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
| | - Larisa G Tereshchenko
- Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA
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9
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Poulikakos D, Banerjee D, Malik M. Repolarisation descriptors and heart rate variability in hemodialysed patients. Physiol Res 2014; 64:487-93. [PMID: 25470516 DOI: 10.33549/physiolres.932740] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
T wave morphology (TWM) descriptors derived from Holter electrocardiograms during hemodialysis (HD) are of potential value for cardiac risk assessment in HD patients. Our knowledge on autonomic regulation of TWM descriptors is limited. The purpose of this study was to investigate the association between TWM parameters and heart rate variability (HRV) during intradialytic monitoring. In each of 81 patients on maintenance HD, continuous electrocardiograms were recorded 5 times during HD on alternate weeks. TWM descriptors were calculated every 5 s in overlapping 10-s ECG segments and Low Frequency (LF) (0.04 Hz to 0.15 Hz), High Frequency (HF) (0.15 Hz to 0.40 Hz) powers of the spectrum of HRV were calculated every five min. The calculated values of TWM and HRV were averaged during the first hour of the recordings and subsequently over all recordings in each subject. Analyzable data for HRV and TWM were available in 71 HD patients (aged 61+/-15, 36 % diabetics, 32 % females). LF in normalized units correlated positively with Total Cosine R to T (r=0.374, p=0.001) and negatively with T wave morphology dispersion (r=-0.253, p=0.033) after adjusting for heart rate. A heart rate independent association between repolarisation descriptors and HRV exists in HD patients. Autonomic modulation needs to be considered when using TWM characteristics for risk profiling of HD patients.
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Affiliation(s)
- D Poulikakos
- Cardiovascular Sciences Research Centre, St. George's University of London, Medical School, London, UK.
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Xie Y, Izu LT, Bers DM, Sato D. Arrhythmogenic transient dynamics in cardiac myocytes. Biophys J 2014; 106:1391-7. [PMID: 24655514 DOI: 10.1016/j.bpj.2013.12.050] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 11/09/2013] [Accepted: 12/31/2013] [Indexed: 02/04/2023] Open
Abstract
Cardiac action potential alternans and early afterdepolarizations (EADs) are linked to cardiac arrhythmias. Periodic action potentials (period 1) in healthy conditions bifurcate to other states such as period 2 or chaos when alternans or EADs occur in pathological conditions. The mechanisms of alternans and EADs have been extensively studied under steady-state conditions, but lethal arrhythmias often occur during the transition between steady states. Why arrhythmias tend to develop during the transition is unclear. We used low-dimensional mathematical models to analyze dynamical mechanisms of transient alternans and EADs. We show that depending on the route from one state to another, action potential alternans and EADs may occur during the transition between two periodic steady states. The route taken depends on the time course of external perturbations or intrinsic signaling, such as β-adrenergic stimulation, which regulate cardiac calcium and potassium currents with differential kinetics.
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Affiliation(s)
- Yuanfang Xie
- Departments of Pharmacology, University of California Davis, Davis, California
| | - Leighton T Izu
- Departments of Pharmacology, University of California Davis, Davis, California
| | - Donald M Bers
- Departments of Pharmacology, University of California Davis, Davis, California
| | - Daisuke Sato
- Departments of Pharmacology, University of California Davis, Davis, California.
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AAGAARD PHILIP, BRAUNSCHWEIG FRIEDER, WECKE LILIANE, SAHLÉN ANDERS, BERGFELDT LENNART. Early Repolarization in Middle-Age Runners. Med Sci Sports Exerc 2014; 46:1285-92. [DOI: 10.1249/mss.0000000000000251] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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12
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Hillebrand S, de Mutsert R, Christen T, Maan AC, Jukema JW, Lamb HJ, de Roos A, Rosendaal FR, den Heijer M, Swenne CA. Body fat, especially visceral fat, is associated with electrocardiographic measures of sympathetic activation. Obesity (Silver Spring) 2014; 22:1553-9. [PMID: 24458875 DOI: 10.1002/oby.20709] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 01/21/2014] [Indexed: 02/01/2023]
Abstract
OBJECTIVE Obesity is associated with sympathetic activation, but the role of different fat depots is unclear. The association between body fat, specifically visceral fat, and electrocardiographic measures of sympathetic activation in a population with structurally normal hearts was investigated. METHODS In this cross-sectional baseline analysis of the Netherlands Epidemiology of Obesity study, body fat percentage was assessed with BIA and abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) with magnetic resonance (MR) imaging. Mean heart rate (HR) and five other electrocardiographic measures of sympathetic activation were calculated. We performed multivariate linear regression analyses. RESULTS In 868 participants with a mean age(SD) of 55(6) years, BMI of 26(4) kg/m(2) , 47% men, body fat was associated with HR and two other measures of sympathetic activation. Per sex-specific SD total body fat, the difference in HR was 1.9 beats/min (95% CI: 1.0, 2.9; P < 0.001) and per SD waist circumference 2.1 beats/min (95% CI: 1.3, 2.9; P < 0.001). The difference in HR per SD VAT was 2.1 beats/min (95% CI: 1.3, 3.0; P < 0.001). CONCLUSIONS Body fat, especially visceral fat, was associated with electrocardiographic measures of sympathetic activation. Our study implies that already before the onset of cardiovascular disease, excess (visceral) body fat is associated with sympathetic activation.
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Affiliation(s)
- Stefanie Hillebrand
- Department of Clinical Epidemiology, Leiden University Medical Centre, Leiden, the Netherlands
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Lingman M, Hartford M, Karlsson T, Herlitz J, Rubulis A, Caidahl K, Bergfeldt L. Transient repolarization alterations dominate the initial phase of an acute anterior infarction--a vectorcardiography study. J Electrocardiol 2014; 47:478-85. [PMID: 24891262 DOI: 10.1016/j.jelectrocard.2014.04.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To study effects of ischemia-reperfusion on ventricular electrophysiology in humans by three-dimensional electrocardiography. METHODS Fifty-seven patients with first-time acute anterior ST elevation myocardial infarction were monitored from admission and >24h after symptom onset with continuous vectorcardiography (VCG; modified Frank orthogonal leads). Global ventricular depolarization and repolarization (VR) measures were compared at maximum vs. minimum ST vector magnitude (STVM) (median 208; 111-303 vs. 362; 165-1359min after symptom onset). RESULTS At maximum vs. minimum STVM the Tarea (overall VR dispersion) almost tripled (118 vs. 41μVs; p<0.0001), the T-loop bulginess was 90% greater (Tavplan 0.91 vs 0.48μV; p<0.0001), and Tpeak-end/QT was 39% larger (0.32 vs 0.23; p<0.0001). QRSarea (overall dispersion of depolarization) was 12% larger at maximum STVM, while QRS duration was 10% longer at minimum STVM. CONCLUSIONS Ischemia-reperfusion was accompanied by profound and transient alterations of VR dispersion, while changes in depolarization were modest and delayed.
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Affiliation(s)
- Markus Lingman
- Institute of Medicine, Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Department of Medicine, Halland Hospital, Varberg, Sweden.
| | - Marianne Hartford
- Institute of Medicine, Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Thomas Karlsson
- Institute of Medicine, Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Johan Herlitz
- Institute of Medicine, Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Center of Prehospital Research in Western Sweden, University of Borås, Borås, Sweden
| | - Aigars Rubulis
- Institute of Medicine, Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Kenneth Caidahl
- Department of Clinical Physiology, Sahlgrenska University Hospital, Gothenburg, Sweden; Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Lennart Bergfeldt
- Institute of Medicine, Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Qiu Q, Liu W, Li J, Wei Y, Yang K, Suo W, Wu W, Du H, Zhang Y, Zhao G, Zhou Z, Zheng Y, Lin Y. Pharmacokinetics of Pilsicainide Hydrochloride for Injection in Healthy Chinese Volunteers: A Randomized, Parallel-Group, Open-Label, Single-Dose Study. Clin Ther 2014; 36:255-63. [DOI: 10.1016/j.clinthera.2013.12.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 12/11/2013] [Accepted: 12/28/2013] [Indexed: 11/15/2022]
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15
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Diamant UB, Vahedi F, Winbo A, Rydberg A, Stattin EL, Jensen SM, Bergfeldt L. Electrophysiological phenotype in the LQTS mutations Y111C and R518X in the KCNQ1 gene. J Appl Physiol (1985) 2013; 115:1423-32. [PMID: 24052033 DOI: 10.1152/japplphysiol.00665.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Long QT syndrome is the prototypical disorder of ventricular repolarization (VR), and a genotype-phenotype relation is postulated. Furthermore, although increased VR heterogeneity (dispersion) may be important in the arrhythmogenicity in long QT syndrome, this hypothesis has not been evaluated in humans and cannot be tested by conventional electrocardiography. In contrast, vectorcardiography allows assessment of VR heterogeneity and is more sensitive to VR alterations than electrocardiography. Therefore, vectorcardiography was used to compare the electrophysiological phenotypes of two mutations in the LQT1 gene with different in vitro biophysical properties, and with LQT2 mutation carriers and healthy control subjects. We included 99 LQT1 gene mutation carriers (57 Y111C, 42 R518X) and 19 LQT2 gene mutation carriers. Potassium channel function is in vitro most severely impaired in Y111C. The control group consisted of 121 healthy subjects. QRS, QT, and T-peak to T-end (Tp-e) intervals, measures of the QRS vector and T vector and their relationship, and T-loop morphology parameters were compared at rest. Apart from a longer heart rate-corrected QT interval (QT heart rate corrected according to Bazett) in Y111C mutation carriers, there were no significant differences between the two LQT1 mutations. No signs of increased VR heterogeneity were observed among the LQT1 and LQT2 mutation carriers. QT heart rate corrected according to Bazett and Tp-e were longer, and the Tp-e-to-QT ratio greater in LQT2 than in LQT1 and the control group. In conclusion, there was a marked discrepancy between in vitro potassium channel function and in vivo electrophysiological properties in these two LQT1 mutations. Together with previous observations of the relatively low risk for clinical events in Y111C mutation carriers, our results indicate need for cautiousness in predicting in vivo electrophysiological properties and the propensity for clinical events based on in vitro assessment of ion channel function alone.
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Affiliation(s)
- Ulla-Britt Diamant
- Department of Public Health and Clinical Medicine, Heart Centre, Umeå University, Umeå, Sweden
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16
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Vahedi F, Diamant UB, Lundahl G, Bergqvist G, Gransberg L, Jensen SM, Bergfeldt L. Instability of repolarization in LQTS mutation carriers compared to healthy control subjects assessed by vectorcardiography. Heart Rhythm 2013; 10:1169-75. [PMID: 23643511 DOI: 10.1016/j.hrthm.2013.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Indexed: 11/18/2022]
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 QT 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 Poincaré 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 QT 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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Affiliation(s)
- Farzad Vahedi
- Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
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