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Ifedili I, Maturana M, Kayali S, Levine Y, Kabra R, Jha SK. A case of short QT-interval postventricular arrhythmia arrest from Torsade De Pointes, a new phenotype, or the result of tachycardia-mediated imbalance. J Cardiovasc Electrophysiol 2024; 35:501-504. [PMID: 38174843 DOI: 10.1111/jce.16164] [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: 10/04/2023] [Revised: 12/03/2023] [Accepted: 12/15/2023] [Indexed: 01/05/2024]
Abstract
INTRODUCTION We report the case of an 18-year-old female with recurrent syncope that was discovered to have congenital long QT syndrome (LQTS) and episodes of a transiently short QT interval after spontaneous termination of polymorphic ventricular tachycardia. METHODS & RESULTS A cardiac event monitor revealed a long QT interval and initiation of polymorphic ventricular tachycardia by a premature ventricular complex on the preceding T-wave. After 1 minute of ventricular fibrillation, her arrhythmia spontaneously terminated with evidence of a short QT interval. CONCLUSIONS A transient, potentially artificial, short QT interval following Torsades de Pointes can occur in patients with LQTS.
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Affiliation(s)
- Ikechukwu Ifedili
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Miguel Maturana
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Sharif Kayali
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Yehoshua Levine
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Rajesh Kabra
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Kansas City Heart Rhythm Institute, Overland Park, Kansas, USA
| | - Sunil K Jha
- Department of Cardiovascular Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
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Intra-Individual Comparison of Sinus and Ectopic Beats Probing the Ventricular Gradient's Activation Dependence. J Cardiovasc Dev Dis 2023; 10:jcdd10020089. [PMID: 36826585 PMCID: PMC9964972 DOI: 10.3390/jcdd10020089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 02/04/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
Wilson assumed that the ventricular gradient (VG) is independent of the ventricular activation order. This paradigm has often been refuted and was never convincingly corroborated. We sought to validate Wilson's concept by intra-individual comparison of the VG of sinus beats and ectopic beats, thus assessing the effects of both altered ventricular conduction (caused by the ectopic focus) and restitution (caused by ectopic prematurity). We studied standard diagnostic ECGs of 118 patients with accidental extrasystoles: normally conducted supraventricular ectopic beats (SN, N = 6) and aberrantly conducted supraventricular ectopic beats (SA, N = 20) or ventricular ectopic beats (V, N = 92). In each patient, we computed the VG vectors of the predominant beat, VGp→, of the ectopic beat, VGe→, and of the VG difference vector, ΔVGep→, and compared their sizes. VGe→ of the SA and V ectopic beats were significantly larger than VGp→ (53.7 ± 25.0 vs. 47.8 ± 24.6 mV∙ms, respectively; p < 0.001). ΔVGep→ were three times larger than the difference of VGe→ and VGp→ (19.94 ± 9.76 vs. 5.94 mV∙ms, respectively), demonstrating differences in the VGp→ and VGe→ spatial directions. The amount of ectopic prematurity was not correlated with ΔVGep→, although the larger VG difference vectors were observed for the more premature (<80%) extrasystoles. Electrical restitution properties and electrotonic interactions likely explain our findings. We conclude that the concept of a conduction-independent VG should be tested at equal heart rates and without including premature extrasystoles.
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Świerżyńska E, Oręziak A, Główczyńska R, Rossillo A, Grabowski M, Szumowski Ł, Caprioglio F, Sterliński M. Rate-Responsive Cardiac Pacing: Technological Solutions and Their Applications. SENSORS (BASEL, SWITZERLAND) 2023; 23:s23031427. [PMID: 36772467 PMCID: PMC9920425 DOI: 10.3390/s23031427] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/18/2023] [Accepted: 01/20/2023] [Indexed: 05/12/2023]
Abstract
Modern cardiac pacemakers are equipped with a function that allows the heart rate to adapt to the current needs of the patient in situations of increased demand related to exercise and stress ("rate-response" function). This function may be based on a variety of mechanisms, such as a built-in accelerometer responding to increased chest movement or algorithms sensing metabolic demand for oxygen, analysis of intrathoracic impedance, and analysis of the heart rhythm (Q-T interval). The latest technologies in the field of rate-response functionality relate to the use of an accelerometer in leadless endocavitary pacemakers; in these devices, the accelerometer enables mapping of the mechanical wave of the heart's work cycle, enabling the pacemaker to correctly sense native impulses and stimulate the ventricles in synchrony with the cycles of atria and heart valves. Another modern system for synchronizing pacing rate with the patient's real-time needs requires a closed-loop system that continuously monitors changes in the dynamics of heart contractions. This article discusses the technical details of various solutions for detecting and responding to situations related to increased oxygen demand (e.g., exercise or stress) in implantable pacemakers, and reviews the results of clinical trials regarding the use of these algorithms.
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Affiliation(s)
- Ewa Świerżyńska
- Department of Arrhythmia, The Cardinal Stefan Wyszynski National Institute of Cardiology, 04-628 Warsaw, Poland
- 1st Department of Cardiology, Medical University of Warsaw, 02-097 Warsaw, Poland
- Correspondence:
| | - Artur Oręziak
- Department of Arrhythmia, The Cardinal Stefan Wyszynski National Institute of Cardiology, 04-628 Warsaw, Poland
| | - Renata Główczyńska
- 1st Department of Cardiology, Medical University of Warsaw, 02-097 Warsaw, Poland
| | - Antonio Rossillo
- Department of Cardiology, San Bortolo Hospital, 36100 Vicenza, Italy
| | - Marcin Grabowski
- 1st Department of Cardiology, Medical University of Warsaw, 02-097 Warsaw, Poland
| | - Łukasz Szumowski
- Department of Arrhythmia, The Cardinal Stefan Wyszynski National Institute of Cardiology, 04-628 Warsaw, Poland
| | | | - Maciej Sterliński
- Department of Arrhythmia, The Cardinal Stefan Wyszynski National Institute of Cardiology, 04-628 Warsaw, Poland
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Omondi A, Sirinvaravong N, Spears J, Sauerwein S, Taoutel R, Liskov S, Gao C, Liu T, Kowey PR, Yan GX. Marked QTc Reduction Immediately Following Direct Current Cardioversion of Atrial Fibrillation: Clinical Implications and Mechanisms. JACC Clin Electrophysiol 2022; 9:543-554. [PMID: 36752461 DOI: 10.1016/j.jacep.2022.10.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/12/2022] [Accepted: 10/19/2022] [Indexed: 01/20/2023]
Abstract
BACKGROUND The QTc in sinus rhythm (SR) following direct current cardioversion (DCCV) of atrial fibrillation (AF) is commonly used as a baseline QTc for patients who require initiation of antiarrhythmic drugs for rhythm control. Inaccurate baseline QTc may cause drug-induced torsades de pointes. OBJECTIVES To assess time-dependent QTc changes following DCCV. METHODS We prospectively assessed QTc changes with Bazett's QTc and Fridericia's QTc formulas in 65 patients following conversion of AF to SR. Among these 65 patients, 48 underwent DCCV and 17 spontaneously converted to SR. RESULTS There was a large and statistically significant decrease in QTc in SR immediately following DCCV in 40 patients, which occurred with an abrupt reduction in heart rate postcardioversion. This finding excluded 8 patients with ventricular-paced QRS. The mean decrease from QTc in AF was 70.7 ± 37.2 milliseconds in the QTc interval for heart rate using Bazett's formula and 33.8 ± 17.9 milliseconds in the QTc interval for heart rate using Fridericia's formula at 1-minute post-DCCV. In 17 patients with spontaneous conversion from AF to SR, the QTc reduction was comparable to those in patients with DCCV. The QTc increased with time and reached a steady state at 5 minutes following conversion. Initiation of class III drugs based on the "shortened" baseline QTc following DCCV was associated with drug-induced torsades de pointes. CONCLUSIONS In patients with AF following conversion, regardless spontaneous or DCCV, the QTc shortened significantly with decreases in heart rate, likely via the mechanism of time-dependent rate adaption of ventricular repolarization. A steady-state QTc at 5-minutes following DCCV should be used as real baseline for guidance of pharmacotherapy in patients with AF.
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Affiliation(s)
- Arthur Omondi
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Natee Sirinvaravong
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Jenna Spears
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Samuel Sauerwein
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Roy Taoutel
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Steven Liskov
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Chuanyu Gao
- Fuwai Huazhong Hospital, Zhengzhou, Henan, China.
| | - Tong Liu
- Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
| | - Peter R Kowey
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA; Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Gan-Xin Yan
- Lankenau Medical Center and Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA; Fuwai Huazhong Hospital, Zhengzhou, Henan, China; Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania, 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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Discussion on Repolarization Reserve between Patients with Coronary Heart Disease and Normal Controls. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2022; 2022:7944969. [PMID: 36035296 PMCID: PMC9410869 DOI: 10.1155/2022/7944969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 07/20/2022] [Accepted: 07/29/2022] [Indexed: 11/17/2022]
Abstract
Objective To investigate the repolarization reserve of normal controls (NCs) and patients with coronary heart disease (CHD). Methods From January 1st, 2010 to December 31st, 2018, 200 age- and gender-matched inpatients in the Second Hospital of Shanxi Medical University and Heji Hospital Affiliated to Changzhi Medical College were selected for treadmill exercise test (TET), including 67 patients in the myocardial ischemia group, 66 patients in the suspected myocardial ischemia group, and 67 patients in the normal control group. Coronary angiography (CAG) was performed on 49 of 133 patients in the myocardial ischemia group and the suspected myocardial ischemia group, and 9 positives and 40 negatives were identified. The heart rate (HR) and QT interval of TET examiners before exercise, during exercise (90 beats/min, 120 beats/min, maximum HR), and in the recovery period (1 minute and 3 minutes after exercise) were reviewed, and QTc values were calculated after being corrected by BaZett's. Results The mean QTc values in NCs were all below 452 ms, before exercise, during exercise (90 beats/min, 120 beats/min and maximum HR), and during the recovery period (1 minute and 3 minutes after exercise). The comparison results of the RR interval between the two groups revealed P > 0.05, indicating no statistical significance. Significant differences were present when comparing the QT intervals when the HRs were 90 beats/minute and 120 beats/minute during exercise (P < 0.05). And comparing the QTc values, it was found that the QTc values during different exercise periods were statistically different between groups (P < 0.05). Conclusions NCs have good repolarization reserve. CAG can confirm true myocardial ischemia patients (i.e., patients with CHD) among myocardial ischemia and suspected myocardial ischemia patients screened by TET. Patients with positive CAG have poor repolarization reserve as QT interval represents ventricular repolarization adaptability.
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Andršová I, Hnatkova K, Šišáková M, Toman O, Smetana P, Huster KM, Barthel P, Novotný T, Schmidt G, Malik M. Sex and Rate Change Differences in QT/RR Hysteresis in Healthy Subjects. Front Physiol 2022; 12:814542. [PMID: 35197861 PMCID: PMC8859307 DOI: 10.3389/fphys.2021.814542] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 12/15/2021] [Indexed: 11/13/2022] Open
Abstract
While it is now well-understood that the extent of QT interval changes due to underlying heart rate differences (i.e., the QT/RR adaptation) needs to be distinguished from the speed with which the QT interval reacts to heart rate changes (i.e., the so-called QT/RR hysteresis), gaps still exist in the physiologic understanding of QT/RR hysteresis processes. This study was designed to address the questions of whether the speed of QT adaptation to heart rate changes is driven by time or by number of cardiac cycles; whether QT interval adaptation speed is the same when heart rate accelerates and decelerates; and whether the characteristics of QT/RR hysteresis are related to age and sex. The study evaluated 897,570 measurements of QT intervals together with their 5-min histories of preceding RR intervals, all recorded in 751 healthy volunteers (336 females) aged 34.3 ± 9.5 years. Three different QT/RR adaptation models were combined with exponential decay models that distinguished time-based and interval-based QT/RR hysteresis. In each subject and for each modelling combination, a best-fit combination of modelling parameters was obtained by seeking minimal regression residuals. The results showed that the response of QT/RR hysteresis appears to be driven by absolute time rather than by the number of cardiac cycles. The speed of QT/RR hysteresis was found decreasing with increasing age whilst the duration of individually rate corrected QTc interval was found increasing with increasing age. Contrary to the longer QTc intervals, QT/RR hysteresis speed was faster in females. QT/RR hysteresis differences between heart rate acceleration and deceleration were not found to be physiologically systematic (i.e., they differed among different healthy subjects), but on average, QT/RR hysteresis speed was found slower after heart rate acceleration than after rate deceleration.
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Affiliation(s)
- Irena Andršová
- Faculty of Medicine, Department of Internal Medicine and Cardiology, University Hospital Brno, Masaryk University, Brno, Czechia
| | - Katerina Hnatkova
- National Heart and Lung Institute, Imperial College, London, United Kingdom
| | - Martina Šišáková
- Faculty of Medicine, Department of Internal Medicine and Cardiology, University Hospital Brno, Masaryk University, Brno, Czechia
| | - Ondřej Toman
- Faculty of Medicine, Department of Internal Medicine and Cardiology, University Hospital Brno, Masaryk University, Brno, Czechia
| | | | - Katharina M Huster
- Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Petra Barthel
- Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Tomáš Novotný
- Faculty of Medicine, Department of Internal Medicine and Cardiology, University Hospital Brno, Masaryk University, Brno, Czechia
| | - Georg Schmidt
- Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Marek Malik
- National Heart and Lung Institute, Imperial College, London, United Kingdom.,Faculty of Medicine, Department of Internal Medicine and Cardiology, Masaryk University, Brno, Czechia
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Lindsey ML, LeBlanc AJ, Ripplinger CM, Carter JR, Kirk JA, Hansell Keehan K, Brunt KR, Kleinbongard P, Kassiri Z. Reinforcing rigor and reproducibility expectations for use of sex and gender in cardiovascular research. Am J Physiol Heart Circ Physiol 2021; 321:H819-H824. [PMID: 34524922 DOI: 10.1152/ajpheart.00418.2021] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Merry L Lindsey
- Department of Cellular and Integrative Physiology, Center for Heart and Vascular Research, University of Nebraska Medical Center, Omaha, Nebraska.,Research Service, Nebraska-Western Iowa Health Care System, Omaha, Nebraska
| | - Amanda J LeBlanc
- Department of Physiology and Cardiovascular Innovation Institute, University of Louisville, Louisville, Kentucky
| | | | - Jason R Carter
- Department of Health and Human Development, Montana State University, Bozeman, Montana
| | - Jonathan A Kirk
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Chicago, Illinois
| | - Kara Hansell Keehan
- Strategic Journal Development, American Physiological Society, Rockville, Maryland.,AJP-Heart and Circulatory Physiology, American Physiological Society, Rockville, Maryland
| | - Keith R Brunt
- Department of Pharmacology, Faculty of Medicine, Dalhousie University, Saint John, New Brunswick, Canada
| | - Petra Kleinbongard
- Institute for Pathophysiology, West German Heart and Vascular Center, University of Essen Medical School, Essen, Germany
| | - Zamaneh Kassiri
- Department of Physiology, Cardiovascular Research Center, University of Alberta, Edmonton, Alberta, Canada
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Axelsson KJ, Gransberg L, Lundahl G, Bergfeldt L. Adaptation of ventricular repolarization dispersion during heart rate increase in humans: A roller coaster process. J Electrocardiol 2021; 68:90-100. [PMID: 34411881 DOI: 10.1016/j.jelectrocard.2021.07.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/10/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022]
Abstract
BACKGROUND Regional differences in ventricular activation sequence and action potential duration and morphology result in dispersion in ventricular repolarization (VR). VR dispersion is a key factor in arrhythmogenesis. We studied the adaptation of global VR dispersion in humans during normal and abnormal ventricular activation, and the relation to the QT adaptation (hysteresis). METHODS We measured global VR dispersion as T amplitude, T area, and ventricular gradient (VG), using continuous Frank vectorcardiography, in response to abrupt and sustained atrial (AP) or ventricular pacing (VP) aiming at 120 bpm, in 21 subjects with permanent pacemakers. RESULTS Following pacing start, VR adaptation showed an initially rapid and complex tri-phasic pattern, most pronounced for T amplitude. There were major differences in the patterns of VR dispersion adaptation following abrupt AP vs VP, confirming that the adaptation pattern is activation dependent. In response to AP, an instantaneous decrease in VR dispersion occurred, followed by an increase and then a slow decrease, all at a lower level than baseline. In contrast, following VP there was an immediate increase to ~4× baseline in T amplitude and T area (but not in VG), with a subsequent biphasic adaptation lasting longer during VP than AP. The initial rapid changes occurred within the time for QT adaptation to reach steady-state. CONCLUSIONS Our results corroborate and expand data from animal and invasive human studies, showing similarities of the adaptation pattern on different scales. The initial rapidly changing VR adaptation phase presumably reflects a window of increased vulnerability to arrhythmias.
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Affiliation(s)
- Karl-Jonas Axelsson
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Region Västra Götaland, Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
| | - Lennart Gransberg
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Gunilla Lundahl
- 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 Västra Götaland, Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
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