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Short-term variability of repolarization is equally modulated by atrial and (bi)ventricular high rate pacing in patients with an indication for an implantable cardioverter defibrillator. Europace 2021. [DOI: 10.1093/europace/euab116.369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Dutch Heart Foundation
Background
An increase in temporal dispersion of repolarization, quantified as short-term variability of the QT-interval (STV-QT), precedes ventricular arrhythmias and has therefore been proposed as a marker for monitoring of imminent arrhythmic risk. A reversal of an increased STV by high rate pacing at 100 bpm was anti-arrhythmic in the chronic atrioventricular block dog model susceptible to Torsade de Pointes arrhythmias upon challenge with an IKr-blocker. The objective of the current study was to investigate the physiological modulation of STV by pacing in patients with an indication for an implantable cardioverter defibrillator (ICD), and to compare atrial and ventricular pacing.
Methods
ECG recordings were obtained with a sampling frequency of 1200 Hz in 10 dual chamber ICD patients and 10 patients with cardiac resynchronization therapy with defibrillation function (CRT-D) during the implantation or replacement. One-minute recordings were made during sinus rhythm (SR), and during pacing at 80 and 100 beats per minute (bpm) from the atrium (AAI), atrium and right ventricle (DDD RVp), and during atrio-biventricular pacing (DDD BiVp). The QT-interval was determined offline with fiducial segment averaging at one minute of each pacing rate, and 31 consecutive beats were used to calculate STV-QT with the following formula: ∑|D(n + 1)-Dn |/(N×√2), where D represents the determinant of repolarization (in this case the QT interval), and N represents the number of beats taken into account minus 1.
Results
In the patients overall, STV-QT decreased from 1.27 ± 0.38 ms in SR (±58 bpm) to 0.86 ± 0.26 ms* during AAI80, and to 0.68 ± 0.22 ms*† during AAI100 (*p < 0.05 compared to SR, †p < 0.05 compared to 80 bpm). The same decrease was seen during DDD80 RVp (0.81 ± 0.28 ms*) and during DDD100 RVp (0.66 ± 0.22 ms*†) (fig. 1). Additionally, DDD BiVp decreased STV-QT to 0.78 ± 0.20 ms* at 80 bpm and to 0.62 ± 0.19 ms* at 100 bpm in CRT-D patients (fig. 2).
Conclusion
Pacing at 80 and 100 bpm decreases STV-QT compared to sinus rhythm both in dual chamber ICD patients and CRT-D patients. The modulation of STV-QT is similar during atrial, and atrio- right ventricular and atrio-biventricular pacing. Abstract Figure. Modulation of STV-QT by AAI and DDD RVp
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High rate pacing guided by short-term variability of repolarization prevents imminent ventricular arrhythmias autonomically by an ICD. Eur Heart J 2020. [DOI: 10.1093/ehjci/ehaa946.0786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Background
The anesthetized, chronic complete atrioventricular block (CAVB) dog model allows reproducible inducibility of Torsade de Pointes (TdP) arrhythmias due to ventricular remodeling and after a challenge with an IKr-blocker. High rate pacing (HRP) prevents ventricular arrhythmias, but has long-term detrimental effects on cardiac function when applied continuously. Temporal dispersion of repolarization, quantified as short-term variability (STV), increases prior to ventricular arrhythmias and has been proposed as a marker to guide HRP.
Purpose
A proof-of-principle study to show STV determined automatically and in real-time by an ICD can guide HRP to prevent imminent ventricular arrhythmias.
Methods
Eight CAVB dogs were implanted with an ICD (Medtronic, lead in the right ventricular (RV) apex), with software to automatically determine STV online (STV-ICD). STV was determined from the activation recovery interval (ARI) of 31 consecutive beats with the formula: STV = Σ|ARI(n+1) − ARI(n)|/(N*√2). The CAVB dogs were challenged twice with dofetilide (0.025 mg/kg i.v. in 5 minutes or until the first TdP). In the first experiment, the individual STV-ICD threshold was determined prior to the first arrhythmic event and programmed into the ICD. In a serial experiment, HRP was initiated automatically once the STV-ICD threshold was reached, by gradually increasing the heart rate to 100 bpm. Occurrence of TdPs was monitored for 10 minutes from the start of dofetilide infusion in both experiments. During HRP, STV was measured offline from RV electrograms (EGM) and left ventricular (LV) monophasic action potential durations (MAPD) (STV-offline).
Results
During the inducibility experiment, 8/8 dogs had repetitive TdPs and STV-ICD increased from 0.96±0.42 to 2.10±1.26 ms* (*p<0.05). During the prevention experiment, all dogs reached the STV threshold. HRP decreased STV-offline from 2.02±1.12 to 0.78±0.28 ms*, which was accompanied by prevention of TdPs in 7/8 dogs* (Figure 1).
Conclusion
Temporal dispersion of repolarization, quantified as STV, can guide HRP automatically by an ICD to prevent ventricular arrhythmias.
Funding Acknowledgement
Type of funding source: Public grant(s) – National budget only. Main funding source(s): Dutch Heart Foundation Public Private Partnership
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Atrial dilation as a substrate for atrial fibrillation in the canine complete chronic atrioventricular block model. Eur Heart J 2020. [DOI: 10.1093/ehjci/ehaa946.0471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Background
Atrial fibrillation (AF) is the most common cardiac arrhythmia treated in clinical practice. Structural remodeling is characterized by atrial enlargement and contributes to the therapeutic resistance in patients with long-standing AF.
Purpose
To study the atrial arrhythmogenic and echocardiographic consequences induced by volume overload in the complete chronic atrioventricular block (CAVB) dog.
Methods
Echocardiographic and electrophysiological data was obtained in 14 anaesthetized Mongrel dogs, in acute AV-block (AAVB), after 6 weeks of CAVB (CAVB6) and CAVB10. Left atrial (LA) volume was determined with 2D echocardiography by using the biplane method. An electrocardiogram and monophasic action potentials (MAP) at the right atrial (RA) free wall were recorded. Atrial effective refractory period (AERP) was determined by continuous programmed electrical stimulation (PES) of 20 beats with a cycle length of 400 ms and an extrastimulus with decremental design until refractoriness was reached. A continuous PES protocol of 20 beats with an extrastimulus 5 ms longer than the AERP was applied for 150 seconds to trigger AF. After 5 min without arrhythmias, autonomic neuromodulation was performed by intravenous infusion (IV) of acetylcholine (1,5μg/kg/min to 6,0μg/kg/min) for 20 min followed by prompt IV infusion of isoprenaline (3μg/min) until the atrial heart rate increased by 20 bpm. PES with an extrastimulus was repeated for 150 seconds to induce AF.
Results
LA volume increased from 13.7±3.2 ml at AAVB to 20.5±5.9 ml* at CAVB6, and 22.7±6.0 ml* at CAVB10 (Fig. 1A). AERP was similar at AAVB, CAVB6, and CAVB10 (115.8±11.9, 117.3±11.7, and 106.8±12.1 ms respectively). Repetitive AF paroxysms of >10 seconds were induced in 1/14 (7%) dogs at AAVB, 1/11 (9%) at CAVB6, and 5/10 (50%)* at CAVB10 (*p<0.05) upon PES (Fig. 1B). Combined neuromodulation and PES did not increase the AF inducibility rate, but prolonged the longest episode of AF in the inducible dogs from 55±49 seconds to 236±202 seconds* at CAVB10 (Fig. 1C). LA volume was higher in inducible dogs 25.0±4.9 ml compared to 18.4±4.2 ml in non-inducible dogs at CAVB10.
Conclusion
Sustained atrial dilation forms a substrate for repetitive paroxysms of AF. Neuro-modulation prolongs AF episode duration in susceptible dogs. This animal model can be used to study structural remodeling of the atria and possible therapeutic advances in the management of AF.
Figure 1
Funding Acknowledgement
Type of funding source: Private company. Main funding source(s): Amgen Research
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