Assessment of the SyncAV fusion pacing algorithm on exercise capacity in patients with cardiac resynchronisation therapy device

Abstract

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation (BHF) and Local Departmental Research Funding Background Fusion pacing as part of cardiac resynchronization therapy (CRT) requires correct timing of left ventricular pacing to right ventricular activation. The SyncAV algorithm, available in Quadra Allure and Assura CRT devices, is designed to allow optimal fusion pacing by dynamic reassessment of intrinsic atrio-ventricular (AV) conduction to adjust the paced/sensed AV delay. However, it is unclear whether AV optimisation continues to maintain resynchronisation during exercise, or whether potential loss of fusion pacing with changes in intrinsic AV conduction could lead to decreased exercise capacity. Cardio-pulmonary exercise testing (CPET) is the gold standard method for assessing exercise performance. Purpose To assess exercise capacity using the SyncAV algorithm for fusion pacing, compared with conventional biventricular pacing with fixed AV delays (AVD) for CRT. Methods Patients at least 6 months post-CRT implant were recruited in a prospective single-centre randomized single-blind crossover study. Patients performed 2 CPET tests at least 1 week apart, with randomization to either SyncAV with fusion pacing or conventional biventricular pacing with a fixed AVD of 120ms. All other programming was optimised to produce the narrowest QRS duration possible at rest in each case. Results Nine patients (5 male, age 70 ± 10 years, mean ± standard deviation) were recruited, with both ischaemic and non-ischaemic aetiology of heart failure. All had clinical or echocardiographic response to CRT. There was no difference in peak oxygen consumption (V̇O2max) between programming (1.47 ± 0.57 vs 1.50 ± 0.65 l/min for fixed AVD and SyncAV groups respectively, p = 0.59), or oxygen consumption at anaerobic threshold (VT1) (0.72 ± 0.20 vs 0.74 ± 0.25 l/min, p = 0.57). There was no difference in oxygen pulse (V̇O2/heart rate - a surrogate of stroke volume) at peak (12.3 ± 3.8 vs 13 ± 5.0 ml/beat , p = 0.28) or VT1 (8.4 ± 2.2 vs 8.7 ± 2.1 ml/beat, p = 0.67) and also no change in time to V̇O2max (1400 ± 491 vs 1367 ± 543 seconds, p = 0.38) or VT1 (518 ± 211 vs 534 ± 200 seconds, p = 0.75). Average heart rate at the median stage of exercise showed no difference between programming (96 ± 18 vs 93 ± 15 bpm respectively, p = 0.32). There was no difference in BORG Rating of Perceived Exertion (BORG-RPE) score at either peak exercise (median 19 [interquartile range (IQR) 2] vs 17 [IQR 2], p = 0.23) or at the median stage of exercise (median 13 [IQR 1] vs 13 [IQR 2], p = 0.30). Conclusion Fusion pacing using the SyncAV algorithm does not appear to improve exercise capacity compared to optimised conventional biventricular pacing with fixed AVD.