PO-05-082 ANTITACHYCARDIA PACING IS MORE EFFECTIVE WHEN DELIVERED TO THE LEFT BUNDLE BRANCH COMPARED TO THE RIGHT VENTRICLE IN A CANINE ISCHEMIC VENTRICULAR TACHYCARDIA MODEL

Abstract

Implantable cardioverter-defibrillators (ICDs) can terminate ventricular tachycardia (VT) with Antitachycardia pacing (ATP) delivered to a right ventricular (RV) pacing lead, thereby avoiding painful and damaging high-energy shocks. However, ATP efficacy is limited for fast VT, and ATP can accelerate VT or convert VT to ventricular fibrillation (VF). Physiological pacing delivered to the left bundle branch (LBB) has emerged as a clinically relevant target to minimize ventricular dyssynchrony and pacing-induced heart failure. ATP efficacy and safety delivered to the LBB are yet to be investigated. Evaluate the therapeutic efficacy and safety of ATP delivered to an LBB lead compared to ATP delivered to a conventional RV lead. In 6 anesthetized dogs, pacing leads from two ICDs (CobaltTM XT DR, Medtronic, Inc) were implanted at the RV apex (6947 Sprint Quattro SecureTM, Medtronic, Inc) and the LBB (3830 SelectSecureTM, Medtronic, Inc). A lateral thoracotomy procedure was performed, and a two-hour lateral anterior descending artery ischemia-reperfusion injury was caused. The thoracotomy was closed and on post-infarct day 4, dogs were anesthetized, and sustained VT episodes were induced by programmed electrical stimulation. ATP (up to 5 trains of 8 pulses at approximately 88% of the VT cycle length) was delivered to either the LBB or RV pacing site in a randomized fashion. The success rate of ATP in terminating the VT episodes and the rate of VT acceleration and degeneration into VF from both pacing locations were evaluated. In our canine ischemic VT model, VT was induced 80 times, with a mean VT cycle length of 178±35 ms. ATP was delivered and tested for each episode. For ATP delivered to the RV, the success rate for terminating VT was 54%. The success rate for terminating VT for ATP delivered to the LBB was 73% (Fig. A, p < 0.05). ATP resulted in VT acceleration for 10% and 5% of ATP attempts delivered to the RV and LV, respectively (Fig. B, p = Not Significant, NS). Degeneration to VF occurred for 5% of all ATP attempts delivered to the RV, and there was no such incident for ATP delivered to the LBB (Fig. B). Higher efficacy and lower incidence of VT acceleration were observed with ATP delivered to LBB compared to ATP delivered to the RV in this canine ischemic VT model. Improved performance of ATP delivered to LBB compared to RV provides additional incentive for expanded use of LBB leads for pacing and therapy delivery.