PO-02-014 IMPACT OF RIGHT VENTRICULAR ELECTRICAL ACTIVATION (INTRINSIC AND PACED) IN HEART FAILURE PATIENTS WITH LBBB

Abstract

The appropriately timed incorporation of the intrinsic right bundle branch (RBB) conduction during biventricular (RV & LV) pacing – “triple fusion”- may improve electrical resynchronization and response to CRT. However, the relative contribution of these wavefronts, optimal programming, and impact upon left ventricular activation remains poorly understood. To characterize intrinsic RBB and paced RV activation in heart failure patients with LBBB. CRT Patients with Strauss-type LBBB were studied. Right ventricular electrical activation was estimated from the onset of the r wave to the nadir of the S wave (rS interval) in leads V1 and V2. QRS duration was taken as the earliest onset to the terminal deflection in any lead. Paced QRS was measured during RV only pacing and nominal BiV (BiVNom; paced and sensed AV delay of 140/110 ms). The optimal AV delay was determined by the narrowest QRS duration achieved during simultaneous BiV pacing (BiVOpt) while adjusting the paced AV delay from 60% to 95% of the PR interval (in increments of 5%). This protocol was repeated while withholding RV pacing (LV-onlyOpt). All measurements were performed in each patient. Thirty patients (53% Male, 33% ICM, 68±8 yrs, EF 24±7%, qRV 25±8 ms, qLV 123±21 ms, and QRSd 170±18 ms) were evaluated. The PR interval was 208±39 ms (range 117-328 ms). The qlV/ QRS was 73±9%, indicating optimized LV lead position. Compared to BiVNom, BiVOpt was achieved at longer AVD (80±7% vs 56±7% of PR interval) but resulted in more rapid RBB electrical activation (59±14 ms vs 90±20 ms) and narrower QRS duration (130±13 ms vs 146±16 ms); all P < 0.05 vs BiVNom. Withholding RV pacing (LV-onlyOpt) did not impact RBB activation or AV delay programming compared to BiVOpt, but still reduced QRS duration compared to BiVNom (139±14 ms vs 146±16 ms; P<0.05). Incorporation of RV pacing during biventricular pacing with longer AVD programming facilitates intrinsic RBB conduction to improve electrical resynchronization without committing the LV to this wavefront.