Abstract
BACKGROUND: Cardiac resynchronization therapy (CRT) response relies on 2 factors: when and where to pace. These factors may be enhanced by dynamic atrioventricular delays (AVDs) (eg, SyncAV CRT, Abbott Cardiovascular, Abbott Park, IL) and multisite left ventricular (LV) pacing (eg, MultiPoint Pacing [MPP], Abbott). Their individual and combined synchronization contributions have not been evaluated across a comprehensive spectrum of pacing configurations. The objective is to distinguish the acute electrical synchrony achieved by static vs dynamic AVDs, single-site vs multisite LV pacing, and with vs without right ventricular (RV) pacing. METHODS: CRT-indicated patients with left bundle branch block (LBBB) and intact atrioventricular (AV) conduction (PR < 250 ms) were enrolled and evaluated during implant. Acute changes in 12-lead electrocardiographic (ECG) QRS duration (QRSd) were evaluated during intrinsic conduction, biventricular pacing (BiV), biventricular MPP, LV-only single-site pacing (LVSS), and LV-only MPP (LVMPP). CRT modes were evaluated with static AVDs and optimized SyncAV AVDs. RESULTS: CRT implant and QRSd evaluation were completed in 85 patients (71% male, 34% ischemic, 179 ms PR). The median intrinsic QRSd of 165 ms was reduced by BiV, MPP, LVSS, and LVMPP without SyncAV to 144 ms (by 14%), 142 ms (16%), 155 ms (8%), and 149 ms (12%), respectively (P < 0.01 vs intrinsic). BiV + SyncAV, MPP + SyncAV, LVSS + SyncAV, and LVMPP + SyncAV reduced the intrinsic QRSd significantly further to 128 ms (by 23%), 124 ms (26%), 131 ms (21%), and 129 ms (24%) (P < 0.0001, each corresponding pair). CONCLUSIONS: MPP combined with SyncAV achieved the narrowest QRSd, in the overall population and in the most patients, by delivering ventricular pacing from all available sites (RV + LV1 + LV2) while timed with dynamic AVDs. CLINICAL REGISTRATION NUMBER: NCT03567096.