Single-site ventricular pacing results in dyssynchronous ventricular activation and may contribute to ventricular dysfunction. We evaluated epicardial biventricular (BiV) pacing as a means of maintaining synchronous ventricular activation in an acute piglet model of AV block with normal ventricular anatomy and function.Methods and Results
We used left ventricular (LV) impedance catheters and tissue Doppler imaging to assess the cardiodynamics of immature piglets (n = 6, 33–78 days, 9.35 ± 0.85 kg). Following catheter ablation of the AV node, a pacemaker was programmed 20 beats per minute above the intrinsic atrial rate. The animals were paced at 5-minute intervals via the following AV sequential configurations: Right atrial appendage (RA)-RV apex (RVA), RA-LV apex (LVA), and RA-biventricular (RVA/LVA). RA-RVA was the experimental control. LV systolic mechanics, measured by the slope of the end-systolic pressure–volume relationship (Ees), increased with BiV pacing (12.8 ± 3.4 mmHg/mL, P < 0.02) or single-site LVA pacing (10.6 ± 3.4 mmHg/mL, P < 0.05) compared with single-site RVA pacing (8.3 ± 1.4 mmHg/mL). QRS duration lengthened compared with sinus rhythm (42 ± 8 msec) with either RVA (56 ± 9 msec, P < 0.02) or LVA (54 ± 7 msec, P < 0.03), but not with BiV (48 ± 7 msec, P = 0.08) pacing. Tissue Doppler imaging showed LV dyssynchrony with RVA (septal-to-lateral delay 46.0 ± 51.7 msec), with return toward normal with LVA (−9.6 ± 33.6 msec, P < 0.04) or BiV (−4.1 ± 33.8 msec, P < 0.04) pacing.Conclusions
In this acute immature piglet model of AV block, LV performance improved with single-site pacing from the LVA and BiV pacing (RVA/LVA), as compared with single-site pacing from the RVA. These changes correlated with tissue Doppler indices of mechanical synchrony, though not necessarily with QRS duration.