Abstract: Background – Conventional, effective treatment of high-grade atrioventricular block (AVB) involves a single endocardial pacing lead positioned near the right ventricular apex (RVA). Other pacing sites might produce less cardiac dyssynchrony and better left ventricular (LV) function.
Hypothesis/Objectives – Endocardial pacing at the cranioventral RV outflow tract (RVOT) might differ hemodynamically from RVA pacing.
Animals – Client-owned dogs (n=8) with high-grade AVB.
Methods – Prospective, within-subjects comparisons (paired t-tests) of select ECG, LV synchrony and systolic function indices were made between pacing sites. Single plane (apical 2-chamber) transesophageal echocardiography (TEE) and multiple-lead ECG recordings were obtained. After transitioning from transcutaneous to temporary endocardial pacing using the permanent lead, data were collected at 100 pulses/minute following a standardized acclimation period during both RVOT and RVA pacing (Table). LV global and endocardial longitudinal strain (GLS, ELS), SD of time to peak strain, single-plane ejection fraction (EF) and stroke volume, and QRS duration were measured/calculated.
Results – Mean EF was higher in the RVOT (p=0.02). ELS for RVOT pacing was -23.1% vs. -20.4% for the RVA (p=0.072) but with no difference in mean GLS. QRS durations were longer in the RVOT site. No intra- or postoperative complications occurred.
Conclusions and Clinical Importance – This feasibility study was not sufficiently powered to evaluate superiority of lead positioning, but the data to test this hypothesis can be obtained safely, ideally with multiple LV planes and endocardial ECG recordings.
