The functional differences between biventricular (BiV) endocardial and epicardial pacing in a dyssynchronous left ventricle are dependent on atrioventricular (AV) delay

Abstract

Biventricular (BiV) pacing is used to reduce electromechanical dyssynchrony in patients with left bundle branch block (LBBB). LV lead placement is limited by the patient's anatomy and condition, yielding controversy over selecting an optimal pacing site. We hypothesized that the addition of a LV stimulus that restores transmural activation sequence at late‐activated regions is an important determinant of improved LV function.To test this hypothesis, dyssynchrony (simLBBB) was produced in open‐chest dogs (n=6). We compared the effects of an additional LV stimulus at late (94.1 ms) activated regions during endocardial (Endo) and epicardial (Epi) pacing at varying atrioventricular (AV) delay. Regional deformation was assessed by biplane cineradiography of implanted beads.Compared to baseline, simLBBB significantly reduced LV function. Compared to simLBBB, BiV Endo pacing (AV delay of 40 ms) significantly improved systolic function: dPdt max (51%), LVESP (48.8 %), and E33 (0.55). BiV Epi pacing (AV delay of 40 ms) did not differ from simLBBB. At higher AV delays (80–130 ms), BiV Epi pacing significantly improved systolic function, however this improvement was less than BiV Endo pacing.We conclude that Endo LV pacing has a functional advantage over Epi LV pacing. Endo LV pacing in late‐activated regions may serve to reduce electrical and mechanical dyskinesis, thereby improving ventricular performance.