Left ventricular performance during triggered left ventricular pacing in patients with cardiac resynchronization therapy and left bundle branch block.

Purpose: To assess the acute effect of triggered left ventricular pacing (tLVp) on left ventricular performance and contraction pattern in patients with heart failure, left bundle branch block (LBBB), and cardiac resynchronization therapy (CRT).

Methods: Twenty-three patients with pre-implant QRS complex >150 ms, QRS complex narrowing under CRT, and sinus rhythm were included ≥3 months after CRT implantation. Echocardiographic assessment of left ventricular ejection fraction (LVEF), global peak systolic longitudinal strain (GLS), and contraction pattern by 2D strain was performed during intrinsic conduction, tLVp, and BiV pacing and compared as paired data. Echocardiographic analysis was done blinded with respect to pacing mode.

Results: LVEF was significantly higher during BiV pacing (47 ± 11 %) compared with intrinsic conduction (43 ± 13 %, P = 0.001) and tLVp (44 ± 13 %, P = 0.001), while there was no difference between intrinsic conduction and tLVp (P = 0.28). GLS was higher during BiV (14 ± 3) than during intrinsic conduction (13 ± 3, P = 0.01) and tLVp (13 ± 3, P = 0.03). Difference in time-to-peak contraction between the basal septal and lateral walls was shorter during BiV pacing (-3 ± 44 ms) than during intrinsic conduction (129 ± 66, P < 0.001) and tLVp (118 ± 118 ms, P < 0.001), with no difference between tLVp and intrinsic conduction (P = 0.56). The electrocardiogram showed change in frontal axis from intrinsic conduction in only 2 (9 %) patients during tLVp and in 20 (87 %) patients during BiV pacing.

Conclusions: The acute effect of tLVp on LV systolic function and contraction pattern is significantly lower than the effect of BiV pacing and not different from intrinsic conduction in patients with LBBB and CRT.