Bifocal left ventricular stimulation or the optimal left ventricular stimulation site in cardiac resynchronization...

Several implantation strategies have been proposed to improve response to cardiac resynchronization therapy (CRT), including bifocal left ventricular (LV) stimulation and optimal single-LV lead placement. This study aimed to compare these two strategies during invasive pressure-volume (PV) loop measurements.

Thirty-three patients eligible for CRT were included [21 (64%) men, 20 (61%) ischaemic aetiology, QRS 155 ± 23 ms], and underwent cardiac magnetic resonance (CMR) imaging and invasive PV loop measurements. Left ventricular pump function was characterized by stroke work (SW) and dP/dtmax (5.1 ± 3.4 L mmHg and 856 ± 190 mmHg/s, respectively). Haemodynamic response was assessed during stimulation at single-LV sites and during bifocal LV [anterolateral and posterolateral (PL)] stimulation. Response during bifocal LV stimulation was not significantly higher compared with standard PL pacing (SW; β = 9.4 ± 5.4, P = 0.080; dP/dtmax, β = 0.2 ± 1.9, P = 0.922). However, mean pump function improvement was significantly higher during stimulation at the optimal LV site compared with bifocal LV stimulation (SW; β = 12.7 ± 5.1, P = 0.012; dP/dtmax, β = 3.3 ± 1.2, P = 0.020). Myocardial tissue properties were assessed by CMR tissue tagging. Mechanical activation at the optimal LV site was significantly more delayed compared with the worst LV site (431 ± 93 ms vs. 326 ± 127 ms; P = 0.004).

Stimulation at the optimal LV site showed a significantly higher pump function improvement compared with bifocal LV stimulation. Mechanical activation at the optimal LV site was significantly more delayed compared with the non-optimal LV site. In general, these results suggest that implantation of a second LV lead yields no additional benefit over implantation of one optimally placed LV lead. However, a bifocal approach might be beneficial in the individual patient.