Limitations of chronic delivery of multi-vein left ventricular stimulation for cardiac resynchronization therapy

Abstract

Dual-site epicardial left ventricular (LV) pacing represents one strategy to improve acute cardiac resynchronization therapy (CRT) response. However, the feasibility of this approach in the longer term may be hindered by system complexity. We assessed chronic outcomes of patients receiving dual-site LV pacing. Twenty patients with conventional CRT criteria were implanted with dual-site epicardial LV leads connected with bifurcating adapter. Mean energy required to capture the LV was calculated using threshold, impedance and pulse width. Values were obtained during implant and the following day. Follow-up data included lead parameters, ventricular arrhythmias and mortality. Nineteen patients had successful dual LV lead placement. Mean age was 66 ± 11 years, mean left ventricular ejection fraction (LVEF) 26% ± 8 and 50% ischemic etiology. Mean energy to capture the LV was 1.95 μJ for LV1 during implant, rising to 8.61 μJ at day 1, p = 0.03. The energy required for LV2 was 2.37 μJ during implant, 11.55 μJ the next day, p = 0.004. Eleven percent had LV2 turned off during the implant due to high thresholds and/or a worsened acute hemodynamic response. Eleven percent had LV2 turned off day 1 post implant due to inability to capture LV2 at maximum output. All remaining 15 patients had LV2 programmed off, with a mean time of 255 days from implant. Thirty-two percent of patients received ATP or shock, and sixteen percent died over a mean follow-up of 1271 days. Thirty-seven percent of patients required generator replacement with mean longevity of 42 months, far shorter than the suggested lifespan of the device (58 months), p = 0.006. Multisite epicardial LV lead placement may be acutely feasible and demonstrate beneficial hemodynamic results at implantation. Long-term delivery of this therapy is however problematic due to technical issues with pacing through the bifurcating adapter. This suggests the feasibility of this form of multisite CRT is limited.