Maximization of interventricular conduction time by means of quadripolar leads for cardiac resynchronization therapy

Identifying the left ventricular (LV) site associated with the maximum spontaneous interventricular conduction time (right ventricle (RV)-to-LV interval) has proved to be an effective strategy for optimal LV pacing site selection in cardiac resynchronization therapy (CRT). The aim of our study was to determine whether quadripolar LV lead technology allows RV-to-LV interval maximization.

We enrolled 108 patients undergoing implantation of a CRT system using an LV quadripolar lead and 114 patients who received a bipolar lead. On implantation, the RV-to-LV interval was measured for the dipole of the bipolar leads and for each electrode of the LV lead (tip, ring 2, ring 3, ring 4).

In the quadripolar group, the mean RV-to-LV interval ranged from 90 ± 33 ms (tip) to 94 ± 32 ms (R4) (p > 0.05 for all comparisons). In 55 (51%) patients, the RV-to-LV interval was > 80 ms at all electrodes, while in 27 (25%) patients, no electrodes were associated with an RV-to-LV interval > 80 ms. At least one LV pacing electrode was associated with an RV-to-LV interval > 80 ms in 62 (70%) patients with a short (36 mm) inter-electrode distance, and in 19 (95%, p = 0.022) of those with a long distance (50.5 mm). In the bipolar group, the mean RV-to-LV interval was 72 ± 37 ms (p < 0.001 versus quadripolar). The RV-to-LV interval was > 80 ms in 44 (39%) patients (p < 0.001 versus quadripolar leads with both short and long inter-electrode distance).

Quadripolar leads allow RV-to-LV interval maximization. An optimal RV-to-LV interval seems achievable in the majority of patients, especially if the leads present a long inter-electrode distance.