Influence of pacing configurations, body mass index, and position of coronary sinus lead on frequency of phrenic nerve stimulation and pacing thresholds under cardiac resynchronization therapy.

AIMS: Phrenic nerve stimulation (PNS) can affect, and in some cases considerably limit, the long-term success of cardiac resynchronization therapy (CRT) therapy. To address this common problem, the manufacturers of CRT devices offer a range of configurations aimed at preventing high left ventricular pacing thresholds (LVPTs) and PNS. METHODS AND
RESULTS: In 101 consecutive patients who had undergone implantation of a CRT system, we investigated prospectively the parameters LVPT and PNS threshold in relation to coronary sinus (CS) lead position, CS lead configuration, body position, and body mass index. With the configurations LV tip to right ventricular (RV) coil, LV tip to LV ring, and LV ring to RV coil, the LVPT and PNS threshold of patients with LV pacing were measured in the supine and left lateral body positions. The overall mean LVPT was lowest in LV tip to RV coil and highest in LV ring to RV coil configurations. The lowest PNS thresholds were measured in LV tip to RV coil and the highest in LV tip to ring configurations. The LVPT was not affected by body position and was stable in the standard supine and left lateral positions.
CONCLUSION: Flexible LV pacing configurations are a useful feature of CRT systems for preventing PNS. The optimal LV pacing configuration should be determined on the basis of individual patient testing.