Elimination of phrenic nerve stimulation occurring during CRT: follow-up in patients implanted with a novel quadripolar pacing lead.

Background: Phrenic nerve stimulation (PNS) occurs at follow-up in approximately 20% of patients with bipolar leads. The quadripolar Quartet model 1458Q (St. Jude Medical, Sylmar, CA, USA) left ventricular lead (LV) has four electrodes (one distal tip and three ring) capable of ten different pacing vectors which may allow reprogramming to eliminate PNS.

Methods: Forty patients underwent attempted CRT-D implantation between October 2009 and October 2010 with the Quartet lead. Pacing parameters, lead position, complications and presence of PNS were collected at implant, pre-discharge and at 3 and 6 months follow-up.

Results: A quadripolar LV lead was successfully implanted in 95% (38/40) of patients. During follow-up, one patient (3%) had a lead displacement requiring reposition. LV pacing parameters remained stable at 6 months follow-up (mean threshold 1.3 V at 0.6 ms and impedance 948 Ω). PNS at the time of implant was observed in 12 patients (32%) all of which were overcome by using the additional vectors available on the quadripolar LV lead or by repositioning the lead at the time of index implant. During 6 months follow-up there were five (13%) cases of PNS, all of which were successfully treated by reprogramming to a different vector. No cases required reintervention, surgical epicardial lead placement, or that lead be turned off.

Conclusion: The quadripolar Quartet lead is associated with a high implant success rate, stable pacing parameters and a low displacement rate during the first 6 months after implant. The ten LV pacing vectors available with this lead allowed PNS and capture threshold problems to be overcome at implant, and importantly at follow-up, thus obviating the need for lead reposition.