Phrenic stimulation management in CRT patients: are we there yet?

Phrenic stimulation may hinder left-ventricular (LV) stimulation and prevent cardiac resynchronization therapy (CRT) delivery. We reviewed the literature to address its prevalence and clinical implications in CRT patients.

Phrenic stimulation prevalence ranges from 20 to 33% of patients when a posterolateral LV lead placement is aimed. False-negatives are common during implantation, sensitivity being about 60-80%. Symptoms may dictate repositioning the LV lead, meaning risk of lead dislodgement, decreased CRT efficacy, or high LV threshold. CRT turn-off occurred in 2% of patients because of refractory phrenic stimulation. Several strategies have been used to manage phrenic stimulation: whereas lead repositioning was the only one available in early CRT experience, the use of bipolar/multipolar leads combined with cathode programmability enabling several pacing configurations has made possible targeting the optimal LV pacing sites in nearly all patients.Despite technological improvements, phrenic stimulation symptoms are sporadically reported by 6-8% of patients at follow-up, meaning that there is still an unmet need to address this problem.

Phrenic stimulation needs to be carefully managed at implantation and follow-up. Use of bipolar/multipolar leads and of multiple pacing configurations is mandatory to increase the chances of managing phrenic stimulation. Active fixation LV leads, hopefully bipolar, could further increase the success rate.