Phrenic stimulation: a challenge for cardiac resynchronization therapy.
BACKGROUND
Phrenic stimulation (PS) may hinder left ventricular (LV) pacing. We prospectively observed its prevalence in consecutive patients with cardiac resynchronization therapy (CRT) devices.


RESULTS
In the years 2003 to 2006, 197 patients received a CRT device. PS and LV threshold measurements were carried out at implantation and at 6-month follow-up. LV reverse remodeling was assessed by echocardiography before implantation and at follow-up. LV lead placement was lateral/posterolateral in 86% of patients. Both PS and LV reverse remodeling occurred most frequently at the lateral/posterolateral LV pacing sites (P<0.001). PS was detected in 73 (37%) of patients and was clinically relevant in 41 (22%). The detection of PS at implantation had a poor sensitivity, as it occurred only in left lateral or sitting position in 27 patients. Ten patients (5%) underwent repeated surgery and 4 (2%) had their CRT turned off because of PS. At follow-up, we could manage PS noninvasively in 32 patients with a small PS-LV threshold difference: in 20 by cathode programmability (3 also thanks to automatic management of LV output) and in 12 (without cathode programmability) by programming the LV output as threshold +1 V.


CONCLUSIONS
PS may seriously hinder CRT. A bipolar LV lead and cathode programmability are mandatory to avoid PS by changing the LV pacing vector at target sites for CRT. LV stability at target sites despite PS should also be pursued by these means. The automatic adjustment of LV pacing output is complementary in patients with a small PS-LV threshold difference.
Biffi
Mauro
M
Institute of Cardiology, Policlinico S. Orsola-Malpighi, University of Bologna, Italy.
Moschini
Carlotta
C
Bertini
Matteo
M
Saporito
Davide
D
Ziacchi
Matteo
M
Diemberger
Igor
I
Valzania
Cinzia
C
Domenichini
Giulia
G
Cervi
Elena
E
Martignani
Cristian
C
Sangiorgi
Diego
D
Branzi
Angelo
A
Boriani
Giuseppe
G
D000368:Aged; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects* / Q000379:methods / Q000706:statistics & numerical data; D004452:Echocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010791:Phrenic Nerve / Q000503:physiopathology*; D011237:Predictive Value of Tests; D015995:Prevalence; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000209:etiology*