The clinical implications of cumulative right ventricular pacing in the multicenter automatic defibrillator trial II.
BACKGROUND
This study was designed to assess whether right ventricular pacing in the implantable cardioverter defibrillator (ICD) arm of the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II was associated with an unfavorable outcome.


RESULTS
Data on the number of ventricular paced beats were available in 567 (76%) of 742 MADIT II patients with ICDs. The number of ventricular paced beats over the total number of beats showed a bimodal distribution with patients being predominantly paced or nonpaced. Therefore, patients were dichotomized at 0-50% and 51-100% of cumulative pacing with median pacing rate 0.2% and 95.6%, respectively. Endpoints included new or worsening heart failure, appropriate ICD therapy for VT/VF, and the combined endpoint of heart failure or death. Clinical features associated with frequent ventricular pacing included age >or=65 years, advanced NYHA heart failure class, LVEF < 0.25, first degree AV and bundle branch block, and amiodarone use. During follow-up, 119 patients (21%) had new or worsened heart failure, 130 (23%) had new or worsened heart failure or death, and 142 (25%) had appropriate therapy for VT/VF. In comparison to patients with infrequent pacing, those with frequent pacing had significantly higher risk of new or worsened heart failure (hazard ratio = 1.93; P = 0.002) and VT/VF requiring ICD therapy (HR = 1.50; P = 0.02).


CONCLUSIONS
Patients in MADIT II who were predominantly paced had a higher rate of new or worsened heart failure and were more likely to receive therapy for VT/VF. These results suggest the deleterious consequences of RV pacing, particularly in the setting of severe LV dysfunction.
Steinberg
Jonathan S
JS
Division of Cardiology, St. Luke's-Roosevelt Hospital Center and Columbia University College of Physicians and Surgeons, New York, New York 10025, USA. jss7@columbia.edu
Fischer
Avi
A
Wang
Paul
P
Schuger
Claudio
C
Daubert
James
J
McNitt
Scott
S
Andrews
Mark
M
Brown
Mary
M
Hall
W Jackson
WJ
Zareba
Wojciech
W
Moss
Arthur J
AJ
D000368:Aged; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000295:instrumentation*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D008297:Male; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome; D016278:Ventricular Function, Right / Q000502:physiology*