PR Interval Identifies Clinical Response in Patients With Non–Left Bundle Branch Block A Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy Substudy
Valentina Kutyifa, MD, PhD*; Martin Stockburger, MD*; James P. Daubert, MD; Fredrik Holmqvist, MD, PhD; Brian Olshansky, MD; Claudio Schuger, MD; Helmut Klein, MD; Ilan Goldenberg, MD; Andrew Brenyo, MD; Scott McNitt, MS; Bela Merkely, MD, PhD; Wojciech Zareba, MD, PhD; Arthur J. Moss, MD
Background—In Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy (MADITCRT),
patients with non–left bundle branch block (LBBB; including right bundle branch block, intraventricular conduction
delay) did not have clinical benefit from cardiac resynchronization therapy with defibrillator (CRT-D). We hypothesized
that baseline PR interval modulates clinical response to CRT-D therapy in patients with non-LBBB.
Methods and Results—Non-LBBB patients (n=537; 30%) were divided into 2 groups based on their baseline PR interval
as normal (including minimally prolonged) PR (PR <230 ms) and prolonged PR (PR ≥230 ms). The primary end
point was heart failure or death. Separate secondary end points included heart failure events and all-cause mortality.
Cox proportional hazards regression models were used to compare risk of end point events by CRT-D to implantable
cardioverter defibrillator therapy in the PR subgroups. There were 96 patients (22%) with a prolonged PR and 438 patients
(78%) with a normal PR interval. In non-LBBB patients with a prolonged PR interval, CRT-D treatment was associated
with a 73% reduction in the risk of heart failure/death (hazard ratio, 0.27; 95% confidence interval, 0.13–0.57; P<0.001)
and 81% decrease in the risk of all-cause mortality (hazard ratio, 0.19; 95% confidence interval, 0.13–0.57; P<0.001)
compared with implantable cardioverter defibrillator therapy. In non-LBBB patients with normal PR, CRT-D therapy
was associated with a trend toward an increased risk of heart failure/death (hazard ratio, 1.45; 95% confidence interval,
0.96–2.19; P=0.078; interaction P<0.001) and a more than 2-fold higher mortality (hazard ratio, 2.14; 95% confidence
interval, 1.12–4.09; P=0.022; interaction P<0.001) compared with implantable cardioverter defibrillator therapy.
Conclusions—The data support the use of CRT-D in MADIT-CRT non-LBBB patients with a prolonged PR interval. In
non-LBBB patients with a normal PR interval, implantation of a CRT-D may be deleterious.
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