PR-Interval Identifies Clinical Response in Patients with Non-LBBB: A MADIT-CRT Sub-Study
Background—In MADIT-CRT, patients with non-LBBB (including RBBB, IVCD) 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 in two 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 (HF) or death. Separate secondary end points included HF events and all-cause mortality. Cox proportional hazards regression models were used to compare risk of end point events by CRT-D to ICD 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 HF/Death (HR=0.27, 95% CI: 0.13-0.57, p<0.001) and 81% decrease in the risk of all-cause mortality (HR=0.19, 95% CI: 0.13-0.57, p<0.001) compared to ICD therapy. In non-LBBB patients with normal PR, CRT-D therapy was associated with a trend towards an increased risk of HF/Death (HR=1.45, 95% CI: 0.96-2.19, p=0.078, interaction p-value<0.001) and more than a 2-fold higher mortality (HR=2.14, 95% CI: 1.12-4.09, p=0.022, interaction p-value<0.001) compared to ICD 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.
Clinical Trial Registration—http://clinicaltrials.gov; Unique Identifier: NCT00180271
- cardiac resynchronization therapy
- implantable cardioverter-defibrillator
- heart failure
- atrioventricular block
- Received October 14, 2013.
- Revision received May 12, 2014.
- Accepted May 14, 2014.