Ineffective Cardiac Resynchronization Pacing is Associated with Poor Outcomes in a Nationwide Cohort Analysis

Background Delivery of cardiac resynchronization therapy (CRT) requires left ventricular myocardial capture to achieve clinical benefits. Objective We sought to determine whether ineffective pacing impacts survival. Methods Ineffective ventricular pacing (VP) was defined as the difference between percent delivered CRT (%VP) and percent EffectivCRTTM in CRT devices. Using the Optum® de-identified Electronic Health Record dataset (Optum® EHR) and Medtronic CareLinkTM data warehouse, we identified patients implanted with applicable devices with at least 30 days follow-up. Kaplan-Meier and Cox proportional hazards models assessed the impact of %VP and % ineffective VP on survival. Results Among 7,987 patients with 2.1±1.0 years follow up, increasing ineffective VP was associated with decreasing survival: the highest observed survival was in the quartile with <0.08% ineffective VP and the lowest survival was in the quartile with >1.47% ineffective VP (85.1% vs. 75.7% at 3 years, p<0.001). As expected, patients with more than the median %VP of 97.7% had better survival than patients with <97.7% VP (84.2% vs. 77.8%, p < 0.001). However, patients that had >97.7% VP but >2% ineffective VP had similar survival to patients with <97.7% VP but ≤2% ineffective VP (81.6% vs 79.4%, p = 0.54). A multivariable Cox proportional hazards model demonstrated that <97.7% VP (adjusted HR 1.29; 95% CI 1.14-1.46; p <0.001) and >2% ineffective VP (HR 1.35; 95% CI 1.18-1.54; p<0.001) were both significantly associated with decreased survival. Conclusions Ineffective VP is associated with decreased survival. In addition to maximizing the percentage of delivered CRT pacing, every effort should be made to minimize ineffective VP.