The importance of early evaluation after cardiac resynchronization therapy to redefine response: Pooled individual patient analysis from 5 prospective studies.

Background: Cardiac resynchronization therapy (CRT) reduces mortality and improves outcomes in appropriately selected patients with heart failure (HF); however, response may vary.

Objective: We sought to correlate 6-month CRT response assessed by clinical composite score (CCS) and left ventricular end-systolic volume index (LVESVi) with longer-term mortality and HF-related hospitalizations.

Methods: Individual patient data from 5 prospective CRT studies-Multicenter InSync Randomized Clinical Evaluation (MIRACLE), Multicenter InSync ICD Randomized Clinical Evaluation (MIRACLE ICD), InSync III Marquis, predictors of response to cardiac resynchronization therapy (PROSPECT), and Adaptive CRT-were pooled. Classification of CRT response status using CCS and LVESVi were made at 6 months. Kaplan-Meier analyses were used to assess time to mortality. Cox proportional hazards regression models were used to compute hazard ratios (HRs) for the 3 levels of CRT response: improved, stabilized, and worsened. Adjusted models controlled for baseline factors known to influence both CRT response and mortality. HF-related hospitalization was compared between CRT response categories using incidence rate ratios.

Results: Among a total of 1603 patients, 1426 and 1165 were evaluated in the CCS and LVESVi outcome assessments, respectively. Mortality was significantly lower for patients in the improved (CCS: HR 0.22; 95% confidence interval [CI] 0.15-0.31; LVESVi: HR 0.40; 95% CI 0.27-0.60) and stabilized (CCS: HR 0.38; 95% CI 0.24-0.61; LVESVi: HR 0.41; 95% CI 0.25-0.68) groups than in the worsened group for both measures after adjusting for potential confounders.

Conclusion: Patients with a worsened CRT response status have a high mortality rate and HF-related hospitalizations. Stabilized patients have a more favorable prognosis than do worsened patients and thus should not be considered CRT nonresponders.