Cardiac Resynchronization Therapy in Ischemic Versus Nonischemic Cardiomyopathy: Patient-Level Meta-Analysis of 7 Randomized Clinical Trials

Background: Data on whether cardiac resynchronization therapy (CRT) results in better clinical and echocardiographic outcomes in patients with nonischemic cardiomyopathy (NICM) vs ischemic cardiomyopathy (ICM) are conflicting.

Objectives: The authors conducted this meta-analysis of 7 clinical trials of CRT to determine the association between etiology of cardiomyopathy and clinical and echocardiographic outcomes.

Methods: The authors analyzed patient-level data using Bayesian Hierarchical Weibull survival regression modeling to determine the association between etiology of cardiomyopathy and time to all-cause death or heart failure hospitalization (HFH). Linear regression was used to assess the association between etiology of cardiomyopathy and echocardiographic measurements.

Results: Of 6,252 patients included, 4,717 (75%) were men, median age was 66 years (IQR: 58-73 years), 3,704 (59%) had ICM, and 3,778 (60%) received CRT. CRT increased the time to HFH or all-cause death (HR: 0.67; 95% credible interval [CrI]: 0.56-0.82; P < 0.001) with no difference by etiology of cardiomyopathy (HR ratio: 1.06 [95% CrI: 0.87-1.29]; P = 0.57). Likewise, CRT increased the time to all-cause death (HR: 0.71 [95% CrI: 0.55-0.93]; P = 0.019) with no difference by etiology of cardiomyopathy (HR ratio: 1.06 [95% CrI: 0.80-1.43]; P = 0.70). Echocardiographic data that were available for 2,430 (39%) patients showed that CRT improvements in left ventricular ejection fraction, left ventricular end-diastolic diameter, and left ventricular end-systolic diameter were larger for patients with NICM.

Conclusions: Although CRT led to greater increases in left ventricular ejection fraction and reductions in ventricular dimensions for patients with NICM compared with those with ICM, CRT significantly increased the time to HFH or all-cause death independently of the etiology of cardiomyopathy. Further studies on improving patient selection for CRT are needed.