Effect of Gender on Outcomes After Cardiac Resynchronization Therapy in Patients With a Narrow QRS Complex: A Subgroup Analysis of the EchoCRT Trial

Background—In EchoCRT, a randomized controlled trial evaluating the effect of cardiac resynchronization therapy (CRT) in patients with a QRS duration of <130 ms and echocardiographic evidence of left ventricular dyssynchrony, the primary outcome (death from any cause or first hospitalization for worsening heart failure) occurred more frequently in the CRT-ON when compared with the control group. In this prespecified subgroup analysis, we evaluated the effect of sex on clinical outcome in EchoCRT. Methods and Results—In EchoCRT, 585 (72%) of included patients were men. At baseline, male patients had a higher incidence of ischemic cardiomyopathy and longer QRS duration. On uni- and multivariable analysis, no significant interaction was observed regarding sex for the primary or any of the secondary end points. Numerically, a higher all-cause mortality was observed in male patients randomized to CRT-ON versus CRT-OFF on univariable analysis (hazard ratio, 1.83; 95% confidence interval, 1.08–3.12); however, no statistically significant interaction compared with females randomized to CRT-ON versus CRT-OFF was noted (hazard ratio, 0.99; P interaction, 0.56). There was no difference in the primary safety end point of system-related complications, including CRT system- and implantation-related events. Conclusions—The largest hazard for all-cause mortality in EchoCRT was observed in men randomized to CRT-ON; the comparison with women did not reach statistical significance, which may be because of the premature termination of the trial and the limited data. These results suggest that male sex may be a risk factor for harm by CRT in patients with narrow QRS width, an observation which deserves further investigation. Clinical Trial Registration—URL: https://clinicaltrials.gov. Unique identifier: NCT00683696.