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Cardiac Resynchronization Therapy in Women: US Food and Drug Administration Meta-Analysis of Patient-Level Data
Study Questions:
Do women with left bundle branch block (LBBB) benefit from cardiac resynchronization therapy-defibrillators (CRT-Ds) at a shorter QRS duration than men with LBBB do?
Methods:
Individual patient data were pooled from three CRT-D versus implantable cardioverter-defibrillator (ICD) trials (4,076 patients) enrolling predominantly patients with New York Heart Association (NYHA) class II heart failure and follow-up to 3 years. The effect of CRT-D compared with ICD on outcomes was assessed using random-effects Cox proportional hazards.
Results:
Women benefited from CRT-D more than men. The main difference occurred in patients with LBBB and a QRS of 130-149 ms. In this group, women had a 76% reduction in heart failure or death (absolute CRT-D to ICD difference, 23%; hazard ratio [HR], 0.24; 95% confidence interval [CI], 0.11-0.53; p < 0.001) and a 76% reduction in death alone (absolute difference, 9%; HR, 0.24; 95% CI, 0.06-0.89; p = 0.03), while there was no significant benefit in men for heart failure or death (absolute difference, 4%; HR, 0.85; 95% CI, 0.60-1.21; p = 0.38) or death alone (absolute difference, 2%; HR, 0.86; 95% CI, 0.49-1.52; p = 0.60). Neither women nor men with LBBB benefited from CRT-D at a QRS shorter than 130 ms, whereas both sexes with LBBB benefited at a QRS of 150 ms or longer.
Conclusions:
In this population of patients with primarily mild heart failure, women with LBBB benefited from CRT-D at a shorter QRS duration than men with LBBB. This is important because recent guidelines limit the Class I indication for CRT-D to patients with LBBB and QRS of 150 ms or longer. While guidelines do give a Class IIa indication to patients with LBBB and a QRS of 120-149 ms, the present findings are important to communicate because women are less likely to receive a CRT-D than men. This study exemplifies the potential public health and regulatory science value of combining data from multiple clinical trials submitted to the Food and Drug Administration.
Perspective:
The current study lends support to the use of sex-specific criteria for LBBB. It has been suggested that men have a higher incidence of left ventricular hypertrophy with left anterior fascicular block masquerading as LBBB. Furthermore, because of potential sex-specific differences in outcomes, this study highlights the need for greater representation of women in clinical studies.
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