First, recurrent tachycardia less likely in women vs. men with primary prevention ICD
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Women with HF who received an implantable cardioverter defibrillator for primary prevention were less likely to experience first and recurrent life-threatening ventricular tachycardias compared with men, researchers reported.
“Prior studies of patients with an ICD have demonstrated conflicting results regarding the association of sex with the incidence of appropriate device therapy, overall mortality, and thus the benefit of prophylactic placement of ICDs in women with HF,” Shireen Saxena, BA, MD candidate in the Clinical Cardiovascular Research Center at the University of Rochester Medical Center, New York, and colleagues wrote in JAMA Network Open. “We aimed to evaluate the association between sex and the risk of first occurrence of sustained ventricular tachyarrhythmia, total ventricular tachyarrhythmia and shock burden during the follow-up period in a recurrent event analysis, and non-arrhythmic mortality among all patients with primary prevention ICD implantation who were enrolled in the landmark Multicenter Automatic Defibrillator Implantation Trials (MADIT).”
The MADIT trials
The MADIT trials evaluated outcomes of patients with ischemic cardiomyopathy, left ventricular ejection fraction less than 35% and ventricular tachycardia implanted with an ICD or cardiac resynchronization therapy defibrillator compared with no implant.
As Healio previously reported, CRT in patients with HF and ventricular tachycardia was associated with lower rates of ventricular arrhythmia events, sudden cardiac death and all-cause death over time compared with those without an ICD.
In the present analysis of the MADIT trials, researchers evaluated the sex differences in risk for mortality and ventricular tachycardia among 4,506 patients (mean age, 64 years; 76% men). The primary endpoint was sustained ventricular tachycardia, defined as ICD-recorded, treated or monitored ventricular tachycardia of at least 170 beats per minute or ventricular fibrillation. Secondary endpoints included ventricular tachycardia of at least 200 beats per minute, appropriate ICD shocks and appropriate anti-tachycardia pacing.
Within this cohort, both age and LVEF were similar between men and women; however, women experienced less nonischemic cardiomyopathy (42% vs. 74%).
Researchers observed that women had lower 3-year risk for sustained ventricular tachycardia (16% vs. 26%), fast ventricular tachycardia (9% vs. 17%) and appropriate ICD shocks (7% vs. 15%) compared with men (P for all < .001).
Women experienced an approximately 40% lower risk for all endpoints (P for all < .001), including the primary endpoint (HR for first event = 0.6; 95% CI, 0.5-0.73; P < .001; HR for recurrent event = 0.49; 95% CI, 0.43-0.55; P < .001), according to the study.
Saxena and colleagues reported that these findings were consistent in subgroup analysis and were more especially pronounced among women with nonischemic cardiomyopathy compared with men (HR for nonischemic = 0.5; 95% CI, 0.38-0.66; P < .001; HR for ischemic = 0.73; 95% CI, 0.56-0.95; P = .02; P for interaction between female sex and cardiomyopathy = .03).
“To our knowledge, this is the first study to examine sex differences in not only initial occurrence of ventricular tachyarrhythmia or first appropriate ICD therapy but also the overall burden of each of these endpoints among patients with primary prevention ICD implantation,” the researchers wrote. “More specifically, our findings depicted that women have approximately half the risk of recurrent ventricular tachyarrhythmia, or recurrent appropriate ICD shocks, compared with men, which was again more pronounced in nonischemic cardiomyopathy than in ischemic cardiomyopathy.”
Importance of sex-specific risk stratification
In a related editorial, Christian Sticherling, MD, deputy chief physician and head of electrophysiology in the department of cardiology, University Hospital of Basel, University of Basel, Switzerland, discussed how these findings highlight the importance of sex-specific risk stratification.
“How can the presented results be helpful in daily decision-making? It is unlikely that the specificity and negative predictive value of a single risk parameter ... will suffice to replace left ventricular ejection fraction as a risk marker in primary prevention. Composite risk scores such as the MADIT-ICD benefit score or the DERIVATE score are more likely to be of benefit,” Sticherling wrote. “The work by Saxena et al underlines once more that there are important differences in cardiovascular outcomes between men and women and that the underrepresentation of women in randomized controlled trials is a problem that needs to be taken into account.”
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