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Evidence failed to show mortality differences linked to ICDs in patient subgroups
In a new meta-analysis that examined the effectiveness of implantable cardioverter defibrillators for primary prevention of sudden cardiac death, evidence showed no differences for all-cause mortality in subgroups of patients based on age, sex and QRS interval.
Previous systematic reviews of ICDs for primary prevention suggested that ICDs may be less effective in women and elderly patients, according to background information in the study.
Based on the new analysis, “weak evidence fails to show differences for all-cause mortality in subgroups of sex, age and QRS interval,” researchers wrote. “Evidence is indeterminate for all-cause mortality in other subgroups and for [sudden cardiac death].”
The review included 14 studies collected from Medline and the Cochrane Central Register of Controlled Trials from inception through September 2013. Those evaluated included 10 randomized controlled trials and four longitudinal, nonrandomized, comparative studies. All studies contained data on the efficacy of ICDs for primary prevention of sudden cardiac death, and compared ICD vs. no ICD. Researchers examined ICD effectiveness across subgroups by age, sex, NYHA class, left ventricular ejection fraction, HF, left bundle branch block, QRS interval, time since MI, blood urea nitrogen level and diabetes, according to the study.
Meta-analysis of all 14 studies revealed a reduction in all-cause mortality with ICD treatment. Risk for all-cause mortality was reduced by approximately 31% in the 3 to 7 years after ICD implantation for patients without recent MI or coronary revascularization.
Ten studies yielded subgroup analysis. Nine studies compared ICD vs. no ICD, and one compared cardiac resynchronization therapy plus a defibrillator vs. no ICD. In these studies, the researchers found no significant difference in all-cause mortality according to age (≥65 years vs. <65 years), sex, QRS interval (≥120 ms vs. <120 ms) and the other subgroups examined. One exception was a study that found that ICDs were significantly more effective in patients with NYHA class II HF vs. class III.
The researchers said evidence yielded from the studies was “weak,” and conclusions could not be drawn for other evaluated subgroups due to a lack of data.
Of the studies included in the review, seven randomized studies and two nonrandomized studies indicated evidence of a significant benefit of ICDs for the reduction of sudden cardiac death. ICDs used for primary prevention were associated with a 63% reduction in risk for sudden cardiac death in the 2 to 6 years after implantation among patients with ischemic/nonischemic cardiomyopathy and no recent MI or concurrent coronary revascularization. Two of these studies included subgroup analyses; however, the researchers said those data were insufficient to assess the effects of ICDs on sudden cardiac death in subgroups.
“Our findings differ from conclusions by others who proposed differential effects by age and sex,” the researchers wrote.
“[ICD] therapy for primary prevention of [sudden cardiac death] vs. no ICD therapy shows benefit with regard to mortality and [sudden cardiac death]. … Further exploration of treatment heterogeneity to identify groups of patients who may particularly benefit (or derive no benefit) from ICD use are needed, especially when the cause of the disease, pathophysiology and competing risks for death differ. … A patient-level meta-analysis across major trials may be able to provide greater power to further evaluate subgroups.”
Disclosure: See the full study for a list of the researchers’ relevant financial disclosures.