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Study Summary

Internal cardiac defibrillators have been shown to be effective at preventing arrhythmic sudden cardiac death (SCD) in patients with a history of myocardial infarction (MI) and reduced ejection fraction (EF); however, trials in the early post-MI period have been negative. The use of wearable cardiac defibrillators (WCDs) was evaluated in a multicenter, randomized trial in patients with an MI and EF <35% within 7 days of their hospital discharge. In total, 1524 patients were randomized to receive a WCD + goal-directed medical therapy, with 778 patients assigned to medical therapy alone (controls). Baseline characteristics were similar between groups. Those assigned to the WCD group wore their device for an average of 14.1 hours per day. In an intention-to-treat analysis at 3 months follow-up, 1.6% in the WCD arm and 2.4% of controls had experienced SCD (P = 0.18) (see accompanying Hurst’s Central Illustration). In the WCD group, the any-case death rate was significantly decreased (3.1% vs. 4.9% in the control arm; P = .04), and <1.4% of patients received an appropriate therapy.

Wearable Cardiac Defibrillators in the Early Post-MI Period

Commentary

Study Strengths: For over the past decade, the WCD has been used clinically in patients who are early post-MI with reduced EF. This trial represents the only randomized trial to date that examines the efficacy of the WCD in the prevention of SCD. In this trial, patients in both arms received high rates of contemporary goal directed medical therapy. The low event and mortality rates in this study support the impact of contemporary post–MI therapies.

Study Limitations: This study was not blinded, and compliance was low overall in the WCD arm with patients wearing their devices for a mean of 14.1 hours per day. Furthermore, there were low rates of the primary endpoint with only 25/1524 patients in the WCD arm and 19/778 in the control arm reaching the endpoint of SCD. These low event and mortality rates in this study support the impact of contemporary post–MI therapies. Unexpectedly, more patients in the control arm experienced stroke related deaths which contributed to the mortality advantage in the WCD group.

Next Steps/Clinical Perspective: Although concerns such as low event rates, limited compliance and possible misclassification of SCD may explain the lack of reduction in the primary endpoint, this trial should be interpreted as having failed to reduce SCD. While this study included all patients with decreased EF in the post MI period, further investigation may better identify a higher-risk subset that may benefit from interim use of a WCD. This along with a cost-effectiveness analysis will be needed to determine its role in this population.

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