JAMA Trial Finds ICDs Reduce Sudden Death in Younger Patients With LVEF 36-50% and Myocardial Scar

The trial tested ICD placement against standard care in patients with mild-to-moderate systolic dysfunction and late gadolinium enhancement on CMR. Primary endpoint was sudden cardiac death or sustained ventricular arrhythmia; secondary endpoint was sudden cardiac death alone. Overall primary endpoint showed no statistical significance, yet the prespecified age-stratified analysis demonstrated benefit below age 70, while the secondary endpoint favored ICDs across the full cohort. This design directly addresses a guideline gap where most sudden deaths occur in patients outside the LVEF ≤35% threshold.

Prior observational cohorts and the DANISH trial already hinted that scar burden, not ejection fraction alone, drives arrhythmic risk. The current findings extend that logic but expose the absence of absolute risk reductions, number-needed-to-treat, and competing non-arrhythmic mortality data. Younger patients likely derive greater net benefit because non-cardiac death rates are lower, yet the trial did not report interaction p-values or subgroup event rates, limiting immediate translation.

Guideline committees will require at least one confirmatory RCT powered for all-cause mortality and cost-effectiveness before changing class I recommendations. Ongoing registries that combine CMR scar quantification with wearable defibrillator data could supply the missing absolute risks within two years.

Next, investigators must publish full Kaplan-Meier curves, subgroup hazard ratios, and device-related complication rates to allow individualized decisions.