A major trial found that implantable cardioverter-defibrillators may benefit some patients younger than 70 with mild-to-moderate heart dysfunction and cardiac scarring. A more than decade-long randomized trial suggests that implantable cardioverter-defibrillators may benefit some patients who have heart scarring and only mild-to-moderate loss of heart function, a group that currently falls outside standard treatment guidelines. […]This is a curated summary.