Implanted Defibrillators Did Not Cut the Combined Cardiac Risk, a JAMA Trial Reports

Patients with heart scarring and moderately reduced pumping function got no overall benefit from an implanted defibrillator, according to the CMR GUIDE trial published in JAMA on Aug. 28.

The trial's primary outcome was sudden cardiac death or a hemodynamically significant ventricular arrhythmia, a rhythm disturbance that drops blood pressure. It occurred in 14 patients (7.8%) who received a defibrillator and in 16 (9.2%) who received a monitoring device, the investigators report. The trial did not meet its primary endpoint, and implantation "did not reduce the composite outcome," the authors conclude.

CMR GUIDE randomized 353 patients at 18 sites in Australia, Germany and the United Kingdom: 180 to a primary-prevention implantable cardioverter-defibrillator and 173 to an implantable loop recorder, a device that records heart rhythm without treating it. All had ischemic or nonischemic cardiomyopathy, a left ventricular ejection fraction of 36% to 50%, and myocardial scar visible on a cardiac MRI scan. Median follow-up was 6.3 years, the paper states.

The two halves of the composite moved in opposite directions. Sudden cardiac death occurred in 3 defibrillator patients (1.7%) and 10 monitored patients (5.8%), while significant arrhythmia occurred in 12 (6.7%) and 6 (3.5%).

In a prespecified subgroup analysis, the investigators report, the primary outcome was less frequent with a defibrillator among patients younger than 70 (3.3% versus 10.0%) and more frequent among those 70 and older (16.9% versus 7.5%).

Current guidelines recommend a primary-prevention defibrillator at an ejection fraction of 35% or below, and CMR GUIDE was built to test the group above that line. The trial enrolled from 2015 to 2022 and was presented at the European Society of Cardiology Congress in Munich.