In this episode of The Lead, host Jason T. Jacobson, MD, FHRS, is joined by Sei Iwai, MD, FHRS, and Jeanne E. Poole, MD, FHRS, CCDS, to discuss “Cardiovascular Magnetic Resonance to Guide Defibrillator Implantation for LVEF of 36% to 50%: The CMR GUIDE Randomized Clinical Trial.” The panel examines the trial’s findings on using cardiovascular magnetic resonance–identified myocardial scar to guide primary prevention ICD implantation, including limitations of the study and current approaches to sudden cardiac death risk stratification, as well as the potential role of more sophisticated, dynamic risk-prediction models.