Heart Substructure Radiation Dose and Cardiac Outcomes: Contemporary Evidence and Actionable Opportunities: JACC CardioOncology State-of-the-Art Review.

Contemporary cardiac outcomes research demonstrates that radiation dose to discrete cardiac substructures, particularly the coronary arteries, left ventricle, and pulmonary veins, strongly predict ischemia, heart failure, and arrhythmia endpoints, respectively, compared to whole heart metrics. This rapidly expanding literature has produced an increasingly rich but heterogeneous evidence base, underscoring both substantial progress and a persistent gap in clinical implementation. Importantly, current cardio-oncology guidelines and expert panel statements offer comprehensive cardiovascular recommendations, but integration of cardiac radiation dose exposure thresholds that translate into actionable clinical guidance remains limited. This partial alignment between emerging evidence and formal guidance contributes to uncertainty in clinical adoption and is further compounded by workflow complexity, limited consensus, and sparse clinical trial integration. In this State-of-the-Art Review, we synthesize contemporary cardiac dosimetry evidence on cardiac outcomes, propose a pragmatic, clinically-oriented framework, and outline actionable strategies to shorten the evidence-to-practice gap in the modern radiotherapy care continuum.