Cardiac magnetic resonance for risk stratification of sudden cardiac death

Despite substantial therapeutic advances in the prevention and treatment of ICM and chronic HF, the burden of SCD remains a global health issue. In clinical practice the primary prevention of SCD is largely based on the identification of severe left ventricular systolic dysfunction by measurement of left ventricular ejection fraction in both ischemic or and non-ischemic heart disease. However, based on this criterion only 10% of primary prophylactic ICD implantations are delivering life-saving therapy, exposing the remaining 90% to all of the risks of ICD implantation and therapy without benefit. CMR is a non-invasive and radiation-free technique able to detect changes in biventricular volumes and function predictive of malignant ventricular arrhtmias and SCD. Of note, CMR offers the unique opportunity of myocardial tissue characterization and the advantage of accurate and reliable detection of arrhythmogenic morphological substrate in both ICM and NICM. LGE is a very established technique to image myocardial fibrosis and a robust predictor of adverse outcome in both ICM and NICM. Nowadays, a growing body of evidence demonstrates LGE imaging could substantially improve patient selection for ICD therapy by providing excellent visualization and characterization of the arrhythmic substrate. Further, the presence of myocardial edema on T2-weighted imaging has been associated with more advanced disease and increased arrhythmic burden in patients with hypertrophic cardiomyopathy. Finally, the development and validation of parametric mapping techniques for the quantification of myocardial edema and diffuse interstitial fibrosis will certainly help improve risk assessment of SCD in the next few years.