Sudden cardiac death in patients with myocarditis: Evaluation, risk stratification, and management

Myocarditis is a major cause of sudden cardiac death (SCD) and dilated cardiomyopathy (DCM) in young adults. Cardiac magnetic resonance is the established tool for the diagnosis of myocarditis, and late gadolinium enhancement detected on cardiac magnetic resonance imaging is the strongest independent predictor of SCD, all-cause mortality, and cardiac mortality. Several other factors have been associated with SCD or cardiac transplantation including New York Heart Association functional class III/IV, reduced left ventricular ejection fraction <35%, and right ventricular ejection fraction ≤45%. A fragmented QRS and a prolonged QTc interval on an electrocardiogram are predictors of VAs. The postulated mechanism of VA in acute myocarditis is ion channel dysfunction and inflammation that alter intracellular signaling, producing interstitial edema and fibrosis and thereby causing conduction abnormalities. VAs in chronic myocarditis are generally due to scar-mediated reentry. Treatment of myocarditis is tailored toward supportive care and symptomatic relief. The subset of patients who develop DCM should be treated with heart failure medications according to professional guideline recommendations. Indications for an implantable cardioverter-defibrillator are similar to those for nonischemic cardiomyopathy; however, an implantable cardioverter-defibrillator should be held in the acute phase of myocarditis to allow left ventricular ejection fraction recovery, and a wearable cardioverter-defibrillator may be beneficial for some patients. Antiarrhythmic medications are reserved for patients with symptomatic nonsustained or sustained VAs. Radiofrequency ablation appears to be an effective treatment option for VAs; however, more data on its safety and effectiveness are needed. This review addresses risk factors of SCD and VAs in patients with myocarditis with special emphasis on treatment and prevention of these outcomes.