Incidence, Risk Factors, and Outcome of Life-Threatening Ventricular Arrhythmias in Giant Cell Myocarditis.

BACKGROUND Ventricular tachyarrhythmias are characteristic of giant cell myocarditis, but their true incidence, predictors, and outcome are unknown. METHODS AND RESULTS Our work involved 51 patients with giant cell myocarditis (35 women) aged 52±12 years. Their medical records were reviewed for history, results of laboratory and imaging studies, and occurrence of serious cardiac events, including life-threatening ventricular tachyarrhythmias. Sudden cardiac death (fatal or aborted) was the primary end point of our analyses, whereas the composite of sudden cardiac death and ventricular tachycardia requiring treatment constituted the secondary end point. Giant cell myocarditis presented as nonfatal ventricular tachyarrhythmia in 10 patients and as a fatal cardiac arrest in 1 patient. Overall, 14 of 50 patients suffered a sudden cardiac death during follow-up, with a cumulative incidence of 22% at 1 year and 26% at 5 years from presentation. The composite incidence of sudden cardiac death or ventricular tachycardia was 41% at 1 year and 55% at 5 years. The incidence of arrhythmias was associated with high plasma concentrations of troponin-T and N-terminal brain natriuretic propeptide, as well as with moderate-to-severe fibrosis on myocardial biopsy and history of ventricular tachyarrhythmias at presentation (P<0.05 for all). An intracardiac cardioverter defibrillator was implanted in 31 patients, of whom 17 had altogether 114 appropriate antiarrhythmic therapies by the device and none suffered an arrhythmic death. CONCLUSIONS In giant cell myocarditis, the risk of life-threatening ventricular arrhythmias exceeds 50% at 5 years from admission, being related to the presenting clinical manifestation and markers of myocardial injury and scarring.