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

Idiopathic giant cell myocarditis (GCM) is a rare but serious heart muscle disease whose pathogenesis is insufficiently known but commonly attributed to T cell–mediated autoimmunity. The early international registry studies of the 1990s characterized GCM as a disease that mainly involves young and middle-aged individuals and is deadly to the extent that 50% of the diseased either die or undergo transplant surgery in <6 months and only 10% are alive at 5 years from symptom onset without a cardiac transplant. Later studies have shown, however, that the true spectrum of GCM is more wide and may even encompass years of indolent course, as well as transplant-free survivals that approach 90% in 1 year and can extend ≤20 years in some individuals. Although progressive heart failure is the best known manifestation of GCM and the leading cause of cardiac transplantation, life-threatening ventricular arrhythmias are not uncommon either. In the above registry studies, ventricular tachyarrhythmia was the second most common presenting manifestation and refractory ventricular tachycardia (VT) developed in almost half of the patients during follow-up. Fatal arrhythmia is also a common mechanism of cardiac death in GCM. For all that, except for a small earlier patient series from our hospital, there exists no in-depth research on ventricular arrhythmias in GCM. We have included all GCM patients seen at our institution since 1991 in a cumulative registry study that currently goes on prospectively. Our latest publication focused on transplant-free survival in GCM and showed that patients receiving immunosuppressive treatment had a 48% 5-year survival, with markers of myocardial injury being predictive of outcome. Because as many as four fifths of cardiac deaths appeared to have an arrhythmic mechanism, we set out to analyze in detail the occurrence of life-threatening ventricular arrhythmias in GCM. Here we describe their incidence and risk factors, as well as observations on their outcome with treatment, in consecutive GCM patients seen at our hospital over the last 25 years.