Myocarditis with arrhythmic presentation: clinical and prognostic insights from a large monocentric prospective cohort

Backgrounds and objectives: Myocarditis is an inflammatory disease of the myocardium characterized by highly heterogeneous clinical manifestations at onset. A proportion of patients present with arrhythmias as the primary or unique manifestation. At disease onset, some develop potentially fatal ventricular arrhythmias (VAs) necessitating implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT) implantation for protection against sudden cardiac death (SCD). Unlike other cardiac conditions, the short- and long-term arrhythmic burden in myocarditis remains incompletely characterized. Furthermore, few clinically available predictors, not validated in randomized trials, exist to stratify arrhythmic risk and guide device implantation decisions. Our study aims to better define evolution and current management of patients with arrhythmic myocarditis, find out clinical predictors of device implantation and device interventions in this population, and evaluate the efficacy of a wearable cardioverter defibrillator (WCD) as bridge to recovery tool, and as protection instrument against life-threatening VAs. Methods: We prospectively collect data of 111 patients with myocarditis presenting primarily with any type of arrhythmia, comparing clinical characteristics at baseline and over a median follow-up period of 4.4 years (53 months). Clinical characteristics, electrocardiographic and echocardiographic features, as well as cardiac magnetic resonance (CMR) and histology, Holter monitoring and device interrogation data were registered and analyzed. Diagnosis was confirmed via endomyocardial biopsy (EMB) in 58 patients (52%); the others fulfilled clinical and CMR criteria according to current guidelines. Coronary angiography, laboratory testing, echocardiography, and clinical evaluation were used to exclude alternative cardiac pathologies. Results: 45 out of 111 patients (41%) received an ICD/CRT during follow-up (71% primary prevention, 29% secondary prevention). 11 patients (10%) utilized a WCD to delay permanent implantation, but none received WCD intervention. Seven of them subsequently underwent device implantation, with one experiencing appropriate shock therapy. Despite extensive utilization of antiarrhythmic therapy, 20 out of 45 device pag. 7 recipients (44%) received at least one appropriate shock after a median time of 19 months. At multivariate analysis we identified male sex (OR 4.08, 95% CI 1.08–18.7, p=0.038) as a risk factor for device implantation, while higher EF ( OR 0.95, 95% CI 0.90-1.00, p=0.027) and advanced age (OR 0.94, 95% CI 0.90–0.99, p=0.008) exhibited a protective role. As general trend we observed a protective role against device implantation in patient positive for serum anti-heart autoantibodies (AHA) (OR0.33, 95% CI 0.09-1.05 p=0.061) Ventricular tachycardia (VT) at onset, predicted appropriate device intervention (OR 5.83, 95% CI 1.71–24.2, p=0.004). Conclusion: In our cohort of myocarditis patients a significant proportion require anti tachycardia devices as protection tool when arrhythmia is the main sign at presentation. Patients with arrhythmic myocarditis remain at risk of fatal arrhythmias beyond the acute phase, particularly those with severe initial presentation, supporting guideline recommendations for secondary-prevention devices. Male sex (OR 4.08) is a risk factor for anti-tachycardia device implantation, while advanced age (0.94) and higher EF (0.95) are protective factor. At multivariable analysis VT at disease onset is an independent risk factor for appropriate device intervention at long term follow up (5.83).