Programmed ventricular stimulation in patients with active vs previous arrhythmic myocarditis

No studies so far addressed the role of invasive programmed ventricular stimulation (PVS) in myocarditis patient's arrhythmic risk stratification. Methods and Results We present a single‐center prospective study on 96 consecutive adult patients (44 ± 13 years, 70.1% males) with myocarditis and ventricular arrhythmias (VA) at index hospitalization. Depending on baseline endomyocardial biopsy (EMB) and cardiac magnetic resonance, patients were divided into two groups: active (A) vs nonactive (NA) myocarditis. All of the patients underwent PVS at index hospitalization. Medical treatment and implantable cardioverter‐defibrillator (ICD) implantation were clinically‐driven. Malignant VA episodes (MVA = ventricular tachycardias [VT], ventricular fibrillation [VF], appropriate ICD therapy) were evaluated at 54 ± 18 months follow‐up (FU). Patients who underwent VT ablation or with myocarditis recurrence (n = 9) were excluded. Of 87 patients, 41 (47.2%) were in group A. PVS was positive in 32 cases (36.8%), 16 A vs 16 NA ( P  = NS), with no associations with VA type at presentation. Before discharge, 55 patients (63.2%) underwent ICD implant. In FU, MVA occurred in 27 patients (31.0%), 13 A vs 14 NA ( P  = NS), 18 PVS+ vs 9 PVS‐ ( P  < .001). The association between PVS result and FU MVA was maximal in group NA (high rule‐out performance with negative predictive value = 90.0%, P  < .001) and minimal in group A (low rule‐in performance with PPV = 43.8%, P  = .302). In the whole population, three independent factors for major VA were identified: major arrhythmic onset by sustained VT or VF (HR 2.8, 95% CI, 1.0‐7.4, P  = .042), presence of fibrosis at EMB (HR 5.8, 95% CI, 1.1‐30.0, P  = .038), and PVS positivity (HR 4.2, 95% CI, 1.7‐10.7, P  = .003). Conclusion In myocarditis patients presenting with VA, PVS is associated with FU MVA in NA patients, but not in A ones. Overall, risk stratification of arrhythmic myocardits is still complex and multifactorial.