Background: Data on long-term follow-up in patients (pts) with biopsy-proven myocarditis are conflicting, particularly those regarding ventricular events.
Purpose: To determine the prognostic variables for ventricular arrhythmias (VA) in pts with biopsy-proven myocarditis.
Methods: We prospectively studied consecutive pts with endomyocardial biopsy (EBM)-proven myocarditis (M1 Group). Control group was represented by pts presenting with suspected myocarditis, without EBM evidence of myocarditis (M0 Group). All pts underwent cardiac magnetic resonance imaging (MRI), coronary angiography, electrophysiological study (EPS) and electroanatomic mapping (EAM). Implantable cardioverter defibrillator or loop recorder was implanted in a subgroup of pts, following guidelines. The primary endpoint was the occurrence of sustained VA at follow-up (FU).
Results: 49 pts with biopsy-proven myocarditis were enrolled in Group M1, and 10 patients in Group M0 (mean age 41±15 vs 42±13 years respectively, p=0.87; men 59% vs 70% respectively, p=0.52). There were no statistically significant differences between the 2 groups regarding clinical variables and imaging parameters. Group M1 showed greater involvement of the right ventricle (RV), expressed as wider low-voltage area, compared to group M0, both at bipolar and unipolar mapping (Table 1). At 37±24 months of FU, there were 12 VA in group M1 vs 1 VA in group M0 (24% vs 10%, p=0.44). VA predictors among Group M1 were the presence of left ventricular systolic dysfunction (HR 3.5, 95% CI 1.3-9.4, p=0.01) and ventricular tachycardia (VT) induction at EPS (HR 5.3, 95% CI 1.9-14.9, p=0.001). At multivariate analysis, inducible VT remained the only independent predictor of VA in pts with myocarditis (HR 4.1, 95% CI 1.3-12.6, p=0.015).
Conclusions: A higher degree of RV unipolar and bipolar mapping alterations was observed in pts with biopsy-proven myocarditis, confirming that substrate alteration at EAM reflects histological abnormalities in these pts. VT inducibility was the only independent predictor for VA in pts with biopsy-proven myocarditis.