Active vs healed myocarditis was found to be associated with more frequent irregular and polymorphic ventricular arrhythmias (VAs), according to study results published in the Journal of the American College of Cardiology.
With no large comparative studies available, the nature of the relationship between different stages of myocardial inflammation and the occurrence of VA has yet to be systematically investigated. Identifying types of VA that are specific to certain stages of myocarditis could help track disease activity.
In this single-center prospective study, 185 patients hospitalized with myocarditis and VA (mean age, 44±15 years; 69% men) were enrolled between January 2013 and September 2017 and followed semi-annually. Types of VA encountered at index hospitalization were ventricular tachycardia (VT), non-sustained VT (NSVT), ventricular fibrillation (VF), and Lown’s grade ≥2 premature ventricular complexes (PVCs). Cardiac magnetic resonance imaging (CMR) and endomyocardial biopsy were used to differentiate active from previous myocarditis. In a subset of 46 participants (24.9%), electroanatomic mapping was performed, followed by VA transcatheter ablation.
The mean left ventricular ejection fraction in this cohort was 49%±14%. At baseline, a greater number of patients with active (n=123; 65%) vs healed (n=62; 33.5%) myocarditis had: VF (8 cases vs 0 case, respectively; P =.053); irregular VA (61% vs 11%, respectively; P <.001) and polymorphic VA, including VT and NSVT (19% vs 2%, respectively; P =.002) and PVCs (63% vs 16%, respectively; P <.001). In patients with healed myocarditis who presented with VT or NSVT, the presence of a right-bundle branch block with superior axis as the dominant morphology predicted an abnormal LV inferoposterior substrate 100%, both when determined using electroanatomic mapping or CMR imaging.
Over a mean follow-up period of 27±7 months, a total of 55 patients (29.7%) had malignant VA, with no significant difference between the active and previous myocarditis groups (P =.385). There was a prevalence of irregular and polymorphic VA in patients with active myocarditis and persistent inflammation during the follow-up (58%), whereas patients with healed myocarditis (43%) had predominantly regular and monomorphic VA (P <.001 for all).
Study limitations include its single-center setup, small sample size, possible overestimation of the arrhythmic burden, unknown disease prevalence, reduced study power, lack of modern T mapping sequences on CMR, and possible modification of VA by ablation in some patients.
“Our findings may help in identifying myocarditis stage in patients with VA, with promising future applications in diagnostic and therapeutic choices,” noted the authors. They recommended that future research examine the role genetics may play in the pathogenesis of myocarditis and VA.
Funding and Conflicts of Interest Disclosures:
Dr Della Bella has served as a consultant for Abbott and Biosense Webster; and has received research grants from Abbott, Biosense Webster, and Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Peretto G, Sala S, Rizzo S, et al. Ventricular arrhythmias in myocarditis. J Am Coll Cardiol. 2020;75(9):1046-1057. doi:10.1016/j.jacc.2020.01.036