Acute Myocarditis Complicated by Ventricular Arrhythmias: Prevalence, Outcomes and Acute Ablation Results

BackgroundAcute myocarditis is typically self-limiting and resolves spontaneously in most cases. However, ventricular arrhythmias (VA) complications, which may be life-threatening are associated with higher rates of in-hospital complications and mortality. Catheter ablation is occasionally required for acute myocarditis associated ventricular tachycardia (VT), but data on its procedural use and outcomes, in this setting, remain limited. We aimed to determine the prevalence of VA among patients hospitalized for acute myocarditis and to evaluate the subset who underwent in-hospital VT ablation, including their acute outcomes. MethodsRetrospective analyzed data from the National Inpatient Sample (NIS) database for U.S. hospitalizations with a diagnosis of myocarditis between 2016 and 2019. In-hospital outcomes were compared between patients with and without VA. Subgroup analysis examined patients with acute myocarditis associated VT stratified by whether VT ablation was performed. Patient demographics, comorbidities, procedures, and outcomes were identified using ICD-10-CM codes. ResultsAmong an estimated 17,845 hospitalizations for acute myocarditis, 8.4% (n=1,505) had VA (including 7.7% with VT). Patients with VA were more likely to have structural heart disease, renal disease, infectious etiologies, anemia, and atrial arrhythmias, despite lower prevalence of some traditional cardiac risk factors. VA was associated with markedly worse outcomes, including 5.5-fold higher in-hospital mortality (10% vs 1.6%; p<0.001). Multivariate analysis revealed that VA during admission for acute myocarditis was an independent significant risk factor for cardiac complications (aOR=4.8), total complications (aOR=4.2) and in hospital mortality (aOR=5.1) (p<0.001 for each analysis). Among patients with VT, catheter ablation was performed in 13.7% (n=190), more commonly with infectious etiologies. Ablated patients, compared to those without ablation, experienced significantly higher rates of in-hospital complications (73.7% vs 42.3%; p<0.001) and mortality (15.8% vs 6.7%; p<0.001). ConclusionsVA complicating acute myocarditis, portends significantly worse in-hospital outcomes. Although ablation was performed in approximately 1 in 7 patients with VT, those undergoing the procedure had less favorable acute results. Further prospective research is warranted to define optimal criteria for ablation and expected outcomes in this high-risk population.