Rate and patient features associated with recurrence of acute myocarditis

•Recurrence of acute myocarditis is studied in multihospital registry setting.•Overall recurrence rate during 4.5 year follow-up is found to be 10.3%.•Prolonged initial admission, ventricular arrhythmias and younger age predicted recurrence.

BackgroundRate and patient features associated with recurrence after acute myocarditis are largely unknown.Methods and resultsFirst recurrence of acute myocarditis was studied in 1662 patients aged 16–70 years using a registry data of 29 hospitals in Finland (median follow-up 4.5 years). Matched intoxication patients served as controls. Incidence rate of first time hospitalization due to acute myocarditis was 5.52 (CI 5.26–5.79) per 100,000 person-years during 2001–2008. During the first 30 days 5.5% (CI 3.5–4.4%) of patients were re-admitted to hospital with acute myocarditis (p < 0.0001 vs. controls). After 30 days, recurrence rate was 7.0% (CI 5.7–8.6%; p < 0.0001 vs. controls). Acute myocarditis recurred after 365 days in 4.7% (CI 3.2–6.7%) of patients (p < 0.0001 vs. controls). During the whole follow-up, recurrence rate was 10.3% (CI 8.8–12.1%; p < 0.0001 vs. controls) with median recurrence time of 34.5 days. Prolonged (> 7 days) initial admission was associated with recurrences during (HR 2.9; CI 1.6–5.2) and after first month (HR 1.8; CI 1.2–3.2), and overall (HR 2.0; CI 1.3–3.2). Ventricular arrhythmia at initial occurrence was associated with recurrence after 30 days (HR 8.6; CI 2.5–30.1), after 1 year (HR 22.6; CI 2.5–201.4) and overall (HR 6.7; CI 2.3–6.7). Other features associated with recurrence were younger age (> 365 days), inflammatory bowel disease (during first month), and chronic pulmonary disease (≥ 30 days).ConclusionsAcute myocarditis reoccurs in a significant proportion of patients. Prolonged initial admission, ventricular arrhythmias, younger age, inflammatory bowel disease and chronic pulmonary disease are associated with recurrences at different phases after acute myocarditis.