Should we fear infarct-like myocarditis?

Abstract Introduction Infarct-like myocarditis is the common presentation of acute myocarditis with a good prognosis, mentioned in the literature. The restriction of physical activity for up to 6 months is usually recommended. The aim of our study was to show the characteristic features and specificity of this particular presentation of myocarditis and to evaluate its prognosis, relative to physical activity, after hospital discharge. Methods From 2012 to 2016, 93 patients were hospitalized with acute myocarditis at the University Hospital of Pilsen, 73 (78%) of them had infarct-like myocarditis and were evaluated by basic diagnostic parameters. Thirty-two patients with infarct-like myocarditis were involved in our prospective observational study where echocardiography (ECHO), magnetic resonance imaging (MRI) including late gadolinium enhancement (LGE) volume, bicycle ergometry (BE) as well as troponin screening tests were regularly performed. None of the patients were professional athletes. One month after hospital discharge, all patients underwent bicycle ergometry without any load limitation. After the 1-month follow-up, patients were allowed to increase physical exertion gradually to included job performance. Results Initially, mild left ventricular systolic dysfunction was found in 43.8%, that was normalized before the first outpatient follow-up. Other patients had normal systolic function. Initially, all of the patients had significantly elevated troponin level. After 1 and 6 months, hypersensitive troponin values were under the 99th percentile of the healthy population. All of the patients had positive LGE in subepicardial localization. After 1 month, the LGE volume median had decreased by up to 53% and after 6 months it had decreased by up to 40% of the original value. The achieved exertion during BE, at the 6-month follow-up (9.7 ± 2.2 METs) was statistically significantly better than after the 1-month follow-up (8.9 ± 2.1 METs, p  = 0.0023). On the last BE follow-ups (9.3 ± 2.1 METs), no significant change was seen ( p  = 0.2331). The average follow-up time was 2 years. Conclusion Infarct-like myocarditis was the most common presentation of acute myocarditis during the observation time. No patient had an early recurrence of the disease (i.e., within 1 year) and no left ventricular (LV) systolic dysfunction was developed. Infarct-like myocarditis has a specific feature that differs from other types of myocarditis. It has good prognosis, which is independent of physical exertion starting 1 month after hospital discharge.