Clinical significance of chronic myocarditis: systematic review and meta-analysis.

Chronic myocarditis is a prolonged inflammatory condition in the myocardium and its histological manifestation is defined by the presence of an inflammatory infiltrate. Chronic myocarditis has not been well known and its treatment of chronic myocarditis has not been established. Primary outcome of this study was to assess the efficacy of immunomodulatory treatment in addition to conventional treatment, and secondary outcomes were to clarity the prognosis of natural history of chronic myocarditis and incidence of chronic myocarditis in patients with dilated cardiomyopathy (DCM). We searched for studies in Medline, Embase, Cochrane Central Register of Controlled Trials, and Igaku Chuo Zasshi published between January 1946 and June 2020. Sixteen studies met the inclusion criteria. A meta-analysis revealed that patients receiving immunomodulatory treatment showed an improvement in left ventricular ejection fraction after immunomodulatory treatment compared to the control group (hazard ratio, 16.65; confidence interval, 4.55-28.74; p = 0.007). Five-year survival rate of the patients with inflammatory DCM (iDCM) and DCM was 52.7-70.3% and 51.9-91.1%, respectively. Moreover, 51.5%-62.7% of patients with DCM met the criteria of iDCM. Our systematic review revealed that patients with chronic myocarditis had poor prognosis and immunomodulatory treatment was significantly effective in addition to conventional treatment.