Methods. We randomly assigned 111 patients with a histopathological diagnosis of myocarditis and a left ventricular ejection fraction of less than 0.45 to receive conventional therapy alone or combined with a 24-week regimen of immunosuppressive therapy, Immunosuppressive therapy consisted of prednisone with either cyclosporine or azathioprine, The primary outcome measure was a change in the left ventricular ejection fraction at 28 weeks.

Results. In the group as a whole, the mean (+/-SE) left ventricular ejection fraction improved from 0.25+/-0.01 at base line to 0.34+/-0.02 at 28 weeks (P<0.001), The mean change in the left ventricular ejection fraction at 28 weeks did not differ significantly between the group of patients who received immunosuppressive therapy (a gain of 0.10; 95 percent confidence interval, 0.07 to 0.12) and the control group (a gain of 0.07; 95 percent confidence interval, 0.03 to 0.12), A higher left ventricular ejection fraction at base line, less intensive conventional drug therapy at base line, and a shorter duration df disease, but not the treatment assignment, were positive independent predictors of the left ventricular ejection fraction at week 28, There was no significant difference in survival between the two groups (P=0.96), The mortality rate for the entire group was 20 percent at 1 year and 56 percent at 4.3 years, features suggesting an effective inflammatory response were associated with less severe initial disease.

Conclusions. Our results do not support routine treatment of myocarditis with immunosuppressive drugs. Ventricular function improved regardless of whether patients received immunosuppressive therapy, but long-term mortality was high.