Immunosuppressive therapy in myocarditis

Although there is general agreement on the favorable effect of immunosuppression in eosinophilic, granulomatous, giant-cell myocarditis and in lymphocytic myocarditis associated with connective tissue disorders and with rejection of a transplanted heart, its therapeutic role in lymphocytic inflammatory cardiomyopathy (ICM) is still debated. Previous retrospective studies reported a relevant clinical benefit in 90% of patients with virus-negative ICM and no response or cardiac impairment in 85% of those with virus-positive ICM following immunosuppression. Other studies identified cardiomyocyte HLA upregulation as an additional indicator of ICM susceptibility to immunosuppressive therapy. Recently in a single-center randomized prospective double-blind trial using a combination of prednisone and azathioprine in addition to supportive treatment in 85 virus-negative ICM patients, a significant improvement in left ventricular (LV) ejection fraction and a significant reduction in LV dimensions in 88% of 43 treated patients compared with 42 patients receiving placebo who showed a cardiac impairment in 83% of cases (TIMIC study) was reported. These data confirm the efficacy of immunosuppression in virus-negative ICM. Lack of response in 12% of cases suggests the presence of unscreened viruses or mechanisms of damage and inflammation not susceptible to immunosuppression. Recovery of cardiac function in responders to immunosuppression was associated with inhibition of cardiomyocyte death, increased cell proliferation and with newly synthesized contractile material.