Efficacy of steroid therapy for pacing failure in a patient with chronic myocarditis.

A 66-year-old man had a progressive increase in the pacing threshold over a one-year period, resulting from chronic myocarditis. Following steroid therapy, the pacing threshold decreased and became stabilized, and was accompanied by a decrease in the serum creatine kinase, cardiac myosin light chains and pro-collagen III peptide values, but cardiac function did not improve. Endocardial biopsy showed that there was no progression in the fibrosis. The pacing failure improved, but the cardiac function did not. It was believed that the steroid therapy suppressed the progression of the inflammation and fibrosis caused by the chronic myocarditis.