Hypersensitivity myocarditis: Findings in native and transplanted hearts.

Seven explanted hearts from a total of 288 heart transplants performed at UCLA Medical Center had histologic evidence of hypersensitivity myocarditis (prevalence = 2.4%). Three patients had a clinical history of drug allergy, and two had a clinically documented drug reaction prior to transplant. Three patients had peripheral eosinophilia prior to transplant. Five patients with hypersensitivity myocarditis had dilated cardiomyopathy, one had congenital abnormalities, and one had ischemic heart disease. In the period up to 3 weeks posttransplant, four patients had episodes of acute rejection (ISHLT grade 2 to 4) with eosinophils histologically. Results suggest that hypersensitivity myocarditis may have an increasing prevalence in the native heart before transplant and in the newly transplanted heart.