BACKGROUND: Myocarditis can occasionally lead to sudden death and may progress 
to dilated cardiomyopathy in up to 10% of patients. Because the initial onset is 
difficult to recognize clinically and the diagnostic tools available are 
unsatisfactory, new strategies to diagnose myocarditis are needed.
METHODS AND RESULTS: Cardiovascular MR imaging (CMR) was performed in 32 
patients who were diagnosed with myocarditis by clinical criteria. To determine 
whether CMR visualizes areas of active myocarditis, endomyocardial biopsy was 
taken from the region of contrast enhancement and submitted to histopathologic 
analysis. Follow-up was performed 3 month later. Contrast enhancement was 
present in 28 patients (88%) and was usually seen with one or several foci in 
the myocardium. Foci were most frequently located in the lateral free wall. In 
the 21 patients in whom biopsy was obtained from the region of contrast 
enhancement, histopathologic analysis revealed active myocarditis in 19 patients 
(parvovirus B19, n=12; human herpes virus type 6 [HHV 6], n=5). Conversely, in 
the remaining 11 patients, in whom biopsy could not be taken from the region of 
contrast enhancement, active myocarditis was found in one case only (HHV6). At 
follow-up, the area of contrast enhancement decreased from 9+/-11% to 3+/-4% of 
left ventricular mass as the left ventricular ejection fraction improved from 
47+/-19% to 60+/-10%.
CONCLUSIONS: Contrast enhancement is a frequent finding in the clinical setting 
of suspected myocarditis and is associated with active inflammation defined by 
histopathology. Myocarditis occurs predominantly in the lateral free wall. 
Contrast CMR is a valuable tool for the evaluation and monitoring of 
inflammatory heart disease.