Contrast MR may hold key to diagnosing myocarditis

Contrast-enhanced MR imaging may serve as the key to diagnosing myocarditis, an inflammatory heart condition that leads to chronic dilated cardiomyopathy in as many as one of every 10 patients and sudden death in some cases. A study presented at the SCMR meeting provided a strong argument for adopting the strategy to find and monitor the condition.

"Contrast enhancement is a frequent finding in the clinical setting of myocarditis," said Dr. Heiko Mahrholdt, a cardiologist at Robert Bosch Medical Center in Stuttgart, Germany.

Mahrholdt described his group's experience with 32 patients who presented with symptoms suggesting myocarditis: flulike conditions experienced within two months of hospital admission, chest pain, shortness of breath, tachycardia, and an ECG pattern consistent with the presence of the disease. The study group comprised 26 men and six women. Results were published in the March issue of Circulation.

The ECG-gated, inversion-recovery cardiac MR protocol was performed five to 10 minutes after an infusion of 0.1 mmol/kg of gadolinium. Image acquisition covered the myocardium from apex to base in 6-mm slices. Procedures were completed in 20 to 30 minutes, and two blinded readers interpreted the results.

Contrast enhancement appeared in 28 of the 32 cases, Mahrholdt said. Readers observed patchy enhancement that most often appeared subepicardially in the lateral free wall. Of the 21 cases in which histological material had been harvested from the enhanced regions, 19 confirmed the diagnosis of myocarditis. The enhanced regions were rich in macrophages and lymphocytes indicative of myocardial damage. Contrast-enhanced areas decreased from an average 9% to 3% of left ventricular mass when MR imaging was repeated 12 weeks later. Mahrholdt associated this change with the shrinkage of scar that replaced the necrotic tissue during healing.