Usefulness of Pericardial Effusion as New Diagnostic Criterion for Noninvasive Detection of Myocarditis

Cardiovascular magnetic resonance (CMR) imaging holds promise for diagnosing myocarditis in vivo. The CMR diagnosis of myocarditis is determined by the ventricular morphology/function, late gadolinium enhancement, and T2-weighted imaging for myocardial edema. However, in routine clinical practice, we encounter patients with suspected myocarditis in the absence of left ventricular dysfunction, myocardial edema, or late gadolinium enhancement. In the present study, we sought to determine whether the presence of pericardial effusion could serve as a new diagnostic criterion and improve the sensitivity of CMR imaging to detect myocarditis. A total of 35 consecutive patients with biopsy proven virus-associated myocarditis, onset of clinical symptoms within the past 3 months, and normal left ventricular function were enrolled in the present study. All patients underwent echocardiography, CMR imaging, and endomyocardial biopsy for workup of myocarditis. Late gadolinium enhancement was present in 16 patients (46%). Myocardial edema on T2-weighted imaging was present in 4 patients, but in just 1, it was the only abnormal finding. Pericardial effusion was present in 14 patients (40%). In 7 patients with myocarditis (20%), pericardial effusion was the only abnormal finding. Pericardial effusion, used as an additional diagnostic criterion, improved the sensitivity of CMR imaging for myocarditis from 46% to 66% (p = 0.023). In conclusion, pericardial effusion detected by CMR imaging might serve as a new diagnostic criterion for the noninvasive diagnosis of myocarditis in patients with recent onset of clinical symptoms and normal left ventricular function.