The potential additional diagnostic value of assessing for pericardial effusion on cardiac magnetic resonance imaging in patients with suspected myocarditis.

BACKGROUND: The presence of pericardial effusion (PE) is considered to be suggestive of inflammation in suspected myocarditis. However, the incremental value of assessing for PE in addition to comprehensive cardiac magnetic resonance (CMR) imaging remains unclear.

METHODS: In total, 132 patients with suspected acute (AMC) or chronic myocarditis (CMC) were included. All patients underwent endomyocardial biopsy (EMB) and CMR. Imaging protocols included T2 imaging for the assessment of myocardial oedema (oedema ratio [ER]), T1 imaging before and after contrast agent administration for global relative enhancement (gRE) calculation, and late enhancement (LE). Furthermore, the presence and extent of PE were determined. The potential incremental diagnostic value of PE was determined by applying a two, three, or four out of four criteria approach including ER, gRE, LE, and PE.

RESULTS: PE was present in 84 of the 132 patients (63.6%) and was more common in suspected AMC vs. CMC (56 of 70 vs. 28 of 62; P < 0.001). According to EMB results, PE was found in 86% of patients with AMC, 67% with chronic myocarditis, and 56% without evidence of myocardial inflammation. Implementing PE into a three out of four approach did not result in improved accuracy compared with the established two out of three approach using ER, gRE, and LE (59 vs. 68% for the total population, 69 vs. 79% for suspected AMC, and 48 vs. 52% for suspected CMC).

CONCLUSION: The finding of PE in unselected patients with suspected AMC or CMC is not specific to myocarditis. Therefore, with the currently applied criteria and methods, assessment of PE does not improve the diagnostic performance of CMR in this patient cohort.