Assessment of acute myocarditis by cardiovascular MR: diagnostic performance of shortened protocols

The recommended cardiovascular magnetic resonance (CMR) diagnostic criteria for active myocarditis ("Lake Louise Criteria") are based on edema-sensitive (T2-weighted) imaging and two different contrast-enhanced techniques, the early gadolinium enhancement ratio (EGEr) and late gadolinium enhancement (LGE). Because fast spin echo sequences used for determining the EGEr and edema-sensitive T2-weighted sequences have inconsistent image quality, these components are often skipped in institutional standard protocols. We aimed to compare the diagnostic performance of the Lake Louise Criteria with and without T2-weighted or early gadolinium-enhanced CMR imaging in a clinical setting. We investigated 35 patients with suspected acute myocarditis (27 males; Age 39.8 ± 16.6) and 10 healthy controls (5 males; age 33.8 ± 10.4). CMR sequences investigated included an edema-sensitive short-T1 triple inversion recovery, T1-weighted turbo spin echo imaging before and within 4 min after gadolinium injection (EGEr), and a phase sensitive inversion-recovery gradient echo sequence 5-10 min after gadolinium injection (LGE). Quantitative and qualitative image analyses, respectively, were performed for EGEr and areas with increased signal in LGE and edema-sensitive images. EGEr, T2, and LGE burden were significantly higher in patients than in controls (EGEr: 5.8 ± 3.0 vs. 2.5 ± 1.7; p = 0.002, T2: 24 vs. 0; p < 0.001, LGE: 27 vs. 4; p < 0.05). The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were as follows: EGEr: 66, 90, 96, 43, and 72%; T2: 69, 100, 100, 53, and 76%; LGE: 77, 60, 87, 43 and 73%; T2 and/or LGE: 91, 60, 89, 67, 84% Lake Louise Criteria, "two out of three": 80, 90, 96, 53, and 82%. The sensitivity of "T2 and/or LGE" was significantly higher than the Lake Louise Criteria (p < 0.05), while the overall diagnostic accuracy was not statistically different. The overall diagnostic accuracy "T2 and/or LGE" was significantly better than that of LGE alone. The positive likelihood ratio was higher for the Lake Louise Criteria (7.7) than for EGE alone (6.3), T2 and/or LGE (2.3) or LGE alone (1.9). In patients with clinical evidence for relevant active myocarditis, skipping T2-weighted imaging or early GD enhancement is associated with a significantly lower positive likelihood ratio, while the removal of Early Gd Enhancement imaging does not change diagnostic overall accuracy, while reducing sensitivity. Thus, in patients where a high positive likelihood ratio is needed, the full Lake Louise Criteria including Early Gd enhancement and edema-sensitive T2-weighted imaging should be used until alternative approaches are developed.