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Meta-Analysis of CMR in Acute Myocarditis
Study Questions:
What is the diagnostic accuracy of various cardiovascular magnetic resonance (CMR) index tests for the diagnosis of acute myocarditis in adult patients?
Methods:
The investigators searched MEDLINE, EMBASE, Cochrane Library, SCOPUS, and Web of Science up to April 21, 2017, and considered all diagnostic cohort and case-control studies that used either endomyocardial biopsy or clinical criteria for the diagnosis of acute myocarditis. They used the Quality Assessment of Diagnostic Accuracy Studies-2 tool to assess the quality of included studies. The authors performed meta-analyses using hierarchical models to produce summary receiver operator characteristic ROC (HSROC) curves and 95% prediction regions for statistical analysis.
Results:
Twenty-two studies were included in the systematic review. Because significant heterogeneity existed among the studies, the investigators only presented hierarchical ROC curves. The areas under the curve (AUC) for each index test were for T1 mapping 0.95 (95% confidence interval [CI], 0.93-0.97), for T2 mapping 0.88 (95% CI, 0.85-0.91), for extracellular volume fraction (ECV) 0.81 (95% CI, 0.78-0.85), for increased T2 ratio/signal 0.80 (95% CI, 0.76-0.83), for late gadolinium enhancement (LGE) 0.87 (95% CI, 0.84-0.90), for early gadolinium enhancement (EGE) 0.78 (95% CI, 0.74-0.81), and for the Lake Louise criteria 0.81 (95% CI, 0.77-0.84). Native T1 mapping had superior diagnostic accuracy across all index tests. The AUC of T2 mapping was greater than the AUC of increased T2 ratio/signal and EGE, whereas ECV showed no superiority compared with other index tests. LGE had better diagnostic accuracy compared with the classic CMR index tests, similar accuracy with T2 mapping and ECV, and only T1 mapping surpassed it.
Conclusions:
The authors concluded that novel CMR mapping techniques provide high diagnostic accuracies for the diagnosis of acute myocarditis.
Perspective:
This meta-analysis reports that the accuracy of standard CMR techniques for the diagnosis of acute myocarditis is good, but can be further improved with the addition of novel parametric mapping techniques (T1 and T2 mapping). Furthermore, in an acute clinical setting, imaging of myocardial edema by T2-weighed sequences could be replaced by native T2 mapping, and similarly, imaging of myocardial hyperemia using T1-weighted sequences could be replaced by native T1 mapping. Of note, LGE has high diagnostic accuracy and can constitute the third component of the revised CMR criteria for acute myocarditis. It appears that novel CMR mapping techniques provide high diagnostic accuracies for the diagnosis of acute myocarditis and add incremental value to the elements of the standard Lake Louise criteria for diagnosis.
Keywords: Diagnostic Imaging, Edema, Gadolinium, Heart Failure, Hyperemia, Magnetic Resonance Imaging, Myocarditis, Myocardium
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