Comparative Diagnostic Performance of Cardiac MRI and FDG-PET in Myocardial Inflammation: A Systematic Review and Meta-Analysis.

Cardiac inflammation, including myocarditis and cardiac sarcoidosis, poses significant risks and is a diagnostic challenge that is associated with heart failure, arrhythmias, and sudden cardiac death. Endomyocardial biopsy remains the reference standard but is limited by invasiveness, sampling error in patchy disease, and procedural risk. Noninvasive imaging, particularly cardiac magnetic resonance (CMR) and fluorodeoxyglucose F-18 positron emission tomography (18F-FDG-PET), is therefore central to diagnosis and follow-up. This systematic review and meta-analysis compared the diagnostic performance of CMR and FDG-PET, focusing on sensitivity, specificity, and clinical utility. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020, we searched PubMed, MEDLINE, Embase, Scopus, and the Cochrane Library through October 2025. We included prospective and retrospective adult studies of suspected or confirmed cardiac inflammation undergoing CMR or FDG-PET. Two reviewers independently extracted data and assessed quality with QUADAS-2. Pooled sensitivity and specificity were estimated using a random-effects model, heterogeneity was assessed with the I² statistic, and hierarchical summary receiver-operating characteristic (HSROC) curves were used to examine threshold effects. Twenty-six studies met the inclusion criteria (17 CMR, 9 FDG-PET). CMR showed consistent accuracy with a pooled sensitivity of 0.89 (95% CI 0.85-0.92) and a specificity of 0.87 (95% CI 0.83-0.90). FDG-PET had higher sensitivity, 0.93 (95% CI 0.89-0.96), but lower and more variable specificity, 0.71 (95% CI 0.62-0.79). Both modalities are valuable and complementary. CMR's high, reliable specificity and tissue characterization (edema, fibrosis) make it an appropriate first-line test without ionizing radiation. FDG-PET's greater sensitivity suits the detection of active metabolic inflammation, particularly in sarcoidosis, when strict patient preparation limits false positives. These results support a stepwise approach: CMR first, with FDG-PET for equivocal cases or when assessment of active disease is needed.