PET/CT Outperforms CMR in Early Diagnosis of Cardiac Sarcoidosis, Suggests Study

While clinical diagnosis of CS remains exceptionally challenging due to the poor sensitivity of standard endomyocardial biopsies and a noticeable lack of comparative imaging studies defining specific roles during different disease stages, Dr. Muthiah Subramanian and colleagues at the AIG Institute of Cardiac Sciences in Hyderabad, India, aimed to bridge this clinical gap by systematically comparing the diagnostic utility of 18F-FDG PET/CT and CMR in patients presenting with early and late-stage disease.

Therefore, the retrospective study analyzed 102 patients with cardiac sarcoidosis who underwent both PET/CT and MRI scans within two weeks of their initial presentation. Researchers divided these patients into early and late disease stages to evaluate their clinical and radiological responses after four to six months of immunosuppressive therapy.

Key Clinical Findings of the Study Includes:

• Superior Early Detection: The study revealed that 18F-FDG PET/CT detected abnormal myocardial uptake in a full 100% of early CS patients, significantly outperforming CMR, which identified late gadolinium enhancement (LGE) in only 73.2% (p < 0.001).

• Comparable Late-Stage Yield: The study demonstrated that both advanced imaging modalities offered remarkably similar diagnostic accuracy in chronic, late-stage CS, with 18F-FDG PET/CT detecting abnormalities at a rate of 91.3% and CMR at 97.8% (p = 0.498).

• Enhanced Treatment Response: The study highlighted that a complete clinical and radiological response to IST was significantly more frequent among early CS patients compared to the late-stage cohort (62.5% vs. 47.8%, p = 0.019).

• Prognostic Value of Fibrosis Absence: The study found that early CS patients without any LGE achieved a remarkably higher complete response rate to targeted therapy than those already presenting with fibrotic LGE (86.7% vs. 53.7%, p = 0.025).

The results suggest that utilizing early functional metabolic imaging is highly sensitive and prognostically superior to traditional structural imaging for the initial diagnosis of early CS, as evidenced by its flawless 100% detection rate and its unique capability to predict better clinical outcomes before irreversible fibrotic damage manifests.

Thus, the study concludes that clinicians may find practical value in leveraging the functional imaging modality early in the diagnostic pathway to accurately identify active tissue inflammation and to confidently pinpoint potential non-responders who might require prompt advanced heart failure interventions over standard immunosuppression.

Although constrained by its retrospective single-center design, a relatively small sample size, and the absence of advanced parametric mapping techniques, these findings open an encouraging avenue for future comparative investigations incorporating newer radiotracers and refined magnetic resonance protocols to further optimize early detection.

Reference

Subramanian, M., Narasimhan, B., Korabathina, R., Batchu, S., Ravilla, V. V., Roop, M., Yalagudri, S., Saggu, D. K., & Narasimhan, C. (2025). Utility of 18F-FDG PET/CT and Cardiac MRI in early Cardiac Sarcoidosis. Indian Heart Journal, 77, 253–257.