Prognostic Impact of Extent, Severity, and Heterogeneity of Abnormalities on 18F-FDG PET Scans for Suspected Cardiac Sarcoidosis

Abstract

Objectives: This study sought to evaluate the incremental value of quantifying the extent and severity of myocardial perfusion and ¹⁸F-labeled fluorodeoxyglucose (FDG) abnormalities in predicting adverse outcomes among patients with suspicion for cardiac sarcoidosis (CS).

Background: Positron emission tomography (PET) with FDG is a key component of the noninvasive assessment of patients with suspected CS. However, the optimal method for image interpretation has not been defined.

Methods: A retrospective analysis was performed of 203 patients who underwent perfusion and FDG-PET imaging to evaluate for CS. Imaging findings were scored by conventional 3-category methods (normal perfusion and metabolism, abnormal perfusion or metabolism, abnormal perfusion and metabolism) and by summed scores using the 17-segment model to represent extent and severity of disease. Heterogeneity of metabolism was quantified using the coefficient of variation (SD divided by the mean) of FDG uptake. Multivariable Cox models were developed to assess associations between imaging findings and adverse events (death, heart transplant, or ventricular arrhythmia requiring defibrillation).

Results: The indication for FDG-PET was ventricular arrhythmia in 69 (34%), heart block in 16 (8%), cardiomyopathy in 54 (27%), and other indications in 64 (32%). There were 63 patients who developed adverse events over a mean follow-up of 1.8 years. After robust adjustment, only the summed score in segments with a perfusion-metabolism mismatch and the coefficient of variation were important prognostically (p = 0.029 and p = 0.041, respectively).

Conclusions: Quantitative measures of extent and severity of perfusion-metabolism mismatch and coefficient of variation of FDG uptake provide an incremental prognostic advantage in patients undergoing FDG-PET for CS. These results support the use of a more detailed analysis of imaging findings, as is conventional in coronary artery disease.

Keywords: cardiomyopathy; inflammation; scar; ventricular tachycardia.