Reduced ¹⁸F-FDG uptake in the basal interventricular septum as a predictor of fatal ventricular arrhythmic events in patients with cardiac sarcoidosis

Background: Patients with cardiac sarcoidosis (CS) are at an increased risk of fatal ventricular arrhythmic events (FVAE). However, the predictive value of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in assessing the risk of FVAE in patients with CS remains uncertain. Methods: We included data from 121 patients with CS (39 men and 82 women; mean age: 59.5 years) who underwent FDG-PET imaging between March 2008 and November 2020, with follow-ups completed in July 2023. Of these, 82 patients had available cardiac magnetic resonance imaging data, including late gadolinium enhancement (LGE). FDG-PET images were analysed using a polar-map model to determine the regional mean percentage uptake relative to the maximal cardiac ¹⁸F-FDG uptake in each of the 17 segments defined by the American Heart Association. Results: Patients experiencing FVAE after FDG-PET (n = 43) showed lower percent uptake in the basal inferoseptal segment compared to those who did not (n = 78) (41.8 ± 15.2 % vs. 54.4 ± 13.8 %, P < 0.001). Patients with a basal inferoseptal percent uptake below the median had a lower FVAE-free survival rate than those with a higher percent uptake (58.1 % vs. 78 % at 5 years, P = 0.007), which was consistent in patients with LGE in the same regions with reduced ¹⁸F-FDG uptake. A Cox hazard model indicated that the FVAE risk decreased with a hazard ratio of 0.862 (95 % CI 0.770–0.964) for every 5 % increase in basal inferoseptal percent uptake (P = 0.009). Conclusion: Reduced ¹⁸F-FDG uptake in the basal interventricular septum, including the inferoseptal segment, may be a valuable predictor of future FVAE in patients with CS.