Abstract Body (Do not enter title and authors here): Introduction: Cardiac ¹⁸FDG-PET is frequently utilized to noninvasively diagnose inflammatory cardiomyopathies such as cardiac sarcoidosis (CS). Many patients are diagnosed with presumptive isolated CS based on cardiac ¹⁸FDG-avidity and the Japanese Circulation Society (JCS) guidelines. However, individuals with genetic cardiomyopathies present similarly to CS, are often ¹⁸FDG-avid, and may be misdiagnosed with isolated CS.
Aims: Determine the prevalence of pathogenic or likely pathogenic variants (P/LP) in patients with ¹⁸FDG-avid cardiomyopathy and evaluate how ¹⁸FDG avidity may impact prognosis.
Methods: This is a single center, retrospective analysis of patients who had undergone both cardiac ¹⁸FDG-PET and commercial genetic testing with a comprehensive cardiomyopathy panel (Invitae). Patients with biopsy-proven extracardiac or CS were excluded. Group comparisons made using Chi-square. The composite endpoint of cardiac mortality, sustained VT, LVAD, heart transplant, and heart failure hospitalization was compared between groups using Cox Proportional Hazard’s Model.
Results: Of 128 patients with both cardiac ¹⁸FDG-PET and genetic testing, 112 patients (30% women; mean age 56) met our inclusion criteria. ¹⁸FDG-avidity was present in 54 (48%), of which 9 (17%) had P/LP ([list genes here]). Of these 9, 5 (56%) met JCS diagnostic criteria for isolated CS, 4 were clinically diagnosed with CS, and 2 had been immunosuppressed prior to their genetic testing results. Baseline characteristics were similar between ¹⁸FDG-avid and ¹⁸FDG-negative patients with genetic cardiomyopathies (Figure 1). P/LP prevalence was significantly higher in the ¹⁸FDG-negative group (13, 22%, p=0.01). LP/P variants were most commonly found in LMNA (n=10). Among patients with genetic cardiomyopathy, there was no significant difference in the composite endpoint between ¹⁸FDG-avid and FDG-negative groups (Figure 1; HR 2.3 (95% CI: 0.7-7.2, p-value 0.17).
Conclusions: Genetic cardiomyopathies are often mis-diagnosed as isolated CS based on ¹⁸FDG-avidity, and genetic testing should be performed prior to diagnosing isolated CS. Larger, multi-center studies are needed to determine if ¹⁸FDG-avidity predicts prognosis in genetic cardiomyopathies.