Abstract Body (Do not enter title and authors here): Introduction: 18FDG-PET scan has emerged as a modality for identifying inflammatory cardiomyopathies such as cardiac sarcoidosis (CS) by detecting glucose uptake. Guidelines allow for diagnosis of CS based on clinical presentation and 18FDG-avidity without requiring tissue biopsy. However, patients with genetic cardiomyopathies can be 18FDG-avid, potentially leading to misdiagnosis as isolated CS.
Objectives: To evaluate the prevalence of pathogenic and likely pathogenic (P/LP) variants in 18FDG-avid cardiomyopathy and assess the association between FDG-avidity, genetic variants, and heart failure outcomes.
Methods: A multi-center retrospective cohort study combined patients from three centers who underwent both a cardiac 18FDG-PET scan and commercial genetic testing for genetic cardiomyopathies. We excluded patients with biopsy-proven sarcoidosis, as well as those with incomplete 18FDG suppression. Chi-square tests were used to compare between group characteristics, and Kaplan-Meier survival analyses were performed to evaluate time to event outcomes, including a composite of death, LVAD implantation, or heart transplant, based on 18FDG-avidity and genetic status.
Results: Among 459 patients who underwent both a cardiac 18FDG-PET scan and genetic testing, 389 (33% female; mean age 54 years) met the inclusion criteria. 18FDG-avidity was identified in 158 (40%). Within this subgroup, 19 (12%) had a P/LP variant compared with 19% of the 18FDG-negative patients (p=0.051; Figure 1). Baseline characteristics were similar, and a wide array of genes was implicated in 18FDG-avid cardiomyopathy (Figure 2).
Survival analysis revealed no significant difference between the four genotype-FDG subgroups (p=0.13, Figure 3), and 18FDG-avidity was not significantly associated with the composite endpoint in the overall cohort (p=0.35), nor within the subset of patients with P/LP variants (p=0.84), suggesting that 18FDG-avidity did not predict clinical outcomes. The presence of a P/LP variant was associated with an increased incidence of the composite endpoint (p=0.047).
Conclusion: 18FDG-avidity is frequently noted in patients with genetic cardiomyopathy, but was not associated with adverse clinical outcomes, suggesting it may not reflect clinically relevant inflammation. P/LP variants were significantly associated with survival outcomes, highlighting the value of genetic testing in patients with suspected inflammatory cardiomyopathy.