Abstract Body (Do not enter title and authors here): Introduction
Ischemic dilated cardiomyopathy (IDCM) is defined as DCM caused by severe stenosis of one or more coronary arteries. Patients with non-ischemic dilated cardiomyopathy (NIDCM) have normal coronary arteries and may possess rare disease-causing variants in cardiac proteins such as TTN. However, IDCM and NIDCM share echocardiographic and pathologic features, possibly suggesting a shared etiology.

Hypothesis
There is a similar prevalence of pathogenic (P)/likely pathogenic (LP) variants in patients with IDCM compared to patients with NIDCM.

Aims
We compared the prevalence of P/LP genetic variants in DCM-associated genes in a cohort of patients with NIDCM or IDCM who received a heart transplant.

Methods
We conducted a retrospective cohort study of patients who received a heart transplant between May 2017 and October 2023 at Cedars Sinai Medical Center in Los Angeles, CA. All subjects had LVEF ≤ 50% and LVEDD ≥ 95^th percentile for sex and height. Whole exome sequencing was performed on explanted heart tissue. We assessed for rare variants (minor allele frequency <0.1%) in genes with a definite, strong, or moderate rating in the ClinGen DCM Gene Curation Expert Panel. Variant pathogenicity was interpreted using the American College of Genetics and Genomics criteria for DCM. Ischemic cardiomyopathy was defined by the Felker criteria (Felker et al., JACC 2002).

Results
We included 60 subjects: 16 with IDCM and 44 with NIDCM. There was no difference in LVEF or LVEDD between groups (TABLE). 2/16 (12.5%) patients with IDCM carried a P/LP variant, both of which were in TTN. 11/44 (25.0%) patients with NIDCM carried a P/LP variant: 6 in TTN and 1 each in FLNC, ILK, LMNA, MYH7, and RBM20. The prevalence of TTN variants in each group was similar (12.5% in IDCM vs. 13.6% in NIDCM) and higher than the expected frequency in the general population (0.2%). There was no significant difference in the prevalence of P/LP variants between the groups (chi-squared p-value 0.493, Bayes factor 0.45).

Conclusion
Patients with IDCM exhibited a similar prevalence of P/LP variants to NIDCM patients, which suggests a shared genetic burden. If further studies confirm our findings, genetic testing for individuals with IDCM may be warranted.