Abstract 4369352: Lipoprotein (a) [Lp(a)] levels are not associated with MACE outcomes in patients with suspected CAD referred for Cardiac PET/CT stress tests in an integrated health system

Background: Lipoprotein (a), or Lp(a), is a type of ApoB 100 cholesterol that is associated with coronary artery disease. However, the prevalence of ordering this test is low (<1% of patients) in the USA, despite the relatively low costs of the test. We examine the utility of Lp(a) in predicting PET/CT stress outcomes or augmenting findings for the prediction of major adverse cardiovascular events (MACE). Methods: This is an observational study of all adult patients undergoing a PET/CT stress test in Intermountain Health from 2013-2023 with a coronary artery calcium (CAC) score, PET/CT conclusion, and a Lp(a) test value (n=1001). We evaluated whether Lp(a) values were associated with positive PET/CT (ischemic burden >10% or ischemic burden between 5 and 10% with a high-risk categorization by a cardiologist, and CAC percentages based on age and sex. We examined the association of Lp(a) with one-year MACE (including all-cause death, revascularization, and/or myocardial infarction), while adjusting for CAC percentages and PET/CT reading. Additionally, we evaluated these same outcomes for high Lp(a) (>50) vs low Lp(a) (<26) for young males (<55 years) and females (<65 years). Results: XX patients qualified for the study. The average age was 64±10.7 years and 44% were female. The median Lp(a) was 15 mg/dL (IQR: 6,61), with maximum of 374 mg/dL. Most (84%) had some CAC present, and 26% had CAC values above the 90th percentile for their age and sex. The PET/CT was positive in 9%. Lp(a) was not associated with CAC percentiles (p=0.14) or positive PET stress test result (p=0.38). There were a total of 54 (5%) 1-year MACE outcomes. While both CAC percentile and a positive PET/CT test result were associated with MACE, Lp(a) was not (p=0.31). There were a total of 305 younger males/females, and restricting to this group did not show significant associations. Conclusion: In this highly selected cohort with CAC and Lp(a) evaluation referred for PET/CT, there were few MACE events or positive PET/CTs. Lp(a) was not associated with PET/CT and MACE outcomes, although the power of the study was limited. We recommend increased clinical Lp(a) testing and further study.