Date of Award

Summer 8-25-2023

Document Type

Thesis

Degree Name

Master of Medical Science (MMSc)

First Advisor

John A. Elefteriades, MD PhD (hon)

Abstract

Abstract:

Lipid Profiles in Patients with Descending Aortic Aneurysms

Objective

We previously reported that, paradoxically, patients with ascending thoracic aortic aneurysms (ATAAs) are largely spared from atherosclerosis. They have lower coronary and total body calcium scores, lower intimal medial thickness (IMT), and almost complete protection from myocardial infarction. Additionally, ATAA patients have low low-density lipoprotein (LDL) levels. We have not explored these relationships in descending aortic aneurysm (DescAA) patients. In this report, we aim to explore lipid profiles and their association with DescAA.

Methods

We identified 298 patients with DescAA (≥ 4 cm) imaged between 2013 and 2020. This case-control study collected information on lipid profiles (LDLs, HDLs, Total Cholesterol, Triglycerides) and C-reactive protein (CRP). We compared lipid profiles with a non-aneurysm population (National Health and Nutrition Examination Survey) propensity matched for age, gender, hypertension, BMI, smoking status, statin use, and diabetes. We calculated the odds of aneurysm at different lipid values. Patients with concurrent ATAA and/or Marfan’s syndrome were excluded. The absolute standardized mean difference between all covariates for the two groups was ≤12%, indicating adequate matching.

Results

A restricted cubic spline model revealed an inverse relationship between LDL, HDL, and Total Cholesterol levels and odds of DescAA. Lower LDL (OR 1.56; 95% CI 1.03–2.35), HDL (OR 2.86; 95% CI 1.78-4.59), and total cholesterol levels (OR 6.81; 95% CI 3.35-13.82) were associated with higher odds of DescAA compared with NHANES controls. A positive relationship was demonstrated in CRP and Cholesterol:HDL ratio, finding increased odds of DescAA with higher CRP (OR 56.63; 95% CI 21.03-152.54) and Cholesterol:HDL ratio (OR 2.00; 95% CI 1.15-3.45). A sigmoidal relationship between Triglyceride levels and odds of DescAA was observed.

Conclusions

LDL and total cholesterol are known to contribute to the development of atherosclerosis, however our results show that elevated serum LDL and total cholesterol decrease the odds of DescAAs. This is a powerful but counterintuitive finding. This novel data on lipid profile levels provides a new piece of the puzzle in understanding the relationship between DescAA and atherosclerosis. Mechanisms of this relationship remain to be investigated.

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