A Cross-Sectional Analysis of the Relationship Between Hormone Replacement Therapy and Coronary Artery Calcification

P24 Background: There is evidence that estrogen affects the vascular wall, independent of modifications to plasma lipoproteins, by accelerating reendothelialization of damaged blood vessels and by inhibiting smooth muscle cell proliferation. Therefore, we intended to investigate the relationship between hormone replacement therapy (HRT) use and prevalence of coronary calcium (CC) in postmenopausal women. Methods: Cardiac electron beam computed tomography (EBCT) was performed on 793 postmenopausal women participating in the Cedars-Sinai Cardiovascular Observational Study. At the time of their EBCT, 509 women were receiving HRT and 284 were not receiving HRT. The total coronary calcium score was determined using the Agatston method. A self-report of HRT use was assessed in all participants, as well as measurements of other known cardiovascular risk factors. Results: Independent sample t-tests identified the means of the following variables as significantly different between the two groups of women: age, LDL, HDL, and BMI. Self reports of hypertension, smoking, exercise and diet were similar between the two groups. Analysis of variance, controlling for confounders, showed a significant difference (p<.001) between the marginal means (MM) of the two HRT groups for total coronary calcium score, total number of calcified lesions, and total volume of calcium. The MM total CC score was 96.40 (±256.39) for HRT users and 150.97 (±362.54) for non-users. The MM number of lesions for users was 2.16 (±3.37) and 3.36 (±4.75) for non-users. The MM volume of calcium for users was 0.078 (±0.20) and 0.122 (±0.29) for non-users. Conclusions: Total coronary calcium score, total lesions, and total volume were found to be significantly lower in postmenopausal women receiving HRT than for those not receiving HRT. These findings support the hypothesis that hormone replacement therapy is associated with a lower prevalence of coronary calcium in postmenopausal women, which may be due to the independent effects of estrogen on coronary vessel walls.