Abstract 19087: Endogenous and Exogenous Estrogen Exposure have Synergistic Effects on Mid-life Electrocardiographic PR Interval among Women: the Women’s Health Initiative Hormone Therapy Trial
Introduction: Prior data demonstrates that oophorectomized mice have shorter atrioventricular conduction/ PR and Atrio-His intervals compared to oophorectomized mice receiving exogenous estrogen. We hypothesized that endogenous estrogen exposure from cumulative pregnancies and reproductive period duration would relate to long-term differences in the PR interval and these effects would be modified by exogenous hormone therapy use and hysterectomy status (a proxy for unopposed estrogen usage in humans).
Methods: We studied women free of prevalent cardiovascular disease in the Women’s Health Initiative Hormone Trial. We employed linear regression analysis to relate number of pregnancies and reproductive duration (time from menarche to menopause) with millisecond (ms) changes in PR interval on enrollment electrocardiogram. Multivariable models were adjusted for age, BMI, hypertension, diabetes, income, education, race, region of US, prior breastfeeding, antianxiety medications, antidepressants, lipid medication, and duration. Models were tested for effect modification by categories of prior hormone therapy use and hysterectomy.
Results: Among 40,687 women [mean age 62.36 (SD:6.9) years], number of pregnancies was not related to increased PR interval (p value=0.12). Reproductive period duration was associated with PR interval (p< 0.03) and this effect was modified by current hormone therapy usage and hysterectomy status such that women who never used hormones with an intact uterus had the smallest difference in PR per additional year of reproductive period and current HT users with prior hysterectomy had the greatest difference in PR per additional year of reproductive duration (p interaction <0.0001, see Table).
Conclusions: Our findings suggest that a combination of endogenous and exogenous estrogen exposure have synergistic effects on PR interval in post-menopausal women.
Author Disclosures: N.I. Parikh: None. K. Kapphahn: None. H. Hedlin: None. J.E. Olgin: None. M.A. Allison: None. K.K. Ryckman: None. M.V. Perez: None. M.E. Waring: None. B.V. Howard: None.
This research has received full or partial funding support from the American Heart Association.
- © 2014 by American Heart Association, Inc.