Abstract 1569: Effects of Postmenopausal Hormone Therapy on Atrial Fibrillation: The Women’s Health Initiative Randomized Controlled Trials
Introduction: Atrial fibrillation is the most prevalent arrhythmia in women and is associated with increased risk of stroke and death. Although rates of atrial fibrillation differ between men and women, the effects of postmenopausal hormone therapy (PHT) on atrial fibrillation have not been well characterized.
Methods: The Women’s Health Initiative randomized controlled trials studied the effects of estrogen (E-alone) and estrogen plus progestin (E+P) compared to placebo on the development of several health outcomes including atrial fibrillation (AF). Incident cases of AF were identified either by discharge codes available from self-reported hospitalizations or with repeat electrocardiograms. The hazards of developing AF were estimated using Cox proportional hazards regression models.
Results: A total of 16,608 participants in the E+P trial were randomized to E+P or placebo and followed for an average of 5.6 years while 10,739 participants in a separate E-alone trial were randomized to E-alone or placebo and followed for an average of 7.0 years. In the E+P trial, the women were on average 63 years of age, 40% were hypertensive, 4% had diabetes and 5% had coronary heart disease. In the E-alone trial, the average age was 63, 45% were hypertensive, 8% had diabetes and 9% had coronary heart disease. There were 389 and 490 incident cases of AF in the E+P and E-alone trials, respectively. There were no statistically significant associations between PHT use and AF in either trial (hazard ratio 0.92, 95% CI 0.75–1.12 in E+P; hazard ratio 1.08, 95% CI 0.90 –1.29 in E-alone). On subgroup analysis of the E-alone trial, however, there was a higher incidence of AF in patients with diabetes (HR 2.15, 95% CI 1.5–3.7) or BMI > 35 (1.56, 95% CI 1.2–2.5) who were randomized to E-alone.
Conclusion: There were no statistically significant differences overall in the risk of developing AF between PHT use and placebo. Certain subgroups at a baseline higher risk for AF may have an augmentation in risk for AF with E-alone use.