Background: Atrial fibrillation (AF) is the most common cardiac arrhythmia, but the prevalence of silent AF is not known, especially in older women. Although AF is less common in women, it confers a greater risk for stroke. Whether AF risk scores might be utilized to identify a population of women at higher risk for silent AF is unknown.
Objective: To determine the prevalence of silent AF in a multiethnic population of older women at higher predicted AF risk on serial ECG patch monitoring.
Methods: We prospectively enrolled subjects with no clinical history of AF but a 5-year predicted risk of new-onset AF ≥5% by CHARGE-AF score from the Women’s Health Initiative Strong and Healthy (WHISH) trial of 49,333 postmenopausal women. Participants were randomly selected to undergo prospective screening with 7-day cardiac patch monitors (Cardiac Insight, Bellevue, WA) at 0, 6, and 12 months as part of WHISH STAR, a sub-study to determine whether WHISH physical activity (PA) intervention affects incident AF. Presence of AF was defined as 30 seconds of AF. This analysis examines all baseline and 79% of the 6-month patches with full 6 and 12-month follow-up to be included in the final presentation.
Results: 1051 women completed baseline and 830 completed 6-month cardiac patch monitors thus far. 91% of participants were White, 5.2% Black, 1.7% Asian, 1.4% Hispanic, and 0.4% American Indian or Alaskan Native. The average age at enrollment was 81 years. At baseline, 26 individuals were found to have AF (2.6%). Among women free of AF at baseline, an additional 11 (1.1% of the population) were found to have AF at 6 months for a combined total of 37 (3.6% of the population). Seven individuals (0.7%) had persistent AF. Among those with paroxysmal AF, the median overall AF burden was 6.9%; the median duration of longest episode of AF was 253 minutes. There was a wide range of longest episodes in the overall cohort: 3 were <60 minutes, 24 were 1 and 24 hours, and 10 were >24 hours. Median heart rates in AF ranged from 60-128 bpm with a median average of 87 bpm.
Conclusion: Silent AF of a considerable burden is a common finding in prospectively screened, high-risk post-menopausal women with an increase in AF detection from 2.6% to 3.6% after repeat ECG patch monitoring at 6 months.