Heart Rate Response to Exercise Stress Testing in Asymptomatic Women
The St. James Women Take Heart Project
Background— The definition of a normal heart rate (HR) response to exercise stress testing in women is poorly understood, given that most studies describing a normative response were predominately based on male data. Measures of an attenuated HR response (chronotropic incompetence) and age-predicted HR have not been validated in asymptomatic women. We investigated the association between HR response to exercise testing and age with prognosis in 5437 asymptomatic women.
Methods and Results— Participants underwent a symptom-limited maximal stress test in 1992. HR reserve (change in HR from rest to peak), chronotropic index, and age-predicted peak HR were calculated. Deaths were identified to December 31, 2008. Mean age at baseline was 52±11 years, with 549 deaths (10%) over 15.9±2.2 years. Mean peak HR was inversely associated with age; mean peak HR=206–0.88(age). After adjusting for exercise capacity and traditional cardiac risk factors, risk of death was reduced by 3% for every 1–beat-per-minute increase in peak HR, and by 2% for every 1–beat-per-minute increase in HR reserve (P<0.001). Inability to achieve 85% age-predicted HR was not an independent predictor of mortality, but being ≥1 SD below the mean predicted HR or a chronotropic index <0.80 based on the prediction model established by this cohort were independent predictors of mortality (P<0.001 and P=0.023, respectively).
Conclusions— Chronotropic incompetence is associated with an increased risk of death in asymptomatic women; however, the traditional male-based calculation overestimates the maximum HR for age in women. Sex-specific parameters of physiological HR response to exercise should be incorporated into clinical practice.
Received January 19, 2010; accepted May 10, 2010.