Author + information
- Received September 21, 1995
- Revision received January 5, 1996
- Accepted January 23, 1996
- Published online June 1, 1996.
- David Mulcahy, MD,MRCPI,FESC,
- Nader Dakak, MD,
- Gloria Zalos, RN,
- Neil P. Andrews, MB,MRCP,
- Michael Proschan, PhD,
- Myron A. Waclawiw, PhD,
- William H. Schenke, BA and
- Arshed A. Quyyumi, MD,MRCP,FACC∗
- ↵∗Address for correspondence Dr. Arshed A. Quyyumi, Cardiology Branch, Building, 10 7B15, 10 Center Drive MSC 1650, National Institutes of Health, Bethesda, Maryland 20892.
Objectives. This study sought to compare the circadian variations in transient ischemic activity, mean heart rate and ischemic threshold between women and men with coronary artery disease.
Background. There is a circadian variation in ischemic activity, onset of myocardial infarction and sudden cardiac death in patients with coronary artery disease, but studies assessing ischemia have incorporated predominantly male subjects.
Methods. Thirty-one women and 45 men underwent at least 48 h of ambulatory ST segment monitoring.
Results. There was a similar and significant circadian variation in ischemic activity in both women and men (p < 0.001 and p < 0.0001, respectively), with a trough at night, a surge in the morning and a peak between 1 and 2 pm, corresponding to a similar circadian variation in mean hourly heart rate (p < 0.0001) that was not different between men and women (p = 0.28, power to detect a shift 99.9%). Mean heart rate at onset of ischemia (ischemia threshold) had similar variability in women and men (p = 0.96), and harmonic regression analysis confirmed a significant circadian variation (p < 0.0001), with a trough at night and a peak during activity hours. Heart rate increased significantly in the 5 min before ischemia throughout the 24 h (p < 0.0001), with no gender differences in the pattern of preonset to onset heart rate changes over time (p = 0.52); the smallest differences were recorded in the middle of the night. The majority of ischemic episodes (80%) had a heart rate increase >5 beats/min in the 5 min before ischemia, but there were no gender differences.
Conclusions. Women with coronary artery disease have a pattern of ischemic activity and underlying pathophysiologic mechanisms very similar to men. The importance of increase in myocardial oxygen demand in the genesis of ischemia in both men and women is reflected by similar magnitude of heart rate increases before ischemia. The lower ischemic threshold during the nocturnal hours, when blood pressure is also lower, is consistent with a circadian variation is underlying coronary vascular tone.
- Received September 21, 1995.
- Revision received January 5, 1996.
- Accepted January 23, 1996.