Related Experiment Videos
Circadian variation in ischemic threshold in patients with stable angina: relation to plasma endothelin-1
Jian-Jun Li1, Cong-Xin Huang, Chun-Hong Fang
1Department of Cardiology, People's Hospital of Medical School, Wuhan University, PR China. lijnjn@263.net
Insights
Chronic coronary heart disease patients experience a lower ischemic threshold in the morning, linked to higher plasma endothelin-1 (ET-1) levels. This circadian variation suggests ET-1 influences morning cardiac events.
Area of Science:
- Cardiology
- Circadian Biology
- Vascular Physiology
Background:
- Coronary heart disease (CHD) patients exhibit diurnal variations in cardiovascular events.
- Endothelin-1 (ET-1) is a potent vasoconstrictor implicated in cardiovascular pathology.
Purpose of the Study:
- To investigate the circadian variation in ischemic threshold in stable angina patients.
- To determine the relationship between plasma ET-1 levels and the ischemic threshold.
Main Methods:
- 21 stable angina patients underwent treadmill exercise tests twice daily (morning and afternoon).
- Ischemic threshold was defined as heart rate at 1 mm ST depression.
- Plasma ET-1 levels were measured before each exercise test.
Main Results:
- Ischemic threshold was significantly lower in the morning (115 bpm) compared to the afternoon (128 bpm) (p<0.04).
- Plasma ET-1 levels were significantly higher in the morning (6.20 ng/L) versus the afternoon (4.02 ng/L) (p<0.01).
Conclusions:
- Circadian variation in plasma ET-1 levels is a likely mechanism contributing to reduced ischemic threshold in the morning.
- These findings highlight the importance of diurnal patterns in managing coronary heart disease.
Abstract:
To investigate circadian variation in ischemic threshold in chronic coronary heart disease (CHD) and its relation to plasma endothelin-1 (ET-1), 21 patients with stable angina underwent treadmill exercise tests twice within a day, performed at 8-9 AM for the first test and at 3-4 PM for the second one. Ischemic threshold was defined as the heart rate at the onset of 1 mm ST segment depression during exercise tests. Blood samples were taken at 5 minutes before each exercise test, and plasma ET-1 was measured for determining the possible relation to ischemic threshold in patients with CHD. The results showed that the heart rate-ischemic threshold in individual patients varied by 10 +/- 1% (range, 2-15%) in the morning and 9 +/- 1% (range, 2-14%) in the afternoon, while there was a mean (11.2%) reduction in the ischemic threshold between 2 time points, with the ischemic threshold being significantly lower in the morning compared with that in the afternoon (115 +/- 22 bpm vs 128 +/- 31 bpm p<0.04). ET-1 values were 6.20 +/- 2.44 ng/L in the morning hours and 4.02 +/- 1.61 ng/L in the afternoon hours, with a statistical significant difference (p<0.01). In conclusion, the present study indicated that circadian variation of plasma levels of ET-1 was likely to be one of the most likely mechanisms involved in reduction in the ischemic threshold in the morning hours.