Circadian variation in ischemic threshold in patients with stable angina: relation to plasma endothelin-1.
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.
Li
Jian-Jun
JJ
Department of Cardiology, People's Hospital of Medical School, Wuhan University, PR China. lijnjn@263.net
Huang
Cong-Xin
CX
Fang
Chun-Hong
CH
Chen
Fang
F
Jiang
Hong
H
Tang
Qi-Zhu
QZ
Li
Geng-Shan
GS
D000328:Adult; D000787:Angina Pectoris / Q000097:blood*; D002940:Circadian Rhythm; D019332:Endothelin-1 / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000097:blood*
D019332:Endothelin-1