الفهرس 
Introduction & Aim of workOnly 14 pages are availabe for public view
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Abstract
Background: Coronary artery disease (CAD) is a major health problem and a major cause of mortality all over the world. The incidence of acute coronary syndromes had a proved diurnal rhythm being more in the period from 6AM to 12 noon of the day. This could be due to increased platelet aggregability and adhesiveness in this time. The role of the endothelium in this diurnal rhythm and the possibility that it has a diurnal rhythm in its function, has not studied. Aim: To evaluate diurnal changes of endothelium dependent vasodilation in normal subjects and in patients with CAD and to study the effects of some metabolic and haemodynamic parameters on endothelial functions. Methods: 20 patients with CAD and 10 healthy subjects matched in age and sex were subjected to Doppler ultrasound on the right brachial artery at 9AM and 9PM to evaluate endothelial dependent vasodilation in response to reactive hyperaemia. Carotid intimal medial thickness, a amarker of atherosclerosis, was measured in both groups. Also, we studied the effect of some haemodynamic parameters as blood pressure and some inflammatory marker as C.reactive protein on endothelial function. Result: Circadian rhythm of endothelial function in healthy subjects evidenced by morning increase in endothelial dependent vasodilation and loss of this rhythm in CAD patients. Carotid IMT was higher in CAD patients reflecting atherosclerosis, blood pressure was higher in patients than subjects, it was associated with reduced endothelial dependent vasodilation, C.reactive protein was higher in CAD patients and also was associated with decreased endothelial dependent vasodilation. Conclusion: Healthy subjects show diurnal rhythm in endothelial function manifested by increase in endothelial dependent vasodilation in morning time, a process which may counter act other potentially adverse factors which occur at this time, CAD patients showed loss of this protective mechanism, a process which may aid in explanation of morning increase in incidence of acute coronary syndromes.