Comparison of endothelin-1 levels at rest and during exercise between patients with cardiac syndrome-X and healthy people

: Several previous studies have shown that endothelin-1 (ET 1) plasma levels are raised in cases of endothelial abnormality and microvascular dysfunction. Syndrome-X constitutes an important clinical entity characterized by angina-like pain and normal coronary arteries which is believed to reflect microvascular dysfunction. The aim of the present study was to investigate the role of ET 1 in the pathophysiology of the above syndrome. For that purpose the plasma ET 1 concentrations, measured by radioimmunoassay, between 28 X-syndrome patients (group A) and 10 age-matched normal control subjects (group B) at rest and at the peak of the exercise testing were compared. We specify that all individuals of group A were referred to our Department for effort angina and were found to have normal coronary arteriograms, negative ergonovine and hyperventilation test and positive exercise test. Our results showed that while at rest ET 1 plasma concentrations did not differ significantly between the two groups, at the peak of the exercise test its levels were found to be significantly higher in syndrome-X patients as compared with those of normal subjects (p< 0.001). In addition, in healthy control subjects ET 1 levels decreased during exercise as compared with the baseline values and that difference was found to be statistically significant (p approximately 0.01). The above finding suggests opposite kinetics during exercise of ET 1 between the two groups studied, which could explain effort angina onset in patients with syndrome-X.