Endothelin Levels in Patients with Cardiac Syndrome X at Rest and Exercise

We aimed to determine plasma endothelin levels in patients with cardiac syndrome X at rest and exercise, as compared to healthy subjects. Plasma endothelin-1 concentrations were measured in 30 patients with cardiac syndrome X (group A) at rest and after peak exercise, as compared to 14 healthy control subjects (group B) who were in a similar age group. ELISA method was used for the measurement of ET-1 levels. Coronary angiograms were normal in all patients and the control group. Symptom-limited maximal treadmill exercise tests with Bruce protocol were found positive in all patients with syndrome X. Exercise tests were normal in the control group. Results: In patients with cardiac syndrome X, plasma endothelin-1 levels were found significantly elevated either during rest or after peak exercise when compared with the control group (2.52±1.6 pg/ml, 1.38±1.8 pg/ml, p<0.001, 3.68±1.1 pg/ml, 1.37±0.2 pg/ml, p<0.001 respectively). In patients with cardiac syndrome X, plasma endothelin-1 levels after peak exercise were found significantly higher than at rest (3.68±1.1 pg/ml 2.52±1.6 pg/ml, p<0.001). No significant difference (p=0.17) existed between plasma endothelin-1 levels during rest and after peak exercise in the control group. It may be concluded that ET-1 increase has an important role in the pathogenesis of the cardiac syndrome X. ECG changes and exertional angina in these patients can be related to increase in plasma ET-1 levels.