Intracoronary endothelin receptor blockade improves endothelial function in patients with coronary artery disease

Endothelin (ET)-1 receptor blockade improves endothelial function in the forearm of patients with atherosclerosis. The aim was to investigate whether intracoronary ET receptor blockade improves coronary endothelial function and increases blood flow in patients with coronary artery disease. Ten patients received a 60-minute infusion of either the selective ETA receptor antagonist BQ123 (40 nmol/min, n = 6) or BQ123 + the ETB receptor antagonist BQ788 (40 nmol/min, n = 4). In all patients, substance P, an endothelium-dependent vasodilator, did not increase baseline coronary flow reserve with thermo dilution (CFRThermo) (0.71 +/- 0.14 s during NaCl versus 0.59 +/- 0.14 s during substance P) or baseline quantitative coronary angiography (QCA) (2.74 +/- 0.16 mm versus 2.83 +/- 0.20 mm). After ET receptor blockade, however, the response to substance P was significantly improved as determined both by CFRThermo (0.62 +/- 0.14 s during NaCl versus 0.48 +/- 0.10 s during substance P, p < 0.05) and by QCA (2.70 +/- 0.18 mm versus 2.85 +/- 0.19 mm, p < 0.05). In addition, ET blockade increased blood flow in all patients by 16% +/- 10% (n = 10, p < 0.05) and in the BQ123 group by 22% +/- 16% (n = 6, p < 0.05). Furthermore, ETA blockade increased blood flow significantly more than did dual ETA/ETB blockade (p < 0.05). These findings indicate that ET receptor blockade may be a new therapeutic strategy to improve coronary vascular function in patients with coronary artery disease.