EFFECTS OF BRAIN (B-TYPE) NATRIURETIC PEPTIDE ON CORONARY-ARTERY DIAMETER AND CORONARY HEMODYNAMIC VARIABLES IN HUMANS - COMPARISON WITH EFFECTS ON SYSTEMIC HEMODYNAMIC VARIABLES

Objectives. This study attempted to clarify the effects of human brain (B-type) natriuretic peptide on coronary artery diameter and coronary vascular resistance in humans. Background. Brain natriuretic peptide induces vasodilation in systemic circulation by activating particulate guanylate cyclase of the vascular smooth muscle. Methods. In 13 patients with normal coronary arteries and left ventricular function, brain natriuretic peptide was infused at 0.5 mu g/kg body weight per min for 4 min into the left main coronary artery (six patients, Group A) or into the pulmonary artery (seven patients, Group B). Systemic hemodynamic variables and coronary sinus blood flow were measured before and after the infusion. The lumen diameter of the left coronary artery was quantitatively measured. Results. In both groups, brain natriuretic peptide significantly increased heart rate and decreased mean arterial pressure. Rate-pressure product remained unchanged in bath groups. Brain natriuretic peptide decreased systemic vascular resistance index significantly in both groups (both p < 0.01 vs. baseline), and there was no difference in the effect between the groups. Brain natriuretic peptide decreased coronary vascular resistance in Group A (p < 0.01 vs. baseline) but did not affect coronary vascular resistance in Group B (p < 0.01 vs. Group A). The lumen diameters of the proximal and distal segments of the left coronary artery were increased significantly after brain natriuretic peptide in both groups. After infusion of brain natriuretic peptide, mean plasma level of brain natriuretic peptide in the coronary sinus increased from 36 to 130,411 pg/ml in Group A and from 64 to 12,329 pg/ml in Group B. Conclusions. Brain natriuretic peptide shows a vasodilator effect on the coronary artery system in humans. However, the effect does not appear uniformly but is seen preferentially in the epicardial coronary artery. The sensitivity of the coronary resistance vessels to brain natriuretic peptide is low compared with that of the resistance vessels of the systemic circulation.