Effects of intracoronary infusion of atrial natriuretic peptide on pacing-induced myocardial ischemia in patients with effort angina pectoris.

Background: Atrial natriuretic peptide (ANP) has been shown to dilate the coronary artery. The aim of this study was to determine whether, in patients with effort angina pectoris, intracoronary infusion of ANP attenuates pacing-induced myocardial ischemia either by dilating the stenotic lesion in a large coronary artery or by dilating collateral vessels.

Methods: We studied six patients who had total or subtotal occlusion in one coronary artery and well-developed, angiographically visible collateral vessels (group A) and five patients who had a significant stenosis in a large coronary artery with no visible collateral vessels (group B). Their heart rate was increased by atrial pacing both before and after intracoronary infusion of ANP (0.03 microgram/kg/min for 15 min) into the donor artery of collateral vessels in group A or into the stenotic artery in group B.

Results: Before ANP infusion, all patients of both groups developed an ischemic ST-segment depression (> or = 0.1 mV) and angina-like chest pain from pacing tachycardia. After ANP infusion, significant ST-segment depression was induced by rapid pacing in only one out of six patients of group A, whereas it was noted in all patients of group B (P < 0.01). After ANP infusion, chest pain developed in one out of six patients in group A, whereas it appeared in four out of five patients in group B (P < 0.05). ANP significantly dilated the angiographically normal segment of the epicardial coronary artery, but it did not significantly change the severity of the stenotic lesion in either group. ANP did not change the basal arterial pressure or heart rate, nor did it change their response to pacing tachycardia.

Conclusions: Infusing ANP into the donor artery of collateral vessels, but not into the artery with culprit stenotic lesion, attenuated pacing-induced myocardial ischemia. Therefore, the beneficial effects of ANP in reducing pacing-induced myocardial ischemia may result from the increase in myocardial perfusion to the ischemic area caused by dilating the collateral vessels.