Intraoperative Coronary Collateral Function in Patients With Coronary Occlusive Disease

Abstract

To elucidate the direct influence of nitroglycerin on coronary collateral function in patients and to clarify the relation between angiographic appearance and functional performance of coronary collaterals, we measured retrograde flow and peripheral coronary pressure (PCP) before and after nitroglycerin in patients undergoing saphenous vein bypass. Measurements were made via the distally (but not proximally) attached vein graft while the coronary artery receiving the graft was totally occluded proximal to the site of graft attachment. Nitroglycerin (100 to 150 mcg bolus and 100 mcg/min) was infused into the ascending aorta in 29 patients. Baseline measurements revealed: aortic pressure mean 79 mm Hg, PCP 30 mm Hg, retrograde flow 2.7 ml/min, and collateral resistance 28.5 mm Hg/ml/min. Following nitroglycerin, mean aortic pressure decreased 18% but retrograde flow was not consistently changed; thus collateral resistance fell significantly (average 28%, P < 0.05). Similarly, collateral resistance fell (mean 50%) in eight individuals in whom aortic pressure changes were attenuated by altering systemic flow. If calculated as a fraction of aortic pressure, PCP increased 9.9% (P < 0.02), a finding consistent with enhanced collateral flow. Our results suggest that nitroglycerin can diminish resistance to collateral flow despite severe multivessel involvement. Comparison of baseline data with preoperative angiography revealed a correlation between the size and extent of coronary collaterals and physiologic evidence of collateral function. Thus, angiographic appearance of coronary collaterals accurately predicts collateral function during bypass surgery.