Intraoperative coronary collateral function in patients with coronary occlusive disease. Nitroglycerin responsiveness and angiographic correlations.

SUMMARY To elucidate the direct influence of nitroglycerin on coronary collateral function in patients and to clarify the relation between angiographic appearance and functional peiformance 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 pre-operative 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. Additional Indexing Words: Myocardial ischemia Coronary arteriography T HE ROLE OF CORONARY collateral channels in the pathophysiology of coronary artery disease has been uncertain.' This uncertainty is related, at least in part, to the lack of a direct assessment of coronary collateral function in humans. Radioisotope techniques have led to important advances in the evaluation of regional myocardial blood flow.2-8 However, changes in regional perfusion are not necessarily the result of 298 Vasodilator Coronary bypass graft alterations in coronary collateral function; many other factors are capable of influencing the distribution of myocardial blood flow. Angiographic and postmortem descriptions of coronary collateral anatomy frequently have been used to make inferences concerning the functional performance of coronary collateral channels.9-13 Yet these anatomic findings have not been previously correlated with physiologic function. In particular, angio-graphic assessment of coronary collaterals, an important part of the clinical evaluation of symptomatic coronary disease, has not been systematized by an objective, generally applicable grading system, nor have angiographic findings been compared with independently …