Is there functional collateral flow during vascular occlusion in angiographically normal coronary arteries?

Background - Thus far, it is unknown whether there is functional collateral flow through preexisting anastomoses in patients with angiographically normal coronary arteries. Such preformed coronary collateral vessels could form the basis for subsequently developing protective natural bypasses in the presence of coronary artery disease. Methods and Results - Among 100 patients, the collateral flow index (CFI) was measured in coronary arteries without stenotic lesions. The CFI was determined by simultaneous measurement of mean aortic pressure, central venous pressure, and coronary wedge pressure via a sensor-tipped guidewire at the end of a 1-minute balloon occlusion. Patients were divided in 2 groups according to complete angiographic absence ( 51 patients) or partial presence ( 49 patients) of stenotic lesions in coronary arteries other than that undergoing collateral measurement. CFI in all patients ( 61 +/- 10 years; men/women, 69/31) amounted to 0.18 +/- 0.08 ( range, 0.04 to 0.36). It showed a normal Gaussian frequency distribution; 22 individuals had a CFI greater than or equal to 0.25, a value that was empirically found to represent well-developed collaterals protective against myocardial ischemia during coronary occlusion. Accordingly, 17 patients did not reveal signs of myocardial ischemia during coronary balloon occlusion, as assessed from an intracoronary ECG, and 26 patients did not experience angina pectoris during occlusion. Conclusion - In humans with angiographically normal coronary arteries, there are functional collateral vessels to the extent that one fifth to one quarter of them do not show signs of myocardial ischemia during brief vascular occlusions.