BackgroundOur study compares the effect of acute proximal stenosis of a coronary artery supplying a myocardial perfusion bed with that of stenosis of an adjacent artery resulting in collateral flow diversion supplied by the same perfusion bed. These alterations in coronary physiology were quantified by digital angiographic impulse response analysis of contrast material mean transit time for the coronary microcirculation, Tmicro, and by flowmeter and microsphere assessment of flow and regional flow distribution.Methods and ResultsIn 25 open-chest, anesthetized dogs, progressive circumflex artery stenosis led to a concordant decrease of circumflex artery resting and hyperemic flow, coronary flow reserve, and inverse angiographic mean transit time Tmicro−1(P< .01). Progressive left anterior descending artery stenosis led to no or only minor changes of circumflex artery resting or hyperemic flow or flow reserve; only occlusion induced a significant decrease of coronary flow reserve (from 4.0±0.7 to 3.2±0.5,P< .05), whereas resting flow was in-creased by +8.6±5.9%. In contrast, circumflex artery Tmicro−1diminished significantly with critical left anterior descending artery stenosis and occlusion (from 16.7±4.2 to 12.6±2.2[P< .05] and 12.0±3.0 min−1[P< .01], respectively). In 8 dogs, collateral flow induced by left anterior descending artery occlusion was quantified by microsphere injections. The decrease of circumflex artery Tmicro−1correlated with the magnitude of collateral flow (r= .76) and was associated with theangiographic extent of collateral filling.ConclusionsDigital angiographic impulse response analysis is a sensitive method to detect the influence of proximal artery stenosis on an artery's myocardial perfusion bed as well as the changes induced by an adjacent artery stenosis inducing collateral flow diversion from the supplying myocardial perfusion zone.