Functional significance of coronary collateral vessels in patients with coronary artery disease.

Regional myocardial perfusion was measured in 12 normal subjects and in 34 patients with coronary artery disease (CAD) at rest and during infusion of isoproterenol. Increments in regional flows normalized for change in heart rate-systolic product were 91 +/- 28% (S.D.) in normals, 71 +/- 44% in normal regions in diseased hearts, 58 +/- 33% in regions supplied by 50% to 70% stenosed arteries, 35 +/- 32% in regions supplied by arteries stenosed by more than 70%, and 16 +/- 27% in regions supplied by collateral vessels only. In 3 of 14 regions perfused entirely via collateral pathways, regional perfusion decreased with isoproterenol. Therefore the extent to which coronary flow reserve estimated with isoproterenol was compromised varied directly with the severity of anatomic coronary artery lesions and, in some regions entirely perfused by collateral vessels, an increase in heart rate-systolic pressure product was accompanied by a decrease in perfusion below resting levels. It is concluded that collateral vessels effectively maintain flow rates at normal levels at rest but tend to be inefficient at delivering blood when myocardial oxygen demand is increased.