Pharmacoangiographic evaluation of the hemodynamic significance of coronary artery stenoses.

Acute stenoses of varying degree were produced in the circumflex arteries of 5 calves, and chronic stenoses which reduced blood flow by about 50% were effected in the left anterior descending coronary arteries of 14 dogs. Selective vasodilators or amyl nitrite increased blood flow more than 100% in nonstenotic arteries, but less in stenotic ones. Increased transstenotic blood flow was associated with an increased pressure gradient and increased frequency of collateral circulation. Collateral circulation was sometimes recognizable when the pre- and postvasodilatory angiograms were compared but not when the angiograms were examined individually. The altered flow patterns demonstrated by comparative studies may be a very sensitive index of collateral circulation.