Synergistic relation between vasoconstriction and fixed epicardial vessel stenosis in coronary artery disease.

The clinically important hemodynamic consequences of epicardial coronary artery vasoconstriction were examined in the presence of stenosis of major vessels. For this purpose, a special isolated canine circumflex coronary artery preparation was used to provide elimination of reflex, humoral, and distal coronary vasculature resistance influences. Without stenosis, active vasoconstriction induced by either phenylephrine (10-3 M), angiotensin (10-5 M), or acetylcholine (10-5 M) had no effect on flow through the circumflex artery. Coronary arterial stenosis was created by intraluminal obstruction, which itself produced only insignificant effect on vessel flow. When the vasoconstrictor agent stimulation was superimposed on the fixed underlying vascular stenosis, there occurred dose-dependent marked flow decreases through the partially obstructed vessel accompanied by major trans-stenotic pressure gradient increases. Phenylephrine, angiotensin, and acetylcholine separately caused significant (54%, 59%, and 46%) flow decreases with 48, 54 and 50 mm Hg pressure gradient increases respectively. This study demonstrates that vasoconstriction and stenosis act synergistically to reduce flow through obstructed major vessels in coronary artery disease.