Synergistic effects of pressure, distal resistance, and vasoconstriction on stenosis.

The synergistic effects of perfusion pressure, distal resistance, and arterial vasoconstriction on stenotic hemodynamics were examined using an in vitro arterial preparation. Canine carotid and coronary arteries were attached to a perfusion apparatus. Perfusion pressure and distal resistance were controlled independently. Arterial vasoconstriction was induced by perfusing the artery with a 100 mM K solution. A stenosis was created by partially inflating a balloon catheter within the artery. Pressure proximal and distal to the arterial segment and flow were measured. For the coronary arteries the combination of high perfusion pressure, high distal resistance, and arterial vasodilation decreased stenotic resistance to 0.79 +/- 0.10 mmHg . ml-1 . min, whereas low perfusion pressure, low distal resistance, and arterial vasoconstriction increased stenotic resistance to 22.40 +/- 4.90 mmHg . ml-1 . min (P less than 0.01). These large changes in stenotic resistance were accompanied by maximum and minimum flow rates of 86.1 +/- 6.0 and 5.5 +/- 1.1 ml/min, respectively (P less than 0.01). Qualitatively similar results were obtained with the carotid arteries. Thus perfusion pressure, distal resistance, and arterial vasoconstriction acted synergistically to greatly influence the severity of the stenosis.