Influence of the chosen model of stenosis on pressure-flow relationships in isolated perfused arteries.
Passive changes in luminal diameter caused by a fall in the intravascular distending pressure at the site of a severe coronary artery stenosis were recently proposed as a possible cause of transient myocardial ischaemia. We tested this hypothesis in 5 dog carotid arteries perfused with blood at a constant inflow (100 mm Hg) and variable outflow pressures (40-0 mm Hg). Similar degrees of stenosis were induced either with an external circumferential snare or with an intravascular fluid-filled balloon catheter. In 39 experiments outflow pressure was progressively decreased from 40 to 0 mm Hg. This was done first in the absence of stenosis, secondly with an external stenosis (snare) and finally with an internal stenosis of comparable severity (fluid-filled balloon). When stenosis was absent or intraluminal, flow increased progressively from 109.1 +/- 39 to 136 +/- 55 ml/min (P less than 0.06) and from 23 +/- 16 to 34.2 +/- 16 ml/min (P less than 0.001), respectively. Resistance also rose because flow increased proportionally less than the pressure gradient. Conversely, when stenosis was produced by a snare, flow decreased progressively, from 23.9 +/- 17 to 10.7 +/- 15 ml/min (P less than 0.001). Assuming the reduction of flow was caused by the external stenosis compressing the wall into the lumen (against the intravascular pressure) we prepared an artificial vessel with a foam rubber wall inside a silastic tubing. In this artificial vessel (but not in a glass model) a snare stenosis caused reduction in flow when outflow pressure was lowered. Passive changes in caliber due to a reduced distending pressure do not therefore appear to be a cause of flow reduction.
D000818:Animals; D001157:Arterial Occlusive Diseases / Q000503:physiopathology*; D006328:Cardiac Catheterization; D002339:Carotid Arteries / Q000503:physiopathology; D003326:Coronary Circulation; D003327:Coronary Disease / Q000209:etiology / Q000503:physiopathology*; D004195:Disease Models, Animal; D004285:Dogs; D008955:Models, Cardiovascular; D010477:Perfusion; D011312:Pressure