© 1995 by European Society of Cardiology
Copyright © 1995, European Society of Cardiology
The pressure-flow relation in the canine coronary artery: combined effects of critical stenosis and intracoronary thrombosis
aAcademic Unit of Cardiovascular Medicine, Charing Cross & Westminster Medical School, Fulham Palace Road, London W6 8RF, UK
bMedical Physics, Faculty of Medicine, University of Amsterdam, Amsterdam, Netherlands
* Corresponding author, present address: University Department of Cardiac Surgery, 16 Alexandra Parade, Glasgow G31 2ER, UK. Tel. (+ 44-141)304-4730; Fax: (+ 44-141)552-0987.
Objective: To characterise the effect of coronary intra-arterial thrombosis upon the downstream vascular bed. Background: The vascular response downstream from a coronary intra-arterial thrombus has not previously been characterised. We postulated that downstream vasoconstriction might result from the presence of endothelial damage with consequent growth of platelet-rich thrombus. Methods: We measured the pressure gradient and flow across, and the pressure/flow ratio distal to, a canine left circumflex artery stenosis with and without endothelial damage causing intracoronary thrombosis. We also observed the effects of transient complete occlusions. Results: At occlusion, the pressure gradient was maximal; relief of occlusion caused a rapid increase flow and distal pressure with a rapid decrease in stenosis pressure gradient and resistance. Subsequently there was a period of stable stenosis resistance with pressure gradient and flow declining; distal pressure therefore increased at this time. Finally in the thrombus group only, stenosis resistance increased again towards re-occlusion. During occlusion, distal pressure averaged 49 ± 18 mmHg in the presence of thrombus vs. 22 ± 4 mmHg in its absence (P < 0.001). Following release of occlusion, the flow increased faster than distal pressure, so that the ratio (distal pressure/flow) fell rapidly. Subsequently, distal pressure continued to increase after flow had reached a peak and begun to decline, suggesting vasoconstriction. In the presence of thrombus, the distal pressure/flow ratio was higher than in the absence of thrombus, both at maximal vasodilatation (P < 0.005) and at maximum vasoconstriction (P < 0.025). Conclusions: During cyclic flow variations the stenosis resistance changes are exactly as expected from thrombus growth and embolisation. The distal pressure/flow ratio showed a time-dependent increase which appeared greater when conditions favoured intracoronary thrombosis.
KEYWORDS Dog, coronary artery; Thrombosis; Platelets; Coronary blood flow
1 Professor MIM Noble is the Weston Professor of Cardiovascular Medicine and is supported by the Garfield Weston Trust, London, UK.
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