FLUID-DYNAMICS OF A PARTIALLY COLLAPSIBLE STENOSIS IN A FLOW MODEL OFTHE CORONARY CIRCULATION

The influence of passive vasomotion on the pressure drop-pow (Delta P- Q) characteristics of a partially compliant stenosis was studied in an in vitro model of the coronary circulation. Twelve stenosis models of different severities (50 to 90 percent area reduction) and degrees of flexible wall (0 to 1/2 of the wall circumference) were inserted into thin-walled Inter tubing and pressure and pow data were collected dur ing simulated cardiac cycles. In general, the pressure drop increased with increasing fraction of flexible wall for a given flow rate and st enosis severity. The magnitude of this effect was directly dependent u pon the underlying stenosis severity. The diastolic Delta P-Q relation ship of severe, compliant models exhibited features of partial collaps e with an increase in pressure drop at a decreasing flow rate. It is c oncluded that passive vasomotion of a normal wall segment at all eccen tric stenosis in response to periodic changes in intraluminal pressure causes dimensional changes in the residual lumen area,which can stron gly affect the hemodynamic characteristics of the stenosis during the cardiac cycle. This mechanism may have important implications for the onset of plaque fracture and the prediction of the functional signific ance of a coronary stenosis based on quantitative angiogram analysis.