Effect of simulated hyperemia on the flow field in a mildly atherosclerotic coronary artery casting of man.

The purpose of this investigation was to determine changes in the flow field due to mild atherosclerosis using a main coronary artery casting of man with maximum obstruction of about 50% by area. Local pressure changes were measured using six pressure tap holes drilled flush to the wall along the casting. The test fluid used was a 33% sugar-water solution to simulate the viscosity of blood. Flow visualization results were obtained by injecting blue dye slowly through the pressure tap holes. The local pressure measurements clearly demonstrated a significant Reynolds number effect. At physiological Reynolds numbers of 80-710, a local pressure rise was observed downstream of the mild atherosclerotic constriction of 50% because of momentum changes. The flow visualization study indicated that the critical Reynolds number for flow separation to occur in the divergent region of this coronary casting was about 330. Flow separation has been implicated in the genesis of atherosclerosis but there is little information on the extent of flow separations in vivo in arteries of man. These results are believed to be important in obtaining a quantitative relation between coronary morphology and the fluid dynamic consequences of mild diffuse disease especially under conditions of maximum cardiac demand i.e., higher coronary flow rates, and thus Reynolds numbers associated with space and/or atmospheric flight.