Hemodynamics of coronary artery stenosis

A model is proposed to study the hemodynamics of various types of coronary stenosis. The model coronary artery is assumed to be an elastic tapered tube. A progressive degree of concentric and eccentric stenoses are studied. Measured pulsatile coronary pressure, flow, and intramyocardial pressure are used as input data to calculate the pressure and flow velocities at different locations of the artery. The simulation yields results that agree well with published data in dog experiments, and those from human stenotic coronary arteries. The present model shows that in a cardiac cycle, the overall hydraulic resistance owing to a specific stenosis tends to be flow independent at low flow rate but increases linearly with flow at higher coronary flow. This flow independent resistance increases with progressive stenosis. At low flow, the mean coronary flow in a cardiac cycle is relatively constant with stenoses up to 80%, but decreases dramatically with further increase in the degree of narrowing. At high resting flow rate, this mean flow is markedly reduced at much smaller degrees of constriction. The simulated pressure velocity relation of poststenotic dilatation indicates an additional pressure loss at the distal end of the stenosis, but the calculated resistance to flow is actually lessened. While stenosis length increases pressure loss and resistance to flow, its effect on mean flow appears disproportionally insignificant. Eccentric lesions appear to be more detrimental than concentric ones as they produce additional pressure loss and greater resistance across the coronary artery lesion.