An in-vitro model of coronary artery stenosis: influence of stenosis morphology on velocity measurements

Guide-wire mounted Doppler velocity probes for intracoronary use permit to study the hemodynamic consequences of coronary lesions in patients with coronary artery disease. To investigate the impact of stenosis morphology and stenosis severity on measurements of flow velocity, the authors performed in-vitro experiments in an in-vitro model using plastic tubes with a 3 mm diameter and 56%, 75% and 89% area stenoses. Steady state volumetric flow was varied between 0.5 and 2.0 ml/s and measurements of peak Doppler velocity were obtained for different configurations of stenosis geometry (1 to 20 mm length, smooth and abrupt interfaces). In the poststenotic region (up to 2 cm), consistent velocity measurements could not be obtained probably due to perturbations in the flow profile. The relation between average velocity (Va, cm/s) and peak velocity (Vp, cm/s), was linear proximal to the stenosis (Va=0.8 Vp-0.7, r=0.98 p<0.01.). Within the stenosis the relationship was similar however the 1 mm long, 89% stenoses displayed a slightly different relation with a steeper slope. The ratio of peak and average velocities was significantly different from 0.5 indicating that the velocity profile in steady flow conditions is not parabolic. Estimation of stenosis severity based on the continuity equation was accurate for all model stenoses and independent of morphology and flow rate. These observations provide important information for the clinical application of intracoronary probes measuring flow velocity