Effect of artery curvature on the coronary fractional flow reserve

Understanding the effect of the artery curvature on the pressure drop inside the arteries is of great importance due to the existence of several curved portions inside the coronary arterial system. In this paper, an experimental model is developed to account for the effect of the curvature of the coronary arteries on the pressure drop and Fractional Flow Reserve (FFR). FFR is an index for the evaluation of the functional significance of coronary stenosis and is defined as the ratio of the coronary pressure downstream of the stenosis to its upstream value. To measure the pressure drop and FFR across curved artery models, three-dimensional-printed curved artery models are fabricated and installed in the test section of the experimental rig. For ratios of curvature radius over the artery diameter ranging from 2 to 7, there are a minimum value for the pressure drop and, hence, a corresponding maximum value for FFR at a ratio of approximately 3. For the curved arteries with larger curvature radii, the pressure drop increases, and consequently, FFR decreases with an increase in the radius. The results showed that an accurate evaluation of the pressure drop and FFR inside a curved coronary artery can only be achieved by accounting for the effect of curvature parameters including the curvature angle and radius, such that neglecting the effect of the artery curvature results in an underestimation of the pressure drop by about 25%–35%. The developed equation is able to determine the pressure drop inside a curved coronary artery model noninvasively.