Mathematical model of pressure-related changes in coronary diameter and their effect on the assessment of coronary flow velocity reserve

The authors used a theoretical analysis to test the hypothesis that flow velocity measurements distal to a stenosis would result in a coronary flow velocity reserve (CFVR) that is artificially enhanced because of changes in distal arterial dimensions between resting and hyperemic flow conditions. The results of this model suggest that passive reduction of coronary artery diameter distal to a stenosis in response to reduced intraluminal distending pressures during elevated flow conditions may introduce a significant overestimation of distal CFVR. The pressure-dependent changes in distal diameter may cause poststenotic velocities to be disproportionately higher and coronary flow velocity reserve then no longer represents volume flow reserve. A cut-off value of CFVR < 2 has been found in humans to successfully identify coronary lesions that can lead to reversible ischemia as determined by noninvasive stress tests. For the more severe stenosis models in this simulation, this threshold value was crossed when comparing proximal and distal values for CFVR. While it is not known to what degree this pressure-dependent diameter reduction exists in humans, it is possible that erroneous assessments of the physiological significance of a coronary stenosis may occur in current clinical practice