Impairment of coronary flow reserve in aortic stenosis

Abstract

Coronary flow reserve (CFR) is markedly reduced in patients with severe aortic valve stenosis (AS), but the exact mechanisms underlying this impairment of CFR in AS remain unclear. Reduced CFR is the key mechanism leading to myocardial ischemia symptoms and adverse outcomes in AS patients. The objective of this study was to develop an explicit mathematical model formulated with a limited number of parameters that describes the effect of AS on left coronary inflow patterns and CFR. We combined the mathematical V(3) (ventricular-valvular-vascular) model with a new lumped-parameter model of coronary inflow. One thousand Monte-Carlo computational simulations with AS graded from mild up to very severe were performed within a wide range of physiological conditions. There was a good agreement between the CFR values computed with this new model and those measured in 24 patients with isolated AS (r = 0.77, P < 10(-4)). A global sensitivity analysis showed that the valve effective orifice area (EOA) was the major physiological determinant of CFR (total sensitivity index = 0.87). CFR was markedly reduced when AS became severe, i.e., when EOA was <1.0 cm(2), and was generally exhausted when the EOA was <0.5-0.6 cm(2). The reduction of CFR that is associated with AS can be explained by the concomitance of 1) reduced myocardial supply as a result of decreased coronary perfusion pressure, and 2) increased myocardial metabolic demand as a result of increased left ventricular workload.

Prosthesis-Patient Mismatch: An Update

“…Accordingly, Garcia et al [31] have reported that when the aortic valve indexed EOA is larger than 0.8 to 0.9 cm 2 /m 2 , there is no significant impact on CFR which decreases sharply when the indexed EOA is lower than this threshold and becomes almost completely exhausted when the indexed EOA is below 0.5 cm 2 /m 2 .…”

Impact of Left Ventricular Afterload on Longitudinal Dyssynchrony in Patients With Severe Aortic Stenosis and Preserved Ejection Fraction

“…21, 22 Furthermore, longitudinal function is governed by the subendocardial myocardial fibers, which are aligned longitudinally and more sensitive to microvascular ischemia. 12, 23 The selective impairment in longitudinal function in patients with AS is thus related to the increase in subendocardial stress and associated reduction in coronary flow reserve. Consequently, the improvement in coronary flow reserve after AVR, secondary to an increase in the effective orifice area, results in a more efficient myocardial arterial supply and improved longitudinal function.…”

Summarization of long-term prognostic significance of coronary flow reserve in special disorders (SZEGED Study)

“…It is known that angina pectoris, myocardial ischaemia, inadequate left ventricular hypertrophy, smaller coronary artery dimensions and reduced coronary flow reserve occur in most of AS patients (5,(10)(11)(12)(13)(14)(15)(16). The reduction of coronary flow reserve that is associated with AS can be explained by the concomitant presence of reduced myocardial supply as a result of decreased coronary perfusion pressure, and increased myocardial metabolic demand as a result of increased left ventricular workload (16).…”

“…The reduction of coronary flow reserve that is associated with AS can be explained by the concomitant presence of reduced myocardial supply as a result of decreased coronary perfusion pressure, and increased myocardial metabolic demand as a result of increased left ventricular workload (16). CFR was found to be similarly decreased in AS patients with and without severe left anterior descending coronary artery (LAD) disease (17).…”