Does variation in hemodynamic conditions affect fractional flow reserve (FFR) in a resistive model of epicardial stenosis?
Computational modeling demonstrates that fractional flow reserve (FFR) is dependent on hemodynamic conditions such as aortic pressure and microvascular resistance, challenging the assumption of its independence.
Pressure-based fractional flow reserve (FFR) is used clinically to evaluate the functional severity of a coronary stenosis, by predicting relative maximal coronary flow (Q s /Q n ). It is considered to be independent of hemodynamic conditions, which seems unlikely because stenosis resistance is flow dependent. Using a resistive model of an epicardial stenosis (0–80% diameter reduction) in series with the coronary microcirculation at maximal vasodilation, we evaluated FFR for changes in coronary microvascular resistance ( R cor = 0.2–0.6 mmHg · ml −1 · min), aortic pressure (P a = 70–130 mmHg), and coronary outflow pressure (P b = 0–15 mmHg). For a given stenosis, FFR increased with decreasing P a or increasing R cor . The sensitivity of FFR to these hemodynamic changes was highest for stenoses of intermediate severity. For P b > 0, FFR progressively exceeded Q s /Q n with increasing stenosis severity unless P b was included in the calculation of FFR. Although the P b -corrected FFR equaled Q s /Q n for a given stenosis, both parameters remained equally dependent on hemodynamic conditions, through their direct relationship to both stenosis and coronary resistance.
Siebes et al. (Tue,) studied this question.
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