Ilan A Yaeger
Background: The multi-artery fractional flow reserve (FFR) method takes into account stenosis-stenosis interaction often encountered in some configurations of coronary multi vessel disease (MVD) scenarios. The multi-artery FFR formulas of actual FFR (FFRreal) are in principle dependent not only on stenosis but also on the relative microvascular resistances of the involved end-arteries and may therefore vary from one patient to another, compromising the practicability of the method.
Objectives: In this article the possible effect of relevant microvascular resistances on the numerical multi-artery FFR values is explored in order to assess the practicability of the multi-artery FFR method.
Methods: A basic ad-hoc model of the coronary microvasculature is proposed and a quantitative relationship between the epicardial arterial morphology and the associated microvascular resistance is established.
Results: It turns out that in stenotic 3-artery configurations of sizable coronary arteries (LMCA, LAD, LCx, RCA and occasionally sizable D1, M1 etc.), in examples within ordinary statistical variation of morphology, multi-artery FFR exhibits acceptable variations of just ± 0.02 in the low and intermediate stenosis severity ranges. The multi-artery FFR proves useful also in arterial (sizable)'mother'-(small) 'daughter' relationships, yielding very simple pressure-ratio formulas for FFRreal of each artery.
Conclusions: In the low and intermediate stenosis severity ranges, morphological statistical variations (from patient to patient) do not affect significantly the multiartery FFRreal values in stenotic 3-artery configurations of sizable coronary arteries as well as in (sizable)'mother'-(small)'daughter' configurations. The multi-artery FFR method can be therefore applied reliably in such cases, yielding correct FFRreal numerical results.
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