Abstract

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 (FFR^real) 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 FFR^real 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 FFR^real 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 FFR^real numerical results.