Strategies of Handling a Stenotic Unprotected Left Main Coronary Artery by Multi-Artery Fractional Flow Reserve Method

Background and aims: By present guidelines, unprotected stenotic LMCA that requires revascularization is revascularized in most cases by a coronary artery bypass graft (CABG) operation whereas only select groups of patients that are contraindicated for CABG operation are treated by percutaneous transluminal coronary angioplasty (PTCA). A possibility of a CABG operation is never taken lightly, therefore ways of avoiding it within the LMCA-LCx-LAD stenotic configuration are explored in this article.

Methods and results: A numerical simulation of intracoronary pressures combined with the multi-artery FFR method is applied to the stenotic 3-artery configuration LMCA-LCx-LAD under conditions of stable and minimal microvascular resistance. In this method a clear distinction is made between the familiar FFR^true which is the FFR of an artery in its virtually stand-alone position and its actual FFR (denoted FFR^real) when the artery is part of an arterial configuration in which the stenosis-stenosis interaction with other arteries impedes and reduces its blood flow (and therefore FFR^real ≤ FFR^true ). The kind of treatment that the artery needs is now determined by its FFR^real numerical value, not by its FFR^true. From the initially measured intracoronary pressures the method can yield the current status of the LMCA-LCx-LAD configuration (namely FFR^real and FFR^true of each artery). Also, from the very same data, outcomes of all possible future revascularizations can be predicted. From the predicted future outcomes one can figure out if LMCA revascularization is required and also what effect would a LMCA revascularization, or lack of it, have on the current treatment decision for LCx and/or LAD arteries. The numerical examples in the article clearly show the interdependence of treatment decisions for the various arteries through inter-arterial stenosis-stenosis interactions. It turns out that in the intermediate stenosis severity range the FFR^true of an artery may be satisfactory but its FFR^real is sometimes lower by about 0.3 indicating in most of such cases that revascularization is mandatory.

Conclusion: The first step in the multi-artery FFR method is to measure the intracoronary pressures at particular locations in the arterial configuration. The intracoronary pressures yield the present status of the configuration as well as the outcomes of all possible future revascularizations of the arteries of the configuration (provided that no revascularization-induced stenosis anatomy changes take place). This unique property yields eventually the optimal resolution of the stenotic LMCA-LCx-LAD configuration.

Keywords: Fractional flow reserve; Multi-artery fractional flow reserve; Percutaneous coronary intervention