1. Fig. 2. Concept of fractional flow reserve
Fig. 2. Concept of fractional flow reserve. Fractional flow reserve (FFR) is defined as ratio of maximal coronary blood flow in diseased artery (Q max s  Qsmax ) to normal maximal coronary blood flow in same artery (Q max n  Qnmax ). As venous pressure (Pv) is negligible compared to aortic (Pa) and distal coronary pressure (Pd), FFR can be calculated as ratio of Pd and Pa.
Korean J Radiol May-Jun;17(3):