Influence of zero flow pressure on fractional flow reserve.
Fractional flow reserve (FFR) is a commonly used index to assess the functional severity of a coronary artery stenosis. It is conventionally calculated as the ratio of the pressure distal (Pd) and proximal (Pa) to the stenosis (FFR= Pd/Pa). We hypothesize that the presence of a zero flow pressure (Pzf), requires a modification of this equation. Using a dynamic hydraulic bench model of the coronary circulation, which allows one to incorporate an adjustable Pzf, we studied the relation between pressure-derived FFR = Pdo/Pa, flow-derived true FFRQ = Qs/QN (= ratio of flow through a stenosed vessel to flow through a normal vessel), and the corrected pressure-derived FFRc = (Pd-Pzf)/(Pa-Pzf) under physiological aortic pressures (70 mmHg, 90 mmHg, and 110 mmHg). Imposed Pzf values varied between 0 mmHg and 30 mmHg. FFRc was in good agreement with FFRQ, whereas FFR consistently overestimated FFRQ. This overestimation increased when Pzf increased, or when Pa decreased, and could be as high as 56% (Pzf=30 mmHg and Pa =70 mmHg). According to our experimental study, calculating the corrected FFRC instead of FFR, if Pzf is known, provides a physiologically more accurate evaluation of the functional severity of a coronary artery stenosis.
Claessens
Tom E
TE
Institute of Biomedical Technology (IBITECH), Hydraulics Laboratory, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium. Tom.Claessens@UGent.be
Van Herck
Paul L
PL
Matthys
Koen S
KS
Segers
Patrick
P
Vrints
Christiaan J
CJ
Verdonck
Pascal R
PR
D001794:Blood Pressure; D003326:Coronary Circulation; D004867:Equipment Design; D006801:Humans; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D014655:Vascular Resistance