Fig. 1

Pre-stenotic \(P_0(t)\) (red lines) and post-stenotic \(P_1(t)\) (green lines) pressure waveforms over 25 cycles. The FFR value 0.83 is taken as the minimum of the ratio between the functions \(\overline{P}_0(t)\) and \(\overline{P}_1(t)\) (smooth curves) calculated from those waveforms. The pressure waveforms were provided by the Hospital Infanta Cristina in Badajoz (Spain)