Undetected aorto-iliac insufficiency: a reason for early failure of saphenous vein bypass grafts for obstruction of the superficial femoral artery.

A series of 29 femoropopliteal bypass operations is described. The patients were selected carefully to exclude those with clinical and aortographic evidence of aorto-iliac disease. A pulsatility index was calculated from the velocity waveforms recorded over the common femoral and popliteal arteries. The pulsatility index is the ratio of the amplitude of the waveform to its mean height over one cardiac cycle. There was a highly significant difference in the result of the operation between patients with a pulsatility index of 4 or more in the common femoral artery and patients with a pulsatility index of less than 4. We concluded that calculation of this pulsatility index provides useful additional evidence when selecting patients suitable for a femoropopliteal bypass.