The role of colour flow duplex screening in infra-inguinal vein grafts.

To assess the indications for routine colour flow duplex surveillance, 43 infra-inguinal autogenous vein grafts were prospectively entered into a surveillance protocol. Screening consisted of measurements of ankle brachial indices (ABIs) and colour flow duplex imaging of the entire graft length. Twelve significant stenoses have been detected in 10 grafts (23%) using duplex, all within 6 months of surgery. All grafts at risk had arteriography confirming the duplex findings, but detecting one additional stenosis. Two grafts at risk were not detected by duplex scanning (sensitivity 83%). All grafts at risk (12) had a serial fall in resting ABI of more than 0.1. Most of the detected graft stenoses could be corrected surgically, improving the 1 year primary cumulative patency rate of 54% to a secondary patency rate of 88%. This study suggests that resting ABI measurements are a very sensitive (sensitivity: 100%) and simple primary screening procedure, provided that all grafts with ABI changes of more than 0.1 are further evaluated. The interval specificities of ABI measurements were 77% at 3, 71% at 6, 67% at 12 and 78% at 18 months (mean 73%). About 60% of ABI-screened grafts needed further evaluation because of ABI changes of greater than 0.1, incompressibility of arteries (ABI greater than 1.3) or extension of the graft to the ankle or pedal arteries. Colour flow duplex scanning was very useful in excluding or identifying and localising graft problems and deciding on further invasive diagnostic and therapeutic procedures. Ankle brachial index measurements as the primary examination for selecting patients for colour flow duplex scanning seems to be a safe screening procedure.