The influence of duplex scanning on early patency rates of in situ bypass to the tibial vessels

Duplex scanning was used in the follow up of 49 in situ infrapopliteal bypasses per formed for limb salvage using the valve incision method. In 19 cases (39%) the peroneal artery was the best available vessel for distal insertion; the anterior tibial and dorsalis pedis were used in 17 cases (35%) and the posterior tibial artery and tibioperoneal trunk in 13 cases (26%). In the early postoperative period three AV fistulas presented with painful skin lesions. These were located using duplex scanning and following ligation rapid resolution followed. Primary patency at one month was 87% and was increased to 96% by successful correction of four out of six failed bypasses. A total of 11 stenoses were found in five bypasses between three and 15 months postoperatively. In four of these patients the ankle/arm index decreased by at least 0.15 between examinations. A comparison was made between the spectral analysis on duplex scanning and the findings on arteriography and at operation. Peak systolic frequencies greater than 6 000 Hz were associated with 50% or greater reduction in vein bypass diameter. The majority were corrected using vein patch angioplasty. Primary cumulative patency at two years was maintained at 68% while correction of two out of seven bypass failures raised this to 80%. Duplex scanning allows precise definition of vein bypass pathology, facilitates operative correction and increases long-term limb salvage.