Clearly duplex surveillance of infrainguinal bypass grafts is beneficial, but how long does the surveillance program need to continue? Most reviews have shown a definite benefit up to 2 years based on the fact that 70–80% of all graft abnormalities develop and require revision during this time period. Erickson and co-workers recommend that surveillance continues indefinitely for autogenous bypass grafts [46]. They reported that 18% of the initial interventions for a duplex-detected lesion occurred after the initial 24-month period. Sixty-three percent of these defects occurred at an anastomosis. Although the incidence of vein graft stenosis developing decreases over time, atherosclerotic changes continue in native arteries. Another important finding to look for in older vein grafts is aneurysmal degeneration of the vein. Vein dilation is usually focal and can be associated with mural thrombus, which may warrant segmental graft revision. We support the concept of lifelong vein graft surveillance, which also gives the vascular surgeon the opportunity to monitor development of atherosclerosis in other vascular beds.

Duplex ultrasonography is the method of choice for the surveillance of infrainguinal bypass grafts. Noninvasive vascular laboratories should continuously correlate its interpretations with arteriographic findings and clinical outcomes. Any focal PSV > 300 cm/s or a PSV ratio > 3.5 between two adjacent segments is generally accepted as a strong indicator for a focal stenosis that may threaten graft patency. Low PSVs throughout the graft (<45 cm/s), as well as lack of diastolic forward flow as evidenced by loss of biphasic Doppler signals throughout the graft, may also indicate inflow or outflow problems and warrant further investigation. Arteriography and appropriate endovascular or open surgical revision of failing grafts should be judiciously implemented by the vascular surgeon to improve long-term patency and limb salvage rates.