Postoperative surveillance of infrainguinal bypass

An effective graft-surveillance protocol needs to be applicable to all patients; practical in terms of time, effort, and cost; reliable; and able to detect, grade, and assess progression of lesions. The combination of pressure measurements and duplex color-flow imaging is the most effective technique for infrainguinal bypass surveillance. The accuracy of this protocol for the detection of graft stenosis is comparable to arteriography, and graft revision can be recommended and implemented based on noninvasive testing alone. Although similar anatomic and blood-flow data can be obtained by conventional duplex scanning, graft surveillance using color-flow imaging is preferred because both vascular anatomy and hemodynamics are evaluated simultaneously, a feature that improves diagnostic accuracy and reduces examination time. By contrast, resting ABI measurements alone are unable to identify reliably a failing graft; they are useful primarily for confirming technical adequacy and relief of ischemia. Data exist that confirm that long-term patency of infrainguinal bypasses is improved if hemodynamically significant stenoses are revised prior to graft thrombosis rather than revised or replaced after thrombosis. Both symptomatic and asymptomatic patients should undergo graft revision when noninvasive testing has confirmed the presence of a correctable lesion that reduces both limb pressure (change in ABI greater than 0.15) and graft blood-flow velocity (Vp less than 45 cm per second). Drops in pressure can occur in the absence of abnormalities in graft blood flow, but this condition does not indicate impending graft thrombosis. The identification of high-grade (greater than 75 per cent) stenosis by duplex scanning or color-flow imaging has been uniformly associated with a reduced ABI and increased risk of graft thrombosis. Less-severe lesions can be followed for disease progression as long as graft blood flow is adequate to sustain patency. In bypasses with low flow but no correctable abnormality, oral anticoagulation with warfarin sodium may decrease the incidence of graft thrombosis.