Infrainguinal vein bypass graft surveillance: How to do it, when to intervene, and is it cost-effective?

It has been demonstrated that infrainguinal bypass graft patency can be effectively maintained by a noninvasive vascular laboratory program capable of identifying vein graft stenosis followed by elective correction of lesions that meet threshold criteria. Autologous vein bypass grafts constructed by either the reversed, nonreversed, or in situ grafting technique are prone to developing intrinsic lesions after implantation into the arterial circulation. Despite careful operative technique and assessment for technical adequacy, a stenosis can reside within the arterial bypass or develop as a result of vein graft arterialization. Clinical examination that includes patient questioning for symptoms of limb ischemia, pulse evaluation, and measurement of ankle systolic pressure can identify only high-grade graft stenosis or occlusion. Duplex ultrasonography is a more accurate diagnostic method for detection of graft stenosis. Prospective observational studies that used duplex scanning have confirmed that fibrous strictures develop in 20% to 30% of infrainguinal vein bypasses during the first postoperative year. These stenotic lesions are typically the result of myointimal hyperplasia, and, if not corrected, are associated with a three-fold increase in graft occlusion, accounting for up to 80% of graft failures within 3 to 5 years of the primary grafting procedure. Lesions with duplex-derived velocity spectra of a high-grade stenosis (peak systolic velocity [PSV] 300cm/sec, end diastolic velocity 20cm/sec, velocity ratio across the stenosis 3.5) or greater than 70% diameter reduction by arteriography are associated with graft failure if not corrected. Multiple investigators have observed an approximate 25% incidence of graft thrombosis in stenotic bypasses if a policy of no intervention was followed. Idu and associates reported that all infrainguinal vein grafts with a 70% diameter reduction stenosis eventually occluded compared with 10% of repaired grafts with similar lesions. Surveillance programs based on duplex scanning have increased assisted-primary patency rates to 82% to 93% at 5 years compared with 60% to 70% patency for bypasses followed clinically, and 30% to 50% patency rates after secondary procedures to salvage thrombosed vein grafts. The enhanced patency associated with duplex surveillance has been confirmed in a randomized, prospective clinical trial conducted in Malmo, Sweden. A 25% improvement in infrainguinal vein bypass patency at 3 years (78% versus 53%) occurred with duplex surveillance, but no significant benefit was documented in PTFE or PTFE-vein composite graft patency. These observations are important measures of efficacy because “redo” bypass procedures are difficult or might not be possible; ie, if no suitable outflow artery or other vein conduit is available. Of note, a recent report from Finland did not demonstrate benefit from duplex surveillance after infrainguinal vein bypass, but adherence to the duplex scan protocol and graft failure after revision were major problems identified by the authors, limiting the effectiveness of the surveillance program.