Enhanced Efficacy of Duplex Ultrasound Surveillance after Infrainguinal Vein Bypass by Identification of Characteristics Predictive for Graft Stenosis Development

Background: Controversy exists regarding the efficacy of routine duplex ultrasound surveillance following infrainguinal vein bypass. In this study, bypass graft characteristics predictive for graft stenosis development and need for secondary intervention were identified with a goal to enhance the clinical benefit of duplex graft surveillance, and refine protocols for testing frequency.
Methods: Retrospective analysis of a contemporary, consecutive series of 348 clinically successful infrainguinal vein bypasses performed in 324 patients for critical (n=281; 81%) or non-critical (n=67; 19%) limb ischemia, and enrolled in a surveillance program to identify and repair duplex-detected graft stenosis. Variables correlated with graft stenosis and bypass repair included: procedure indication, conduit type (arm vs. saphenous vein; reversed vs. non-reversed orientation), prior bypass graft failure, postoperative ankle-brachial index (ABI) > or < 0.85, and interpretation of the 1st duplex surveillance study as “normal” or “abnormal” based on peak systolic velocity (PSV) and velocity ratio (Vr) criteria of stenosis severity.
Results: Overall, 121 (35%) of 348 infrainguinal bypasses had 165 secondary interventions (endovascular: 93, open repair: 72) based on duplex testing; resulting in 3-yr life-table primary (61%), assisted-primary (84%), and secondary (86%) patency rates. Symptoms of limb ischemia were present in 40% of patients prior to graft revision. Characteristics predictive of graft stenosis requiring intervention (PSV>300 cm/s, Vr>3.5) were: “abnormal” 1st postoperative duplex testing indicating moderate (PSV: 180-300 cm/s, Vr: 2-3.5) stenosis (p<0.001), use of arm vein conduit (p<0.02), and redo bypass graft (p<0.02). Procedure indication, postoperative ABI level, statin drug therapy, and vein conduit orientation were not predictive of graft revision. The natural history of 140 (40%) bypasses with duplex abnormalities on initial testing differed from bypasses with “normal” 1st scans evidenced by a more frequent (51% vs. 24%, p<0.02) and earlier (mean time to revision: 6.4 mo. vs.10 mo.) subsequent revision rate for severe stenosis, a lower 3-yr assisted-primary patency rate (76% vs. 90%; p<0.05), and requirement for more complicated reparative procedures. In 50 (14%) limbs, the bypass graft failed - 60% of grafts revised one or multiple times; and 20 (6%) limbs required amputation.
Conclusions: The efficacy of duplex surveillance after infrainguinal vein bypass could be enhanced by modifying testing protocols, e.g. more frequent and rigorous surveillance for “higher risk” bypasses, based on the initial duplex surveillance scan results and other graft characteristics (arm vein conduit, redo bypass) predictive of stenosis development. Vein bypasses with a duplex-detected abnormality on early surveillance testing required earlier, more frequent, and complicated reparative procedures; and exhibited a higher failure rate.