Duplex Ultrasound for Diagnosis of Failing Stents Placed for Lower Extremity Arterial Occlusive Disease.

Background: Noninvasive diagnostic testing may be beneficial to identify stenotic (failing) stents placed for occlusive lower extremity peripheral arterial disease (LEPAD), especially if subsequent intervention proves useful in maintaining prolonged stent patency. We previously documented the benefit of surveillance duplex ultrasound (DU) for peripheral covered stents (stent grafts). The purpose of this study was to evaluate whether DU can reliably diagnose failing bare metal stents placed in iliac, femoral, and popliteal arteries for LEPAD.

Methods: Between January 1, 2013, and December 31, 2016, 172 stents were placed for LEPAD in 119 arterial segments (1.4 stents/stenotic artery) in 110 patients who underwent one or more DU surveillance study documenting stent patency. Poststent DU surveillance was performed in our Intersocietal Accreditation Commission accredited noninvasive vascular lab at 1 week and then every 6 months. DU measured peak systolic velocities (PSVs) and ratio of adjacent PSVs (Vr) every 2.0 cm within the stent(s) and adjacent arteries. We retrospectively classified the following factors as "abnormal DU findings": focal PSVs >300 cm/s, uniform PSVs <45 cm/s, and Vr > 3.0.

Results: During average follow-up of 22 months (range, 1 week-48 months), all three of these DU criteria were "normal" in 62 (52%) of the 119 stented segments. Of the other 57 (48%) stented arterial segments that had one or more abnormal DU findings, 40 underwent prophylactic intervention, 12 patients did not undergo intervention and subsequently occluded (5 patient refusal, 4 surgeon-decision, 3 shortened surveillance interval), and 5 remained patent after mean follow-up of 7.2 months. Of the 12 arterial segments that occluded, 6 patients chose not to have further intervention, 4 failed additional endovascular intervention and required an arterial bypass, and 2 required amputation. Therefore, of the 17 stented arterial segments with one or more abnormal DU findings that did not undergo intervention, 12 (70%) went on to occlude versus 2 of 62 (3%) with normal DU findings demonstrating an odds ratio of 72.0 (95% CI 12.5-415.6, P < 0.0001). Of these 12 stented arterial segments with abnormal DU findings that occluded, 7 had uniform low PSVs alone, 3 had both abnormal PSV and Vr's, and 2 had abnormal Vr's alone.

Conclusions: DU surveillance can predict LEPAD stent occlusion. While PSV >300 cm/sec alone is not a statistically significant predictor of stent failure, Vr > 3.0, and most importantly, uniform PSVs <45 cm/s throughout the stent were statistically reliable markers for predicting stent thrombosis, while the absence of any of these abnormalities strongly predicted stent patency.