Intraoperative transit-time flow as a predictor of failure after infrainguinal revascularization with heparin-bonded expanded polytetrafluoroethylene graft.

Introduction The Heparin-bonded expanded polytetrafluoroethylene (He-ePTFE) conduit is an option for patients requiring infrainguinal revascularization (iIR), but the risk of failure may be unpredictable, especially in cases with poor run-off. Intraoperative transit-time flow (TTF) provides an automated and quantitative analysis of flow and may serve as an adjunct evaluation during surgical revascularization. The aim of this study was to assess TTF in patients undergoing iIR with He-PTFE at three referral hospitals and to establish a predictive flow threshold for graft occlusion. Methods A prospective registry initiated in 2020 enrolled patients undergoing infrainguinal revascularization (iIR) using He-PTFE for critical limb ischemia or severe claudication, and TTF measurement was analyzed. Preoperative assessments of anatomical and clinical characteristics were available for all patients. The HT353 Optima Meter (Transonic Systems Inc., Ithaca, NY, USA) was used in all procedures according to a standardized protocol. The institutional ethics committee approved the study. A predictive model using receiver operating characteristic curve (ROC) analysis was utilized to establish the threshold of flow, and variables were compared. Anatomical and clinical evaluation were reported according to Rutherford grade, Global Limb Anatomic System (GLASS) and Wound, Ischemia and foot Infection (WIfI) classification. The main outcome considered was the correlation between TTF and graft occlusion. Secondary outcomes included survival, other predictors of graft occlusion, freedom from major adverse cardiovascular events (MACE), and freedom from major amputation. Results Among 68 patients, 55.8% had Rutherford 5-6, 45.6% had GLASS 3 and 73.5% had WIfI 3-4. Distal anastomosis was at tibial level in 23.5% and mean diameter of conduit was 6.4mm. Basal and post-operative TTF was 27.8 ± 15.6ml/min and 109.0 ± 53.0mil/min, respectively. After a mean follow up of 18 ± 13 months, 7 (10.9%) patients presented graft occlusion and 5 (7.8%) required major amputation. TTF threshold = 80 ml/min revealed a sensitivity and specificity of 81.8% (95%CI 48,2 - 97,7) and 80.7% (95% CI 68,1 - 90,0) respectively and it was selected as cut-off for graft occlusion. Freedom from graft occlusion in patients with TTF >80ml/min vs TTF ≤80ml/min at 6, 12, 24 months was 95.7% (SE=0.030) vs 65.5% (SE= 0.115), 95.7% (SE =0.030) vs 58.9% (SE=0.120) and 90.9% (SE=0.054) vs 51.6% (SE=0.126), p= 0.0003. No statistical difference in primary patency, secondary patency and limb salvage was observed. At multivariate analysis, distal anastomosis at tibial vessel (OR 8.50) and TTF ≤80ml/min (OR 9.39) were independent predictors of graft occlusion. Conclusions These results suggest that TTF may serve as a valuable tool in the management of iIR. An TTF measurement of ≤80 ml/min should be regarded as a predictor of graft occlusion, prompting consideration of additional intraoperative maneuvers to enhance arterial flow. Caution should be exercised in patients requiring direct tibial artery revascularization, as it represents a predictor of failure independent of TTF levels. Larger cohorts of patients and longer follow-up periods are necessary to confirm these findings.