Comparison Between Autogenous Saphenous Vein and Heparin-Bonded Expanded Polytetrafluoroethylene for Below-the-Knee Popliteal and Tibial Bypasses in Patients With Critical Limb Ischemia

Patient population, indications for surgery, and surgical strategy

From January 2002 to December 2022, 625 consecutive femoropopliteal bypasses were performed at our institution. Data on these interventions were collected in a dedicated multitasking database; data collection was retrospective until 2008 and was prospective thereafter. 

A retrospective analysis of this database was performed, and 337 BTK bypass procedures performed for CLI were found. Among these, 145 used ASV and 192 utilized HePTFE (Propaten vascular graft [Gore]). This graft has been available for use in Italy since the end of 2001. Thirty-nine above-the-knee (ATK) HePTFE bypasses in patients with CLI were performed in the same period, which were excluded from the analysis. Informed consent for the treatment of personal data was obtained from each patient upon hospital admission. The Institutional Review Board did not require approval for the retrospective analysis of the data. The interventions conducted prior to 2019 had been previously documented in publications from the multicenter Italian Registry on the HePTFE graft, which encompasses our center’s involvement in 234 procedures.^7,8,11,12 Results from these interventions were also part of a single-center publication.¹⁴ The current study updates these findings by incorporating data from procedures performed after 2019.

The surgery was recommended for individuals experiencing CLI, characterized by ischemic rest pain and an ankle-brachial index (ABI) below 0.4 or tissue loss (ulceration, gangrene).¹⁵ This recommendation applied to patients with a low-to-moderate surgical risk (with an estimated perioperative mortality < 5% and a 2-year estimated survival rate exceeding 50%). Additionally, surgery was advised in the presence of challenging infrainguinal lesions, such as long occlusions of the superficial femoral artery (SFA), involvement of the popliteal artery and popliteal trifurcation, severe and widespread calcifications of the SFA, and less complex lesions following an unsuccessful prior endovascular treatment.

All patients underwent both duplex scanning of the lower extremities and computed tomography angiography (CTA) scans from the abdominal aorta to the tibial and foot vessels. The duplex examination included an assessment of the ipsilateral great saphenous vein (GSV), which was deemed optimal if it had a diameter greater than 4 mm, was devoid of varicosities, and showed no signs of previous thromboses. The decision to employ a prosthetic graft was not solely based on the absence of a suitable vein; in selected cases, patients with a good-quality ASV (as determined by the surgeon’s clinical and anatomical considerations, habits, and experience) were also considered. The contralateral saphenous vein or alternative veins were not considered as potential sources for venous materials.

The intervention was conducted under general anesthesia, with all patients receiving intravenous systemic heparinization at a dose of 30 IU/kg, followed by additional doses based on activated clotting time (ACT) values. When utilizing the GSV, both in situ and reversed techniques were employed at the surgeon’s discretion, following the standard technique of our institution. In the HePTFE group, adjunctive procedures to enhance inflow were selectively performed, and a liberal approach to techniques for improving runoff was adopted at the outflow level. For the ASV group, the use of proximal and distal adjunctive procedures was selective, considering the status of the femoral bifurcation and the presence of significant concurrent lesions in the popliteal or tibial arteries. Patients who had a distal anastomosis at the tibioperoneal trunk were included among those with a BTK popliteal and not a tibial bypass. Completion angiography or intraoperative duplex ultrasound was routinely conducted. Patients with extensive ulcers or dry gangrene of the foot underwent concomitant toe and/or forefoot amputation. In both groups, patients were discharged with prescribed double antiplatelet therapy for a minimum of 3 to 6 months, followed by a single antiplatelet therapy indefinitely. Warfarin therapy was continued after discharge for patients who were on it prior to the lower extremity intervention or those deemed at increased risk of failure (eg, redo surgery, concurrent severe disease of the tibial vessels), sometimes in combination with single antiplatelet therapy. In selected cases, low-dose rivaroxaban plus aspirin was prescribed, particularly following the publication of the Voyager trial.¹⁶

Follow-up program

Follow-up assessments were conducted at 1, 3, and 12 months with subsequent evaluations every 6 to 9 months. During follow-up examinations, the clinical status was evaluated and duplex ultrasound performed to assess graft patency. The examination also checked for disease progression at the inflow and outflow levels, the presence of flow-limiting stenosis at anastomoses and along the graft course, and saphenous collaterals causing a reduction in flow velocity within the bypass. Graft occlusion was defined when blood flow was not detectable, while significant stenosis was characterized by an increase in trans-stenotic peak systolic velocity (PSV) exceeding 300 cm/sec or a PSV ratio value exceeding 3.5. Reintervention was recommended in the presence of significant stenosis, whether symptomatic or asymptomatic, or in cases of occlusion leading to severe claudication, CLI, or acute limb ischemia. Additional data concerning long-term survival, major cardiovascular events, and subsequent hospitalizations were obtained from the Regional Health Care database.

Outcomes and statistics

Perioperative outcomes were scrutinized, encompassing mortality, graft thrombosis, major amputations (ATK or BTK), and severe local and systemic complications. The latter were defined as complications necessitating surgical, medical, or endovascular interventions, and included instances involving prolonged convalescence and lasting disability.¹⁷ Follow-up outcomes were primary and secondary patency, freedom from major amputation, amputation-free survival (AFS), and overall survival. The analysis of follow-up results concluded in September 2023.

To compare the 2 groups (HePTFE and ASV), perioperative results were analyzed using χ2 tests and Fisher’s exact tests when necessary. Follow-up data were assessed using Kaplan-Meier curves and compared with the log-rank test. The follow-up index (FUI) for late survival was determined in the study group, which was defined as the ratio between the investigated follow-up period and the theoretically possible follow-up period up to September 2023. Univariate analysis, employing Kaplan-Meier survival estimates and log-rank tests for each covariate, was performed to identify potential significant predictors of AFS. Covariates showing a P value less than or equal to 0.2 in univariate analysis were included in a forward Cox regression analysis for primary patency, with measurement of hazard ratio (HR) and confidence intervals (CI; significance criteria: 0.25 for entry, 0.05 for removal). Statistical analysis was carried out using dedicated Windows software (Statistical Package for the Social Sciences [SPSS] 26), with statistical significance defined as a P value of less than 0.05.