Use of Heparin-Bonded Expanded Polytetrafluoroethylene Grafts for Renal Artery Reconstruction

Biaxial stretching of polytetrafluoroethylene in industrial scale to fabricate medical ePTFE membrane with node-fibril microstructure

Expanded polytetrafluoroethylene (ePTFE) is promising in biomedical fields such as covered stents and plastic surgery owing to its excellent biocompatibility and mechanical properties. However, ePTFE material prepared by the traditional biaxial stretching process is with thicker middle and thinner sides due to the bowing effect, which poses a major problem in industrial-scale fabrication. To solve this problem, we design an olive-shaped winding roller to provide the middle part of the ePTFE tape with a greater longitudinal stretching amplitude than the two sides, so as to make up for the excessive longitudinal retraction tendency of the middle part when it is transversely stretched. The as-fabricated ePTFE membrane has, as designed, uniform thickness and node-fibril microstructure. In addition, we examine the effects of mass ratio of lubricant to PTFE powder, biaxial stretching ratio and sintering temperature on the performance of the resultant ePTFE membranes. Particularly, the relation between the internal microstructure of the ePTFE membrane and its mechanical properties is revealed. Besides stable mechanical properties, the sintered ePTFE membrane exhibits satisfactory biological properties. We make a series of biological assessments including in vitro hemolysis, coagulation, bacterial reverse mutation and in vivo thrombosis, intracutaneous reactivity test, pyrogen test and subchronic systemic toxicity test; all of the results meet the relevant international standards. The muscle implantation of the sintered ePTFE membrane into rabbits indicates acceptable inflammatory reactions of our sintered ePTFE membrane fabricated on industrial scale. Such a medical-grade raw material with the unique physical form and condensed-state microstructure is expected to afford an inert biomaterial potentially for stent-graft membrane.

Effects of Suprarenal Aortic Cross-Clamping and Adjunctive Renal Reconstruction on Outcomes of Open Abdominal Aortic Aneurysm Repair

PURPOSE

To analyze our contemporary experience in open abdominal aortic aneurysm (AAA) repair. We focused on the effects of suprarenal (SR) aortic cross-clamping and adjunctive renal reconstruction (RR) on postoperative outcomes.

METHODS

We retrospectively reviewed our institutional data of 141 consecutive patients who received elective open AAA repair between January 2014 and December 2020.

RESULTS

Seventy-five procedures were performed with SR aortic cross-clamping, 20 of which required an adjunctive RR. Patients in the SR group had a higher incidence of postoperative acute kidney injury (AKI) (18.7% vs. 7.6%, P = 0.045). There were no significant between-group differences in other major complications. The 30-day mortality rate in the infrarenal (IR) and SR groups was 0% and 1.3%, respectively. After a median follow-up of 33 months, the rates of chronic renal decline in the IR (18.2%) and SR (21.3%) groups were similar. All reconstructed renal arteries were patent without reintervention. The 5-year overall survival rate in the IR and SR groups was 88.8% and 83.2%, respectively.

CONCLUSIONS

SR aortic cross-clamping was associated with postoperative AKI but neither SR aortic cross-clamping nor RR affected the long-term renal function or mortality. Open repair remains an essential option for patients with AAA, especially those with complex anatomy.