Effect of Stent-Graft Active Fixation and Oversizing on Aortic Neck Dilation After Endovascular Aneurysm Exclusion For Infrarenal Aortic Aneurysm.

INTRODUCTION: Aortic neck dilation post endovascular aneurysm repair (EVAR) has been implicated in the long-term development of endoleak and the subsequent re-intervention. Optimal endograft sizing is a vital aspect to successful repair. This study looked at percentage of graft oversizing as well as type of fixation on aortic neck dilation. METHODS: We retrospectively evaluated all EVARs completed at Loyola's University from 2006 to 2015 after IRB approval. Patients without follow-up scans within a year were excluded. We collected demographics, comorbidities, graft type, size, aortic neck diameter, maximum sac size diameters from the pre-operative and follow-up scans. We reviewed and collected data on 432 patients but analyzed 154. We measured the largest aortic diameter on axial images 1 cm above and 1 cm below the lowest renal artery. Change in supra and infrarenal aortic measurements were evaluated by calculating the mm difference from each scan compared to the pre-operative scan. Linear mixed effects models were used to estimate patients' mean differences over time. RESULTS: We compared three groups of neck fixation grafts. Those with active suprarenal fixation had a significant change in suprarenal aortic diameter at four-year follow-up (1.86 mm, CI:0.65-3.06), compared to those with active infrarenal (0.22 mm, CI: -0.67 to -1.11) or passive suprarenal fixation (1.52 mm, CI: -0.11 to -3.15) (Fig. 1). Those with active suprarenal fixation were the only ones to have significant increase in suprarenal aortic diameter (P = 0.0026). Degree of oversizing was also divided into three groups. Oversizing by <10% had less impact on the suprarenal aorta than >15% oversizing at 4 years (0.41 mm, CI: -0.31 to -1.14 vs. 3.26 mm, CI: 1.63-4.88, P < 0.001) (Fig. 2). Oversizing had a more pronounced effect on the infrarenal aorta: 3.01 mm, CI: 2.18-3.83; 5.95 mm, CI: 3.26-8.64; and 5.05 mm, CI: 3.41-6.69 for <10%, 10-15%, and >15% oversizing at four years, respectively. CONCLUSION: Stent-grafts with active fixation below the renal arteries as well as oversizing by <10% seem to have the least effect on aortic neck dilation over time. These factors should be considered when performing EVARs, as aortic neck dilation could lead to endoleak and need for further intervention. Further research defining the optimal stent-graft type, self-expanding versus balloon expandable, type of fixation and degree of oversizing.

Evaluating effectiveness of antibiotic polymethylmethacrylate beads in achieving wound sterilization and graft preservation in patients with early and late vascular graft infections.

OBJECTIVE: The objective of the study was to evaluate the effectiveness of antibiotic-based polymethylmethacrylate (ab-PMMA) beads in achieving wound sterilization and graft preservation in patients with vascular graft infections. METHODS: We reviewed 31 patients treated for 37 graft infections over the past 5 years using ab-PMMA beads in a single institution. All patients were started on broad-spectrum antibiotics and later switched to targeted therapy based on intraoperative cultures for at least 6 weeks. All patients underwent multiple planned wound explorations, debridements and washouts. Cultures were obtained each time. Decision to do formal closure depended on culture results and wound appearance. All wounds were closed with a muscle flap. The endpoints included wound sterilization, limb salvage, recurrence of infection, and graft preservation. RESULTS: A total of 19 different organisms were cultured, and 48.6% of cases were polymicrobial, thereby accounting for a total of 60 isolates. The majority (n = 27) received a mix of tobramycin/vancomycin PMMA beads; vancomycin beads (n = 5); tobramycin beads (n = 1); and gentamicin/vancomycin beads (n = 4). Wound sterilization based on cultures was achieved in 32 of 34 wounds (94.1%). Of the cases, 5 underwent early graft removal, 3 with immediate reconstruction, and 1 case underwent a major amputation (2.7 %). Graft preservation was attempted in 32 cases (86.5%). No death occurred within 30 days. Limb salvage was achieved in 28 of the 32 preserved graft cases (87.5%) at a mean follow-up of 26 months (6 to 51 months). The long-term limb salvage rate for the cohort was 86.5%. Of the patients, 4 presented with recurrent graft infection and occlusion, causing acute limb ischemia and resulting in major amputation. The reinfection rate was 12.5% in the graft-preservation group and 11.4% in both the graft-preserved and the in situ replacement groups. CONCLUSION: Sterilization of graft infection can be achieved with ab-PMMA beads followed by closure with muscle flap, resulting in an acceptable limb-salvage rate despite virulent or polymicrobial graft infection.