In vivo evaluation of a new hybrid graft using retrograde visceral perfusion for thoracoabdominal aortic repair in an animal model

Abstract

Objectives: The SPIDER technique for hybrid thoracoabdominal aortic aneurysm repair can avoid thoracotomy and extracorporeal circulation. To improve technical feasibility and safety, the new Thoracoflo graft, consisting of a proximal stent graft connected to a 7-branched abdominal prosthesis, was evaluated in a pig model for technical feasibility testing, before implantation in humans.

Methods: Retroperitoneal exposure of the infradiaphragmatic aorta, including visceral and renal arteries, was performed in 7 pigs (75-85 kg). One iliac branch was temporarily attached to the distal aorta to maintain retrograde visceral and antegrade iliac perfusion after deployment of the thoracic stent graft segment (SPIDER technique). The proximal stent-grafted segment was deployed in the thoracic aorta via direct aortic puncture over the wire without fluoroscopy. The graft was deaired before flow via the iliac side branch to the visceral and iliac arteries was established. Visceral, renal, and lumbar arteries were subsequently sutured to the corresponding side branches of the graft. Technical feasibility, operating and clamping time, blood flow, and tissue perfusion in the related organs were evaluated before implantation and after 3 and 6 hours using transit-time flow measurement and fluorescent microspheres. Final angiography or postprocedural computed tomography angiography were performed.

Results: Over-the-wire graft deployment was successful in 6 animals without hemodynamic alteration (P = n.s.). In 1 pig, the proximal stent graft section migrated as the guidewire was not removed, as recommended, before release of the proximal fixation wire. Angiography and computed tomography scan confirmed successful graft implantation and transit-time flow measurement confirmed good visceral and iliac blood flow. Fluorescent microspheres confirmed good spinal cord perfusion.

Conclusions: Over-the-wire implantation of the Thoracoflo graft using the SPIDER technique is feasible in a pig model. No fluoroscopy was required. For safe implantation, it is mandatory to follow the single steps of implantation.

Keywords: CO, cardiac output; CT, celiac trunk; ECC, extracorporeal circulation; FM, fluorescent microspheres; LRA, left renal artery; MBP, mean arterial blood pressure; OAR, open aortic repair; OP, operative; RRA, right renal artery; SMA, superior mesenteric artery; SPIDER technique; SVR, systemic vascular resistance; TAAA; TAAA, thoracoabdominal aortic aneurysm; TTFM, transit-time flow measurement; Thoracoflo; hybrid aortic repair; thoracoabdominal aortic repair.

Thoracoflo graft prototype with proximal ring-shaped stent graft.

Figure 1

A, Thoracoflo graft prototype with proximal ring–shaped stent graft connected to 7-branched gelatin-sealed Dacron graft for reattachment of visceral and renal arteries, iliac arteries, and reimplantation of lumbar arteries, in between collar for graft fixation. The handle (1) with release clip (2) for the fixation wire of the proximal stent graft component on the introducer tip (3), equipped with a side hole for introduction of the guidewire, is outsided through the 10-mm access branch. The stent graft is loaded in a splitable 30-F peel-away sheath (4) and fixed with a splitter (5). B, Deployed Thoracoflo graft prototype shown from the dorsal side: thoracic stent graft (24 mm diameter, 150 mm length): collar (1) at connection to Y-shaped arm for biliary reattachment and 4 prosthetic arms for reimplantation of celiac trunk (2); superior mesenteric artery (3); and both renal arteries (4, 5). The access branch (6) was used as loop graft for reimplantation of lumbar arteries.

Figure 2

Technical steps of Thoracoflo graft implantation. A, Ligation of contralateral iliac branch and visceral side and temporary connection of the iliac side branch to distal aorta or iliac artery in end-to-side fashion. Clamping of the iliac branch. B, Puncturing of the aorta close to the coeliac trunk ostium and guidewire introduction. C, Over-the-wire introduction of the stent-grafted section of the Thoracoflo graft until the collar is just outside the puncture hole. Guidewire is outsided through a side hole of the tip. D, Retraction of the guide-wire. E, Retraction of the peel-way sheath. F, Release of wire for proximal fixation wire of the stent graft. G, Opening of splitter and removement of the handle through the access branch. H, Establishment of retrograde visceral perfusion by release of clamp on iliac branch. I, Subsequent reattachment of visceral and renal arteries and reattachment of lumbar arteries.