A dumbbell rescue stent graft facilitates clamp-free repair of aortic injury in a porcine model

Abstract

Objective: Noncompressible torso hemorrhage is a high-mortality injury. We previously reported improved outcomes with a retrievable rescue stent graft to temporize aortic hemorrhage in a porcine model while maintaining distal perfusion. A limitation was that the original cylindrical stent graft design prohibited simultaneous vascular repair, given the concern for suture ensnarement of the temporary stent. We hypothesized that a modified, dumbbell-shaped design would preserve distal perfusion and also offer a bloodless plane in the midsection, facilitating repair with the stent graft in place and improve the postrepair hemodynamics.

Methods: In an Institutional Animal Care and Use Committee-approved terminal porcine model, a custom retrievable dumbbell-shaped rescue stent graft (dRS) was fashioned from laser-cut nitinol and polytetrafluoroethylene covering and compared with aortic cross-clamping. Under anesthesia, the descending thoracic aorta was injured and then repaired with cross-clamping (n = 6) or dRS (n = 6). Angiography was performed in both groups. Operations were divided into phases: (1) baseline, (2) thoracic injury with either cross-clamp or dRS deployed, and (3) recovery, after which the clamp or dRS were removed. Target blood loss was 22% to simulate class II or III hemorrhagic shock. Shed blood was recovered with a Cell Saver and reinfused for resuscitation. Renal artery flow rates were recorded at baseline and during the repair phase and reported as a percentage of cardiac output. Phenylephrine pressor requirements were recorded.

Results: In contrast with cross-clamped animals, dRS animals demonstrated both operative hemostasis and preserved flow beyond the dRS angiographically. Recovery phase mean arterial pressure, cardiac output, and right ventricular end-diastolic volume were significantly higher in dRS animals (P = .033, P = .015, and P = .012, respectively). Whereas distal femoral blood pressures were absent during cross-clamping, among the dRS animals, the carotid and femoral MAPs were not significantly different during the injury phase (P = .504). Cross-clamped animals demonstrated nearly absent renal artery flow, in contrast with dRS animals, which exhibited preserved perfusion (P<.0001). Femoral oxygen levels (partial pressure of oxygen) among a subset of animals further confirmed greater distal oxygenation during dRS deployment compared with cross-clamping (P = .006). After aortic repair and clamp or stent removal, cross-clamped animals demonstrated more significant hypotension, as demonstrated by increased pressor requirements over stented animals (P = .035).

Conclusions: Compared with aortic cross-clamping, the dRS model demonstrated superior distal perfusion, while also facilitating simultaneous hemorrhage control and aortic repair. This study demonstrates a promising alternative to aortic cross-clamping to decrease distal ischemia and avoid the unfavorable hemodynamics that accompany clamp reperfusion. Future studies will assess differences in ischemic injury and physiological outcomes.

Clinical relevance: Noncompressible aortic hemorrhage remains a high-mortality injury, and current damage control options are limited by ischemic complications. We have previously reported a retrievable stent graft to allow rapid hemorrhage control, preserved distal perfusion, and removal at the primary repair. The prior cylindrical stent graft was limited by the inability to suture the aorta over the stent graft owing to risk of ensnarement. This large animal study explored a dumbbell retrievable stent with a bloodless plane to allow suture placement with the stent in place. This approach improved distal perfusion and hemodynamics over clamp repair and heralds the potential for aortic repair while avoiding complications.

Keywords: Aortic cross-clamp; Aortic trauma; Endovascular; Temporary stent; Torso hemorrhage.

Fig 1

The retrievable stent provides deployment by sheath withdrawal for damage control of hemorrhage (A, B, and C) and retrieval by sheath advancement over a permanently attached delivery wire to collapse the stent (D). Nevertheless, the cylindrical design (E) is unfavorable for direct suture repair, because the suture might ensnare the stent. Alternately, a dumbbell-shaped stent (F) provides an essentially bloodless compartment for suture placement, all while preserving distal perfusion.

Fig 2

Aortic control from a more anatomically favorable location. The dual chamber Rescue stent graft inserts from an infrarenal (or more favorable femoral) access remote from the actual operative site, which may be obscured by bleeding. The stent graft creates a bloodless operative zone, while at the same time ensuring distal perfusion.

Fig 3

Retrievable rescue stent. A computer modeled stent (A) is laser cut from nitinol to create a scaffold (B), followed by shapesetting onto a dumbbell mandrel (C). The shapeset scaffold (D) is covered with encapsulated polytetrafluoroethylene (PTFE) (E). Later, a nosecone and a permanently attached delivery wire for the final stent graft before compression into a 12F sheath (F).

Fig 4

Study design consisting of (A) terminal porcine model of thoracic aortic injury with intentional blood loss, then use of either (B) aortic cross-clamp or (C) dumbbell rescue stent graft deployment, followed by (D) a permanent aortic repair with a sutured vascular patch while the clamp or stent is in place.

Fig 5

Angiogram after cross-clamping (A) reveals absent distal perfusion. Conversely, a dumbbell rescue stent placed in the thoracic aorta preserves perfusion through the center lumen of the stent (B, aortic wall outlined) and distally to the viscera (C). Simultaneously, the stent graft created an isolated outer chamber (D), which forms a bloodless operative field, aside from small intercostal backbleeding. SMA, superior mesenteric artery.

Fig 6

Sutured patch repair of the thoracic aorta with dumbbell rescue stent in place and providing proximal and distal hemorrhage control. The stent center lumen is outlined by the thin dashed yellow line.