Femoral flow redirection technique to limit visceral artery ischemia during fenestrated endovascular aortic repair

Abstract

Fenestrated endovascular aortic repair is an established treatment for complex juxtarenal and pararenal aneurysms but remains associated with postoperative renal insufficiency, partly due to reduced visceral perfusion during target vessel cannulation. We describe a femoral flow redirection technique that maintains continuous visceral perfusion during fenestrated endovascular aortic repair using a femoral sheath that passively redistributes flow to visceral sheaths. Femoral flow redirection can be successfully implemented without complications or clinically significant renal dysfunction and may serve as a simple adjunct to reduce ischemic insult during complex repair.

Fenestrated endovascular aortic repair (FEVAR) is a well-established treatment for complex juxtarenal and pararenal abdominal aortic aneurysms (AAAs), offering reduced perioperative morbidity compared with open surgical repair.^1,2 Despite these advantages, FEVAR remains associated with significant early complications, with major morbidity rates exceeding 20%.^1,3 Postoperative renal insufficiency is among the most common adverse outcomes and long-term mortality, with clinically significant renal dysfunction reported in up to 26% of patients.4, 5, 6

Renal dysfunction after FEVAR is multifactorial. Although contrast exposure has traditionally been implicated, growing evidence suggests that transient ischemia during target vessel cannulation plays a substantial role.^5,7 Placement of large sheaths and catheters for visceral vessel access can partially obstruct arterial inflow, resulting in inadequate perfusion during prolonged procedural stages, independent of contrast nephropathy.8, 9, 10, 11

Strategies to preserve visceral perfusion during complex endovascular repair remain limited. We describe a novel femoral flow redirection (FRED) technique designed to maintain continuous visceral vessel perfusion during FEVAR by redirecting femoral arterial inflow through catheter sheaths positioned in target arteries.

Presentation of the femoral flow redirection technique

The FRED technique is intended for patients with complex juxtarenal AAAs undergoing elective FEVAR. It is particularly useful in complex cases involving multiple renal and visceral target vessels, anticipated prolonged cannulation times, challenging anatomy, or patients at increased risk for ischemic renal injury. The technique has been applied in all visceral vessels. Because cannulation is performed through a large-bore femoral sheath, appropriate iliofemoral anatomy is essential. Sheath size may vary depending on patient anatomy, aneurysm characteristics, and the graft system being used. Although larger sheaths (eg, 22F) may restrict native arterial flow and increase the risk of lower extremity, pelvic, spinal cord, or visceral ischemia, operators may elect to use smaller 14F or 16F sheaths when feasible to maintain greater distal perfusion. The technique should be limited to patients who would otherwise tolerate the femoral access requirements of standard FEVAR and avoided in those with severe iliac stenosis, heavy calcification, or small-caliber access vessels where the risk of ischemic or access-related complications may outweigh potential benefits.

Bilateral common femoral artery access is obtained under ultrasound guidance using a preclose technique. On the side contralateral to the main body endograft delivery, the femoral artery is sequentially dilated, and a 22F Check-Flo sheath (Cook Medical) is inserted. The Check-Flo sheath is a flexible introducer with a hemostatic valve and is modified by puncturing its membrane in four quadrants to allow passage of smaller sheaths, wires, and catheters for ipsilateral cannulation of target visceral vessels during alignment of a fenestrated endograft. A schematic of the full technique is shown in Fig 1. The initial setup is shown in Fig 1, panel 1.

Fig 1.

Femoral flow redirection (FRED) technique for maintaining continuous passive visceral perfusion during fenestrated endovascular aneurysm repair (FEVAR). Illustration is intentionally simplified and not anatomically accurate; it is intended to demonstrate the procedural concept only. Panel 1, FRED perfusion circuit assembly. Bilateral common femoral artery access is obtained using a preclose technique. A 22F Check-Flo sheath is inserted into the common femoral artery contralateral to the main body endograft delivery. The Check-Flo hemostatic valve is modified by puncturing the valve membrane in four quadrants, allowing passage of multiple visceral sheaths through the introducer. The Check-Flo side port is connected via male-to-male Luer-lock infusion tubing to a four-port perfusion manifold (“Octopus”). Four free-flow cannulae from the manifold are connected to the side ports of the individual visceral sheaths, establishing a passive perfusion circuit as follows: blood flow through aorta → Check-Flo sheath → perfusion manifold → visceral sheaths → visceral vessels. Panel 2, Fenestrated endograft deployment and target vessel alignment. The fenestrated endograft is introduced through the contralateral femoral access and partially deployed. The visceral sheaths remain within the lumen of the endograft and are advanced through the Check-Flo sheath sequentially through the fenestrations and into the SMA and renal arteries, allowing continuous antegrade visceral perfusion while all graft fenestrations are aligned with the target vessel ostia. Perfusion is driven solely by the pressure gradient between the femoral artery and the cannulated visceral vessels, without the use of an external pump. Passive perfusion is confirmed angiographically by contrast washout and is maintained throughout the alignment process. Panel 3, Completion of repair. Panel 3a, Once satisfactory graft alignment and target vessel cannulation have been achieved, covered bridging stents are advanced through the existing sheaths into each target vessel. Panel 3b, The perfusion sheaths are then sequentially removed, and the passive perfusion circuit is disconnected. Panel 3c, The fenestrated endograft is fully deployed. Balloon molding is performed to optimize graft apposition and seal, followed by completion angiography to confirm target vessel incorporation, aneurysm exclusion, and absence of endoleak. SMA, Superior mesenteric artery.

Optional early wire cannulation of the visceral vessels may be performed to aid in identification and graft alignment. Aortic and visceral angiography is likewise optional and may be omitted when preoperative imaging is sufficient (Fig 2).

Fig 2.

Intraoperative fluoroscopic image demonstrating multivessel visceral cannulation via a 22F Check-Flo sheath during the femoral flow redirection (FRED) technique. Multiple wires and sheaths are seen selectively engaging the visceral arteries, illustrating simultaneous access to target vessels before endograft deployment and maintenance of the perfusion circuit.

Shown step by step in Fig 1, after initial setup (Fig 1, panel 1), the fenestrated endograft is introduced via the contralateral femoral artery and partially deployed (Fig 1, panel 2). The individual visceral artery sheaths are advanced through the Check-Flo sheath from the opposite limb, followed by cannulation of the target vessels from within the partially deployed fenestrated endograft. The side port of the Check-Flo sheath is connected via male-to-male Luer-lock infusion tubing to a perfusion connector with four free-flow cannulae, which are then attached to the side ports of the visceral vessel sheaths (Fig 1, panels 1 and 2). This configuration establishes a passive perfusion circuit driven by the pressure gradient between the femoral artery and the cannulated visceral arteries. Antegrade flow is confirmed angiographically by contrast washout, and continuous perfusion is maintained throughout the procedure despite the presence of cannulation hardware within the vessel lumen, without the need for external pumps or active flow regulation.

Throughout this variable period of time, the fenestrations of the graft are aligned with the ostia of all target vessels, ranging from 10 minutes to 2 hours in our experience. A sheath can remain in a visceral vessel, for example, the superior mesenteric artery, to perfuse it, while the rest of the graft is actively being fully aligned, with additional sheaths placed to perfuse the renal arteries in a sequential fashion, ensuring that once a visceral vessel sheath is placed, it is connected to the perfusion manifold to allow passive blood flow to the vessel during alignment of the remaining graft fenestrations. Once all fenestrations and visceral vessels have been appropriately cannulated and aligned, bridging stents are placed through the sheaths in the fenestrations in the endograft (Fig 1, panel 3a). Then, perfusion sheaths are removed, completing the repair (Fig 1, panel 3b). The fenestrated stent graft is then fully deployed, and a semicompliant balloon is used to optimize graft apposition and seal (Fig 1, panel 3c). A completion angiogram is performed to assess for endoleaks. Technical success is defined as successful incorporation of all target vessels with exclusion of the aneurysm. Once the setup is familiar, perfusion circuit assembly adds approximately 3 minutes and does not meaningfully prolong procedural time.

Although this report focuses on technical description rather than outcome analysis, among 15 patients treated with this technique in our practice, we observed no cases of postoperative acute kidney injury or technique-related complications. Although this report does not prove efficacy, it does demonstrate that this is a relatively simple, safe, and effective technique. Reported complication rates from the literature are included to contextualize the clinical burden of renal dysfunction after FEVAR rather than to imply outcomes specific to this cohort.

Discussion

Although FEVAR has transformed the management of complex aortic aneurysms, postoperative renal dysfunction remains a persistent limitation. Reported rates of renal insufficiency exceed 15%, even with contrast minimization strategies, suggesting mechanisms beyond contrast nephrotoxicity alone.^5,8,11

During standard FEVAR, large sheaths and catheters transiently occupy the lumen of renal and mesenteric arteries, impeding antegrade flow. Procedural complexity—such as challenging anatomy, repeated cannulation attempts, or prolonged wire manipulation—can extend ischemic time.¹² Even brief reductions in renal perfusion may result in tubular injury, particularly in elderly patients or those with limited renal reserve.¹³ The FRED technique allows continuous visceral arterial inflow through these visceral sheaths during prolonged target vessel instrumentation and endograft alignment, minimizing the period of visceral ischemia during FEVAR deployment. Visceral ischemia is a serious complication associated with repair of thoraco-AAAs. Although short periods (30 minutes or less) of visceral ischemia are generally well tolerated, increasing levels of organ dysfunction occur as this time threshold is exceeded. There is no question that visceral ischemic time should be a goal of open or endovascular thoracoabdominal aneurysm repair. In open surgery, this is accomplished through intermittent or continuous perfusion of the visceral vessels with cold electrolyte solutions of blood.¹⁴ In FEVAR, the placement of visceral sheaths can reduce or interrupt antegrade flow in the visceral vessels. FEVAR repair may be associated with significant dye load potentially augmenting any renal ischemic damage. The FRED technique provides a simple and safe option to be used during endovascular repair. Although our small series cannot show proof of reduction of ischemic events, it does show that the technique is simple, safe, and readily applied as an adjunct to FEVAR. Continuous perfusion may also enhance washout and reduce stasis, potentially mitigating ischemic and embolic injury associated with repeated catheter and wire manipulation.

Several features make the technique attractive. It is technically simple and reproducible, requiring only modification of a commonly used Check-Flo sheath without disrupting procedural workflow. The technique passively redistributes femoral arterial flow into visceral vessels through existing sheath side ports, avoiding reliance on intermittent reperfusion or rapid cannulation strategies alone. Passive flow also limits excessive pressure generation, potentially reducing endothelial injury or embolization associated with active pumping systems. In addition, the circuit can be assembled and removed quickly without additional arterial access, specialized equipment, pumps, or extracorporeal circuits.

This technique has important limitations. Additional tubing connections necessitate meticulous air elimination and strict attention to the sterile technique. Although flow rates were not directly measured, antegrade perfusion was confirmed by prompt contrast washout. Hub crowding may limit maximal flow, and quantitative assessment is challenging, as flow depends on systemic arterial pressure and resistance within the circuit. Similar to the “Octopus” visceral perfusion systems described during thoracoabdominal aneurysm repair with left heart bypass, preferential flow to lower-resistance visceral beds over the renal circulation may occur.¹⁵ Even so, partial maintenance of renal perfusion may reduce ischemic insult compared with complete luminal obstruction. Although ipsilateral lower extremity steal is theoretically possible, it is difficult to assess intraoperatively under anesthesia, and no postoperative limb ischemia or clinical signs of visceral ischemia were observed in our cohort. Future studies incorporating flow or pressure measurements may better characterize perfusion dynamics.

These findings should be interpreted cautiously given the small sample size and absence of a comparative cohort. Our experience demonstrated no postoperative acute kidney injury or clinical visceral ischemia. These findings do not prove efficacy, given the small sample size and the lack of adverse events. However, our experience shows that this is a relatively simple technique that can be safely adapted to standard FEVAR placement. Larger studies would be required to determine whether the technique meaningfully reduces renal complications or improves long-term renal outcomes. Nonetheless, the FRED technique represents a biologically plausible strategy to mitigate ischemic injury during complex fenestrated repair.

Conclusions

The FRED technique is a simple and reproducible method to maintain visceral artery perfusion during FEVAR by allowing continuous blood flow during target vessel cannulation. It may help preserve renal function, reduce ischemic injury, and support favorable postoperative recovery, warranting further evaluation in larger prospective studies.

Declaration of generative AI and AI-assisted technologies in the writing process

During the preparation of this work, the authors used ChatGPT (OpenAI) to assist in the creation of Fig 1 illustrating the stepwise components of the described technique. After use of this tool, the authors reviewed, edited, and refined the figure to ensure accuracy and clarity, and take full responsibility for the content of the publication.

Funding

None.

Disclosures

None.