Percutaneous Repair of an Abdominal Aortic Aneurysm with Left Renal Artery Involvement Using the Snorkel Graft Technique: A Case Study

Patient Presentation

A 66-year-old male presented with a history of abdominal pain, hypertension, hyperlipidemia, and known coronary artery disease. Physical examination demonstrated a pulsatile abdominal aorta. 

Contrast-enhanced computed tomography (CTA) demonstrated a 9 x 5.5 cm fusiform abdominal aortic and iliac aneurysm (Figures 1-3). The aneurysm involved the left renal artery (Figures 1 and 3) and extended into the bilateral common iliac arteries. After consultation with the interventional cardiologist, it was determined that the patient would undergo a percutaneous endovascular aneurysm repair (EVAR) with a snorkel graft to preserve the left renal artery. 

Pre-procedurally, a descending aortagram with bilateral femoral artery runoff was performed with a pigtail catheter marked at 1 cm intervals to size the EVAR graft (Figure 4). It also allowed the physician to study the visceral, renal and iliac arteries in greater detail. The descending aortagram was remarkable, because of the difference between the CTA and angiogram in defining the true size and clinical significance of the aneurysm (Figures 1, 2, 4).

EVAR with the Snorkel Procedure

For this procedure, the patient was consented, given general anesthesia, intubated and provided with airway management support by the anesthesia department. The left arm and bilateral groins were prepped and draped in sterile fashion, and local anesthesia was administered prior to gaining arterial access. In order to deliver the left renal artery snorkel graft and repair the abdominal aortic aneurysm (AAA), it was necessary to access the left brachial artery and both femoral arteries. For the upper extremity, a 6 French (Fr) short arterial sheath was initially introduced into the left brachial artery via a micropuncture system, and a 5 Fr Cobra catheter (Cook Medical) was advanced into the abdominal aorta over a wire. Bilateral percutaneous femoral arterial access was then achieved, with 8 Fr short sheaths. To ensure non-surgical post-procedural hemostasis with these large caliber sheaths, three Perclose devices (Abbott Vascular) were preset to close the left femoral puncture site, and two Perclose devices were preset to close the right femoral artery puncture site.¹ A 12 Fr sheath was placed in the right femoral artery and an expandable 8 Fr SoloPath sheath² (Onset Medical) was placed in the left femoral artery. 

The SoloPath expandable sheath was chosen because it can be expanded to 19 Fr during the procedure, offering the physician greater flexibility in using the percutaneous method to deliver devices such as AAA stent grafts. In this case, the left femoral system was inflated up to 19 Fr. Once expanded, the left femoral sheath was large enough to provide delivery of the Gore Excluder graft body that was introduced into the abdominal aorta and left iliac arteries. The 12 Fr right femoral sheath was used to deploy the contra-lateral (right) iliac limb of the graft.

After initial access, the patient was heparinized with 5000 units and an activated clotting time (ACT) of 254 was confirmed. The AAA stent graft with snorkel graft procedure was then performed. The snorkel graft technique involves the deployment of a self-expanding stent in the renal artery, and then the deployment of a self-expanding abdominal aorta graft. The renal stent is positioned so that the proximal edge extends slightly into the abdominal aorta, so the aortic graft does not occlude or compress the renal graft. Following the deployment of both grafts, they are post dilated with kissing balloon angioplasty to fully oppose the stent graft.

To deliver the snorkel graft to the left renal artery, the 6 Fr short sheath in the brachial artery was exchanged for a 7 Fr, 90 cm Destination sheath (Terumo), which extended into the abdominal aorta. The left renal artery was accessed with a 6 Fr JB1 catheter and guide wire. The guide wire was exchanged for a Super Stiff Amplatz wire (Boston Scientific) and a 6 mm x 38 mm iCast (Atrium Medical) covered stent was positioned in the left renal artery.

At this point, a 31 mm x 14.5 mm x 15 cm graft was advanced over a wire and deployed in the abdominal aorta and left common iliac artery at 8 atmospheres of pressure. A kissing technique was used to deploy the left renal graft and fully dilate the abdominal graft (Figure 5), which slightly covered the ostium of the left renal artery. The contra-lateral limb (right iliac) was then grafted with a 14.5 mm x 12 cm Excluder system (Gore), which was then fully deployed. After deployment of the graft, the aorta and snorkel graft were post dilated using the kissing technique, and the aorta and iliac artery sections were also post dilated. The final result revealed a widely a patent left renal artery stent, as well as an abdominal aorta and bilateral iliac artery stents with no endoleaks (Figures 6-7).

Following the procedure, the bilateral groin sheaths were removed and excellent hemostasis was achieved by deploying the preset Perclose devices. The left brachial sheath was removed post catheterization, after protamine administration, and a normal ACT of 154 was recorded. The procedure was technically and clinically successful, and the patient was hemodynamically stable throughout. 

Post EVAR, the patient was extubated without complication and the heparin effect was reversed with protamine. Following protamine administration, bilateral femoral artery hemostasis was achieved with the preset Perclose devices. The left brachial artery sheath was removed with manual hemostasis and the patient was transported to his room.

Patient Outcome

The patient had no complications from the initial EVAR procedure. However, post-procedurally, he did develop a thrombus and diminished pulse in the left arm, which required a thrombectomy.  Thrombectomy was performed via the brachial artery by creating a focal arteriotomy, and removing a focal brachial artery thrombus with a Fogarty catheter (Edwards Lifesciences). The site was then closed with a small vein patch, and full circulation was restored to the left upper extremity. The patient fully recovered and was routinely discharged two days post-EVAR with normal circulation in the left upper extremity. 

He was clinically reevaluated and had a CTA six weeks post EVAR. The results revealed well-deployed and widely patent abdominal, left renal artery and iliac grafts, with no evidence of endoleaks (Figures 8-9). The left upper extremity had no residual side effects from the thrombectomy and the patient is asymptomatic. He will receive routine follow-up again in six months.

Since this procedure, a second patient has had a renal snorkel graft with percutaneous EVAR and this procedure was technically and clinically successful. In this case, the upper extremity was evaluated in more detail, and extra precautions were taken to prevent thrombus formation. This included the use of a radial artery cocktail of verapamil, heparin and nitroglycerin, pre-procedural ultrasound and continuous arterial line infusion throughout the procedure.

Discussion

The snorkel technique consists of placing parallel stents or stent grafts adjacent to the endograft main body to maintain perfusion to renal, visceral or internal iliac branches after aneurysm exclusion. It can be also used as bailout from accidental coverage of vital side branches during deployment requiring close approximation of the main body to the branch artery in question, or for the intentional cranial relocation of the EVAR seal zone for juxtarenal aortic aneurysms. The snorkel technique with EVAR offers a viable, non-surgical option for AAA repair that requires the protection of renal, visceral or internal iliac arteries.  

Shuja and Kwolek provide a valuable overview of snorkel and chimney graft techniques that suggests snorkel grafts are an attractive option for high-risk surgical candidates, emergent aneurysm repair, and high-risk aneurysms involving paravisceral vessels.³ This data is supported by Lee, Greenberg and Dalman from the Stanford University Medical Center, who studied the placement of 56 snorkel grafts in 28 patients with juxtarenal aneurysms. Snorkel grafting of the renal artery offers an option for high-risk surgical patients, whose short-term morbidity and mortality rates and in-hospital time would be greatly increased by the complexity of open surgical AAA repair with renal or visceral artery involvement.⁴

Numerous clinical trials, including EVAR 1⁵, DREAM⁶, and OVER⁷ have been performed to evaluate efficacy of EVAR versus open AAA repair. These trials suggest that EVAR compares favorably to open surgical repair for AAA. It reduces inpatient hospital time, short-term morbidity and mortality, and requires no open surgical incision of the abdomen. Long term, it has morbidity and mortality rates that are similar to open surgery at five years. According to these trials, EVAR does require more vigilant follow-up protocols and there were more latent post-EVAR procedures that needed to be performed compared to the open surgery group. However, this does not take into account complex aneurysm repair that involves major branch vessels or the advancement of technology that makes percutaneous delivery a viable option. 

Additionally, the EVAR 2 trials, which compared non-surgical candidates for no treatment versus EVAR, showed a clear advantage of performing EVAR in this patient group. This makes EVAR an attractive option for non-surgical candidates, and according to a recent French study on EVAR 2, EVAR 2 justifies the endovascular repair of AAAs in high risk, non-surgical subsets, and emphasizes the importance of a multi-disciplinary treatment for high-risk patients in high-volume centers.⁸ 

With the emergence of the snorkel technique, the role of EVAR has expanded further and can be used for high-risk patients whose renal, visceral arteries or internal iliac arteries are jeopardized in the EVAR process. Presently, there are also clinical trials underway to evaluate the use of fenestrated grafts for AAA repair that involve the renal and visceral arteries. With advancements in technology and increased operator experience, there is vast potential for complex EVAR repairs. 

Additionally, the ability to perform EVAR with a percutaneous-only approach has improved patient comfort and further reduced patient inpatient hospitalization times and surgical complications: infections, hemorrhage, and neuropathies. It allows the physician to gain access and hemostasis in a similar fashion to coronary artery intervention, especially with the use of preset Perclose devices. Advances in technology, like the SoloPath sheaths, smaller and better delivery systems, and increased operator experience, offer vast potential to perform many more EVAR repairs percutaneously. 

Conclusion

Percutaneous EVAR with the snorkel graft technique offers high-risk aneurysm patients new treatment options. The advantages of percutaneous EVAR include decreased likelihood of infection, shorter inpatient admission times, no surgical incisions, and reduced morbidity and mortality rates in the short term. The snorkel graft technique also allows interventionalists to repair aneurysms that traditionally required high-risk open surgery. Initial data, although limited, has shown that the snorkel technique has been highly successful in the short term, and offers safer and less invasive means to treat this patient group. With more advanced technology and increased operator skill, this technique offers vast potential for the management of complex AAAs and has already proven itself to be a viable, frontline treatment for select groups of patients.  

The authors can be contacted via Richard Merschen at richardmerschen@verizon.net.

This article received a double-blind peer review from members of Cath Lab Digest’s editorial board.

Disclosure: The authors report no conflicts of interest regarding the content herein.

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