F/b-EVAR arguably represents the best endovascular option for patients with failed previous EVAR. However, this technique can be challenging for several reasons. First, the working length between the lowest renal artery and the flow divider of the existing graft is often too short to accommodate currently approved Z-fen configurations. Second, discrepancy in size between the failed device and the fenestrated device often makes achieving a seal problematic. Third, the ability to rotate and accurately deploy the fenestrated device inside the patient can be severely compromised by vessel tortuosity and friction between devices. Lastly, cannulation of target vessels can be difficult, especially in patients with suprarenal fixation. These challenges, in part, accounted for the higher than our previously reported average fluoroscopy time (61 min) and dose (1097 mGy) with this procedure (Manunga et al., 2018).
Twelve (62.3%) patients in our cohort required complete relining (Z-fen+ bifurcated device + iliac limbs) in order to achieve a seal. This process was facilitated by creation of an inverted limb in 5 patients. While the technique of inverted limb has previously been described (Martin et al., 2014; Jain et al., 2016), two key differences deserve mentioning. First, devices used in recent series were custom-made by the industry while inverted limbs used in our cohort were surgeon-modified. Second, the main body of industry-made devices has two sealing stents whereas our devices had three sealing stents and, therefore, allowed for a longer overlap. Creation of an inverted limb shortens the distance between the top of the graft and the gate of the shortest distal cook bifurcated main body graft from 76 mm to 51 mm. Using this technique in a patient with a distance from the lowest renal artery to the flow divider of < 49 mm may result in “jailing” of the gate.
While not utilized in this cohort, alternatives to inverted limb include the use of an AUI device or a Gore IBE. The use of AUI devices has a disadvantage of long-term femoral to femoral bypass graft occlusion and decreased pelvic flow. The IBE has a main body diameter of 23 mm and a distance from the top of the graft to the gate of 55 mm. If one opts on using this device, the repair needs to be built from the bottom up – the IBE is placed first, followed by implantation of the fenestrated device – to obtain a seal since the distal fenestrated device is 24 mm in diameter.
Rescuing a failed AUI device with f-EVAR is feasible and requires the use of preload wires on the fenestrated device. We prefer using the 65 cm, 12 French Gore DrySeal (L.W. Gore, Flagstaff, AZ, USA) in the axillary artery and cannulating target vessels from the arm access. We do not advocate releasing diameter reducing ties before securing target vessels as doing so would almost certainly make cannulation of target vessels extremely difficult, if not impossible.
Converting various devices to a fenestrated repair present different set of challenges. The distance between the top of the graft to the flow divider in a Gore excluder is device size dependent and ranges from 40 to 60 mm. In our experience, a failed excluder tends to migrate down, allowing for ≥ 20 mm in additional working length. This makes complete device relining feasible in most cases. Medtronic Talent and Cook endografts have longer main bodies and tend to migrate less. However, they have suprarenal struts that might make placement of bridging stents difficult. This was the case with the single patient in our cohort that required a laparotomy.
Our treatment philosophy in younger patients, those with failed EVAR or family history of aneurysmal disease differs from that of patients without this history. In the above population, we strive to maximize the aortic neck by incorporating all 4 visceral arteries whenever feasible. However, the need for a longer sealing zone needs to be balanced with the risks of paraplegia. We routinely analyze and minimize the number of intercostal arteries covered by the repair in order to mitigate the risk of paraplegia. Furthermore, we strive to keep lower extremity ischemia time short and use spinal drains and neuromonitoring in all patients undergoing > 2 cm coverage of the aorta above the celiac artery.
Understanding the reason for primary treatment failure is crucial. In the series from Katsargyris et al., EVAR failure in all 26 patients was attributed to low initial stent-graft implantation in 27% of patients, short initial neck in 19%, undersized initial stent-graft in 8%, stent graft migration and disease progression in 23%, respectively (Katsargyris et al., 2013). In the Austria series, treatment failure was attributed to type I endoleak in 58.3% patients, stent graft migration in 16.7% and disease progression in 25% (Falkensammer et al., 2017). In the Cleveland clinic series, treatment failure was attributed to type IA endoleak in 70.4% of patients, stent migration in 33.3% and neck degeneration in 14.8% with some patients having a combination of these factors (Falkensammer et al., 2017). Wang et al. attributed treatment failure in a series of 12 patients to neck enlargement after open repair in 6, type IA endoleak in 5 and neck enlargement in 1 patient post EVAR (Wang et al., 2018). In our series, type IA endoleak was observed in 94.7% of patients with stent graft migration accounting for 47.4% of primary treatment failure, disease progression for 26.3% and short neck for 15.8%. The underlying theme of the above studies remains the same – most EVARs fail because of loss of proximal seal, which is the consequence of disease progression or implantation of the device in a hostile neck.
Sixteen patients (84.2%) in this cohort required a thoracoabdominal repair with spinal drain and neuromonitoring. Even with this complex reconstruction, most patients were discharged home within 3 days of their surgery. This, in our opinion, validates the advantage of endovascular intervention over open surgical repair in this patient population (Perini et al., 2019; Arnaoutakis et al., 2019; Klonaris et al., 2014; Nabi et al., 2009).
MAEs occurred in three patients (15.7%). The first patient underwent a successful exclusion of the aneurysm but developed bilateral lower extremity compartment syndrome overnight and required fasciotomies. He was on dialysis for 2 weeks prior to normalization of his renal function. The second patient was an octogenarian with a ruptured aneurysm treated with a 3 vessel fenestrated device. He developed paraplegia postoperatively after suffering an episode of hypotension. A spinal drain was placed, all antihypertensive medications discontinued and mean arterial pressure (MAP) raised with no improvement. He required reintubation because of fluid overload and expired shortly thereafter. The last patient required a laparotomy due to inability to advance sheaths needed to place bridging stents. This was likely due to the presence of suprarenal struts spanning the orifice of renal arteries that prevented passage of anything bigger than a 0.035 wire.
The inability to cannulate renal arteries was a common issue with this procedure and is likely related to access vessels tortuosity, suprarenal struts and the friction between the fenestrated device and the failed implant. In the Cleveland Clinic experience, technical success rate was 85%; early mortality 3.8% and target vessel perfusion rate was 92%. Seven patients lost their kidneys due to inability to cannulate renal arteries. Another patient lost a celiac artery due to dissection [10]. There were no early deaths in the Katsargyris et al. cohort. However, difficulty in target vessel catherization was encountered in 23.1% of patients, resulting in the loss of 4 target vessels and a successful cannulation rate was 94.6% (Katsargyris et al., 2013). In the series from Austria, technical success rate was 58.3%. Two celiac arteries were lost during cannulation but both remained asymptomatic (Falkensammer et al., 2017). Our technical success rate of 95%, target vessels incorporation of 97.3%, early (in hospital) and late reintervention rate of 15.5% and 5.3%, respectively, long-term target primary vessel patency of 98.6% and primary assisted patency rate of 100% compares favorably to results from these series (Katsargyris et al., 2013; Falkensammer et al., 2017; Martin et al., 2014; Wang et al., 2018). The single death in our series occurred in a patient treated for a rupture. The above three reports included only electively treated patients and, to our knowledge, none of the currently published series on this topic included patients treated on an emergency basis.
The use of surgeon-modified devices remains an important part of any aortic center as industry-made custom devices take weeks to manufacture and off-the-shelf devices currently being investigated only fit limited patients’ anatomy. Modification of the alpha graft can be challenging due to the presence of laser-cut proximal barb that prohibits retrograde resheathing of the device. Some people have resorted to cutting proximal barbs during modification. However, doing so might compromise the integrity of the device. Instead, we described a technique of transitioning the modified alpha graft through a series of peel away sheaths prior to loading it into its original sheath (Manunga, 2018). This approach remains necessary when treating aortic arch pathologies. When used to treat thoracoabdominal aneurysms or failed EVAR, we found it easier to use the newly released 65 cm Gore DrySeal sheath to deliver the surgeon-modified alpha device. In this case, the device is only transitions through one peel away sheath before going into the previously place Gore DrySeal sheath. Once in place, the sheath is pulled back to deploy the device. This technique eliminates the challenging step of introducing the modified Alpha stent graft into its original sheath.
The current study has several limitations. First, f/b-EVAR is only one of two endovascular options for failed EVAR. The use of parallel grafts, especially when incorporating 1 or 2 vessels, has an important role in the treatment of these patients (Donas et al., 2015). This is particularly true in the United States and other parts of the world where access to device customization is limited. Second, our center has a good experience with f-EVAR as a large number of patients have been treated with this technology over the last 5 years. As such, our results might not be reproducible. Nonetheless, our experience is unique in several ways. First, 84% of included patients underwent a thoracoabdominal repair. Second, the study included both elective and emergently treated patients. Third, we did not rely on the industry for further device customization. Instead, we ordered device within the current FDA regulations and slightly modified them to fit the purpose.
