Renal Chimney Research Articles

Impact of renal chimney intra-aortic stent length on branch and end-stent angle in chimney endovascular aneurysm repair and endovascular aneurysm sealing configurations.

Practice patterns and durability of parallel stent graft techniques in complex endovascular aneurysm repair (EVAR) remain poorly defined. We aimed to quantify and compare the impact of renal chimney intra-aortic stent length (IASL) on geometric deformations of renal arteries in complex EVAR. Thirty-eight nonconsecutive patients underwent EVAR utilizing parallel stent graft techniques (chimney EVAR [chEVAR], n = 28; chimney endovascular aneurysm sealing [chEVAS], n = 10) between 2010 and 2016. A total of 59 renal chimney stent grafts were used. Geometric quantification was derived from three-dimensional model-based centerline extraction. Renal chimney intra-aortic stent length (IASL) was defined as the length of chimney stent that extended from the proximal edge of the chimney stent to the ostium of the corresponding renal artery. Mean IASL for both left and right renal arteries in the cohort was 35.7mm. Renal arteries containing chimney IASL <30mm trended toward a greater branch angle (135.4 vs. 127.8°, p = .06). Left renal arteries showed significantly greater branch angle among those with IASL <40mm (135.5 vs. 121.7°, p = .045). Mean IASL for renal arteries in chEVAR was significantly longer compared to chEVAS (39.2 vs. 26.3mm, p = .003). No difference was noted in overall branch angle or end-stent angle based on procedure type. ChEVAR with IASL <30mm had significantly greater end-stent angle (48.2 vs. 33.5°, p = .03). In contrast, chEVAS patients showed no difference in end-stent angle based on IASL thresholds, but did have significantly greater branch angle among those with IASL <30mm when grouped by both all renal arteries (133.5 vs. 113.5°, p = .004) and right renal arteries (134.3 vs. 111.6°, p = .02). Renal chimney stents with longer IASL appear to exhibit less renal artery deformation, suggesting a more gradual and perpendicular transition of the chimney stent across the renal ostium.

Open repair versus EVAR with parallel grafts in patients with juxtarenal abdominal aortic aneurysm excluded from fenestrated endografting

We compared the outcomes of open surgical repair (OSR) versus endovascular aortic repair (EVAR) with parallel graft technique (PG) in patients with juxtarenal abdominal aortic aneurysm (JAAA) excluded from fenestrated endovascular aortic repair (FEVAR) due to clinical, anatomical, technical or manufacturing time reasons. A single-center analysis of consecutive patients who underwent elective and urgent (within 24-48 hours) repair of JAAA from January 2010 to January 2019 was performed. Two groups were compared: patients excluded from FEVAR and respectively treated by OSR or by PG for JAAA. Perioperative clinical, anatomic and operative data were collected in a dedicated database. The endpoints were primary technical success, changes in renal function, early and long-term mortality, freedom from aortic related reinterventions (ARRs) and aortic related mortality (ARM). Overall, 118 consecutive patients were treated for JAAA, 32 of whom (27.1%) with FEVAR. Eighty-six patients were enrolled in the study (OSR group, N.=61; PG group, N.=25). The mean age was 77.4±6.5 years for PG group and 71.1±6.7 years for OSR group (P=0.0001); the average comorbidity score of the Society for Vascular Surgery was higher for patients treated by PG (10.2±4.8 vs. 5.5±0.4, P=0.0001), with no differences for hypertension and renal score. After propensity score matching, 42 patients (27 OSR, 15 PG) without differences in the preoperative risk factors were selected. Conical shape and neck mural thrombus were respectively more represented in the OSR group (95.1% vs. 56.0%; 63.9% vs. 36.0%). Aortic clamp site was supraceliac for 12 patients (19.7%), suprarenal for 21 (34.4%) and trans-renal for 28 patients (45.9%). In the PG group, 16 patients (64%) were treated with a single renal chimney. Primary technical success was similar in the two groups (100.0% vs. 92.0%, P=0.08), with a higher rate of procedure achieved by assisted technical success for the PG group after propensity score matching analysis (20.0% vs. 0%, P=0.04). Deterioration of renal function occurred for both groups of patients, with a significant creatinine increasing 12 months after surgery in the PG group compared with OSR group (1.72±0.66 vs. 1.18±0.40, P=0.006). Multiple logistic regression shows no independent predictor of peri-operative medical complication among demographics and pre-operative relevant clinical factors between the two cohorts. No difference in terms of early mortality was observed between the groups (1.6% vs. 0%, P=1.00). At 5 years, overall survival was lower for patients treated by PG (53.5% vs. 70.2%, P=0.007), such as freedom from ARRs (64.6 vs. 90.5%, P=0.03). Freedom from ARM at 5 years did not show significant differences among the two groups (100% vs. 98.4%, P=1.00). PG represents a feasible procedure for patients excluded from FEVAR due to clinical, anatomical, technical or device manufacturing time reasons, ensuring low rates of ARM. However, ARRs during the follow-up remain the Achilles heel of this technique. OSR is still the most durable procedure in the endovascular era, allowing the treatment of proximal "hostile necks" with low rates of reoperation and a similar impact on the renal function compared to PG.

The role of surgical and total endovascular techniques in the treatment of ruptured juxtarenal aortic aneurysms.

Background: Ruptured juxtarenal aortic aneurysms (RJAAA) represent a special challenge in clinical practice, but the evidence to guide therapeutic decision-making is scarce. The aim of this study was to present two different approaches, open surgical (OAR) and chimney endovascular repair (CHEVAR), for treating patients with RJAAA. Patients and methods: This retrospective two-center study included all patients per center undergoing OAR or CHEVAR for RJAAA between February 2008 and January 2020. Juxtarenal aortic aneurysms were defined as having an infrarenal neck of 2-5 mm, measured after three-dimensional reconstruction of the computed tomography angiography scan. Results: 12 OAR patients (10 male, median age 73 years [58-90 years]) and 6 CHEVAR patients (all male, median age 74 years [59-83 years]) were included. In the OAR group, the proximal aortic clamping was suprarenal in 7 and interrenal in 5 patients. Cold renal perfusion was used in 4 patients, in 2 with suprarenal aortic clamping and in 2 with interrenal aortic clamping. 3 CHEVAR patients received a single renal chimney, the other 3 received double renal chimneys. Technical success was 12/12 in the OAR group 5/6 in the CHEVAR group. In-hospital mortality and 30-day mortality were 3/12 after OAR and 0/6 after CHEVAR. 2 OAR patients required transient dialysis. Median in-hospital stay was 14 (10-63) and 8 (6-21) days and median follow-up (FU) was 20 (3-37) and 30 (7-101) months, respectively. No further deaths occurred during FU. One OAR patient and 4 CHEVAR patients required aortic reinterventions. Conclusions: RJAAAs are rare. Both OAR and CHEVAR can represent adequate treatments for RJAAAs. OAR is the traditional approach, but CHEVAR has - in a high-volume center - promising early results with nonetheless a need for continuous FU to prevent reinterventions. Defining the studied aortic pathology precisely is essential for future research in order to draw valid conclusions.

In Vitro Evaluation of Balloon-Expandable Chimney Grafts in the Renal Arteries Combined With the Endurant Endograft

Purpose: To compare balloon-expandable covered stents (BECS) available for use as renal chimney grafts to the Advanta V12 approved for use with the Endurant endograft. Materials and Methods: A silicone model was manufactured based on preoperative computed tomography angiography (CTA) scans of a patient with a 7-cm juxtarenal aneurysm treated with an Endurant bifurcated endograft and an Advanta V12 covered stent for the 6-mm-diameter right renal artery. The model was placed in a flow box filled with a 37°C blood-mimicking solution equipped with a pulsatile pumping system (140/60 mm Hg). The tested BECS were the Advanta V12, the VBX, and the BeGraft+. A 36-mm-diameter Endurant II endograft with a 16-mm-diameter contralateral limb and a 6×59-mm BECS chimney graft were used in 9 consecutive tests (3 for each combination). After each implantation, the model was placed in the CT scanner, and 2 radiologists blinded to the test device independently measured the gutter areas and the patent chimney graft lumen at the level of the Endurant’s suprarenal stent, at the level of the chimney’s maximum curvature, and 10 mm inside the renal artery. The intraclass correlation coefficients (ICC) were calculated to assess interreader reliability. Results: The mean gutter areas were 19.3±7, 20.2±8, and 22.3±8 mm2 for the Advanta, VBX, and BeGraft+, respectively (all p>0.05). At the level of the aortic endograft’s suprarenal stent struts, the mean diameter of the Advanta V12, VBX, and BeGraft+ were 4.46±0.3, 4.12±0.4, and 4.12±0.3 mm, respectively (all p>0.05). At the level of the maximum chimney graft angulation, the mean diameters were 3.77±0.3, 4.16±0.1, and 3.74±0.3 mm, respectively (all p>0.05). In the right renal artery, the mean diameters were 3.91±0.2, 4.05±0.9, and 4.3±0.4 mm, respectively (all p>0.05). The ICCs varied between 0.7 and 0.9, indicating good agreement between readers. Conclusion: These in vitro findings showed comparable results between the Advanta V12 and the available BECS used in conjunction with the Endurant endograft according to the instructions for use. Further clinical evaluation is needed to confirm these results.

CTA Assessment of Midterm Morphological Changes to Chimney Grafts Used in the Treatment of Juxtarenal Aortic Aneurysms

Purpose: To evaluate chimney stent-graft position and morphological changes of the aneurysm sac as visualized by postoperative computed tomography angiography (CTA) over a minimum 24-month follow-up period. Materials and Methods: Twenty-one patients (mean age 75.7±8.6 years; 20 men) with juxtarenal aortic aneurysms who underwent successful chimney endovascular aneurysm repair (ch-EVAR) with the Endurant stent-graft and had 2 postoperative CTAs separated by at least 24 months were included in the study. CTA-based measurements of aortic stent-graft migration, target vessel angle, and chimney angle were compared between the serial scans. Results: During a mean follow-up of 34.9 months (range 24–69.2), the mean migration of the aortic stent-grafts was under 5 mm (2.76±2.4 mm). The average migration distance per year was 1.15 mm. The aneurysm diameter reduced a mean 3.25 mm (p=0.048). The right renal artery angle moved significantly upward 6.72° (p=0.025), while the right renal chimney stent-graft moved significantly downward 7.83° (p=0.042). The left renal artery angle also moved upward 1.87° (p=0.388) and the corresponding chimney moved downward 5.68° (p=0.133). During the study period, no type I/III endoleak or chimney occlusion was observed. Conclusion: Midterm morphometric assessment of ch-EVAR using CTA showed significant aneurysm sac shrinkage and a stable 3-year position of the abdominal devices, with the mean downward migration of the aortic stent-graft being <5 mm in the majority of cases. The chimney grafts seem to be prone to take an oblique rather than parallel configuration during follow-up. However, there was no relevant clinical consequence related to this phenomenon.

Endovascular Exclusion of Abdominal Aortic Aneurysms and Simultaneous Resection of Colorectal Cancer

No consensus exists on the optimal strategy for treatment of abdominal aortic aneurysm (AAA) associated with colorectal cancer (CRC). The purpose of this study was to evaluate the results of endovascular treatment of AAA with simultaneous resection of CRC. Twenty-two consecutive patients presenting with AAA associated with a CRC were treated by endovascular AAA exclusion and simultaneous CRC resection. Median diameter of the aneurysm was 6.5cm (range, 4.8-8cm). Two patients (9%) had grade I cancer, 5 patients (23%) grade II, 13 patients (59%) grade III, and 2 patients (9%) grade IV. The 2 surgical procedures were performed under the same general anesthesia. Aneurysm exclusion was achieved using an infrarenal aorto-bi-iliac endoprosthesis (13 patients) and using an aorto-bi-iliac endoprosthesis with suprarenal fixation (9 patients), with 1 patient receiving bilateral renal chimney stent implantation. In all cases, vascularization of the hypogastric arteries was preserved. After AAA exclusion, colic resection was carried out by laparotomy with right colectomy (7 patients) and anterior rectocolic resection (15 patients). In all patients, AAA exclusion was controlled by a computed tomographic angioscan (CTA) at 1 month and duplex ultrasound every 6 months, and at some later stage, it was through inclusion of CTA as part of oncology surveillance. The mean duration of follow-up was 42months (10-120months). The primary endpoint was composite and regrouped any death occurring during the first 30days after procedures, any type I endoleak, any aortic reintervention, and any AAA-related mortality. No patient died during the first 30 postoperative days, and no patient was lost to follow-up. No aortic endoprosthesis infection and no type I endoleak were observed. Five endoleaks arising from the lumbar arteries (n=4) or from the inferior mesenteric artery (n=1) were identified. As they were not associated with an increase of the AAA diameter >5mm, they were not treated. 1 colic anastomotic leak and 2 incisional abscesses were successfully cured by local care only. Nine patients (41%) died of cancer evolution during the follow-up period. In this series, treatment of AAA and CRC during the same operative session yields results comparable to those observed when surgery is performed in 2 distinct operative sessions. Synchronous treatment reduced waiting time of colic resection. It may also shorten total hospitalization duration, although this last hypothesis is not supported by comparison with a control group.

Polar orientation of renal grafts within the proximal seal zone affects risk of early type IA endoleaks after chimney endovascular aneurysm repair

ObjectiveThe objective of this study was to describe the polar orientation of renal chimney grafts within the proximal seal zone and to determine whether graft orientation is associated with early type IA endoleak or renal graft compression after chimney endovascular aneurysm repair (ch-EVAR). MethodsPatients who underwent ch-EVAR with at least one renal chimney graft from 2009 to 2015 were included in this analysis. Centerline three-dimensional reconstructions were used to analyze postoperative computed tomography scans. The 12-o'clock polar position was set at the takeoff of the superior mesenteric artery. Relative polar positions of chimney grafts were recorded at the level of the renal artery ostium, at the mid-seal zone, and at the proximal edge of the graft fabric. Early type IA endoleaks were defined as evidence of a perigraft flow channel within the proximal seal zone. ResultsThere were 62 consecutive patients who underwent ch-EVAR (35 double renal, 27 single renal) for juxtarenal abdominal aortic aneurysms with a mean follow-up of 31.2 months; 18 (29%) early type IA “gutter” endoleaks were identified. During follow-up, the majority of these (n = 13; 72%) resolved without intervention, whereas two patients required reintervention (3.3%). Estimated renal graft patency was 88.9% at 60 months. Left renal chimney grafts were most commonly at the 3-o'clock position (51.1%) at the ostium, traversing posteriorly to the 5- to 7-o'clock positions (55.5%) at the fabric edge. Right renal chimney grafts started most commonly at the 9-o'clock position (n = 17; 33.3%) and tended to traverse both anteriorly (11 to 1 o'clock; 39.2%) and posteriorly (5 to 7 o'clock; 29.4%) at the fabric edge. In the polar plane, the majority of renal chimney grafts (n = 83; 85.6%) traversed <90 degrees before reaching the proximal fabric edge. Grafts that traversed >90 degrees were independently associated with early type IA endoleaks (odds ratio, 11.5; 95% confidence interval, 2.1-64.8) even after controlling for other device and anatomic variables. Polar orientation of the chimney grafts was not associated with graft kinking or compression (P = .38) or occlusion (P = .10). Takeoff angle of the renal arteries was the most significant predictor of chimney graft orientation. Caudally directed arteries (takeoff angle >30 degrees) were less likely to have implanted chimney grafts that traversed >90 degrees in polar angle (odds ratio, 0.09; 95% confidence interval, 0.01-0.55). ConclusionsRenal chimney grafts vary considerably in both starting position and their polar trajectory within the proximal seal zone. Grafts that traverse >90 degrees in polar angle within the seal zone may be at increased risk of early type IA endoleaks and require more frequent imaging surveillance. Caudally directed renal arteries result in a more favorable polar geometry (eg, cranial-caudal orientation) with respect to endoleak risk and thus are more ideal candidates for parallel graft strategies.

Impact of Renal Chimney Grafts on Anatomical Suitability for Endovascular Repair in Ruptured Abdominal Aortic Aneurysm

Purpose: To evaluate the impact of renal chimney grafts on anatomical suitability for endovascular aneurysm repair (EVAR) in ruptured abdominal aortic aneurysm (rAAA). Methods: Contrast-enhanced computed tomography images of 206 patients with rAAA [175 men (mean age 75±7.8 years) and 31 women (mean age of 76±7.5 years)] were evaluated in a dedicated 3-dimensional vascular workstation. Assessment of infrarenal EVAR suitability was based on predefined anatomical variables reflecting the Instructions for Use of commercially available stent-grafts. In patients where aneurysm neck length was the only limiting factor for suitability, reevaluation of the proximal sealing zone was done, accounting for chimney grafts in one or both renal arteries. Results: Seventy (34%) rAAA patients were anatomically suitable for EVAR: 65 (37%) of 175 men and 5 (16%) of 31 women (p<0.01). Eighty-nine (65%) of the 136 unsuitable patients had aneurysm necks <15 mm long; short neck was the only exclusion criterion in 33 (24%) cases. In the 33 short-necked aneurysms without other limiting factors, a proximal sealing zone >15 mm could potentially be achieved with one or two renal chimney grafts in 12 (36%) and 25 (76%) patients, respectively, increasing overall suitability to 40% and 46%. If access issues could also be solved and a similar strategy with chimneys for the renal arteries was applied, the EVAR suitability would increase further to 58%. Conclusion: Roughly one third of patients with rAAA are anatomically suitable for EVAR; short aneurysm neck is the most common exclusion criteria. In appropriate cases, chimney grafts in one or both renal arteries may increase overall suitability by 12%. Suitability increases to ~60% when iliac access issues are additionally overcome.

Endovascular Thrombectomy of a Renal Artery Chimney Stent-Graft Using the Solitaire Recanalization Device

The chimney graft technique is gaining popularity as an alternative endovascular treatment for juxtarenal aneurysms not suitable for standard or fenestrated endovascular aneurysm repair (EVAR).1–6 Despite excellent technical success,1,3–6 limited data are available regarding the long-term effectiveness of the technique, particularly in terms of chimney stent occlusion. This complication may have catastrophic consequences and represents a challenge for any endovascular approach, requiring in most the cases an open surgical bypass to restore vessel patency. Donas et al.1 used open thrombectomy to treat a renal chimney graft thrombosis. We encountered a symptomatic acute thrombosis of a renal chimney stent-graft, which we successfully treated with endovascular thrombectomy using a recanalization device that, in a recent article in the JEVT, proved useful in treating acute popliteal thrombosis.7

The Chimney Technique in Endovascular Aortic Aneurysm Repair: Late Ruptures After Successful Single Renal Chimney Stent Grafts

The chimney graft technique has been proposed as an alternative endovascular treatment of juxtarenal aortic aneurysms, extending the landing zone and enabling successful exclusion of the aneurysm with standard endograft devices. A prospective observational study assigning patients with juxtarenal aortic aneurysm treated with single renal chimney grafts in a tertiary vascular center in the United Kingdom was conducted. Primary outcome endpoints were defined as technical success, perioperative morbidity and mortality, and freedom from any type of endoleak, reintervention, and aneurysm-related death. Nine patients were enrolled. Successful aortic and chimney graft implantation was achieved in all patients. A proximal type I endoleak noticed on completion angiogram was treated with an aortic extension cuff. None of the patients died within 30 days of treatment. Two patients developed a type IA endoleak during follow-up, resulting in aneurysm rupture and death. Both patients had had uneventful chimney procedures, and no endoleak was evident on previous surveillance computed tomographic scans. All chimney grafts remained patent, and none of the patients developed renal impairment during the follow-up period. Proximal type I endoleak constitutes a weak point of chimney graft interventions. Increased vigilance in surveillance of such patients to prevent late aneurysm-related complications is required. Additional research to identify potential poor prognostic morphologic indicators is expected.