Impact of alterations in target vessel curvature on branch durability after endovascular repair of thoracoabdominal aortic aneurysms

Renovisceral artery alterations due to branched endovascular aortic repair and respiratory-induced deformations

OBJECTIVE

This study quantified respiratory-induced dynamics of branch vessels before and after thoracoabdominal aortic aneurysm (TAAA) branched endovascular aneurysm repair (bEVAR).

METHODS

Patients with TAAA were recruited prospectively and treated with bEVAR, predominantly with Zenith t-Branch and BeGraft Peripheral PLUS bridging stents. Using SimVascular software, three-dimensional geometric models of the vessels and implants were constructed from computed tomography angiograms during both inspiratory and expiratory breath-holds, preoperatively and postoperatively. From these models, branch take-off angles, end-stent angles (transition from distal end of stent to native artery), and curvatures were computed. Paired, two-tailed t tests were performed to compare inspiratory vs expiratory geometry and pre- vs postoperative deformations.

RESULTS

We evaluated 52 (12 celiac arteries [CA], 15 superior mesenteric arteries [SMA], and 25 renal arteries [RA]) branched renovisceral vessels with bridging stents in 15 patients. Implantation of bridging stents caused branch take-off angle to shift inferiorly in the SMA (P = .015) and RA (P = .014) and decreased the respiratory-induced branch angle motion in the CA and SMA by approximately 50%. End-stent angle increased from before to after bEVAR for the CA (P = .005), SMA (P = .020), and RA (P < .001); however, respiratory-induced deformation was unchanged. Bridging stents did not experience significant bending owing to respiration.

CONCLUSIONS

The decrease in respiratory-induced deformation of branch take-off angle from before to after bEVAR should decrease the risk of device disengagement and endoleak. The unchanging respiratory-induced end-stent bending, from before to after bEVAR, means that bEVAR maintains native vessel dynamics distal to the bridging stents. This factor minimizes the risk of tissue irritation owing to respiratory cycles, boding well for branch vessel patency. The longer bridging stent paths associated with bEVAR may enable smoother paths subject to less dynamic bending, and potentially lower fatigue risk, compared with fenestrated EVAR.

Aortic hemodynamic and morphological analysis before and after repair of thoracoabdominal aortic aneurysm using a G-Branch endograft

Background and objective: The G-Branch endograft is a novel multibranched "off-the-shelf" device used to repair thoracoabdominal aortic aneurysms (TAAAs). This report describes the hemodynamic and morphological performance of the G-Branch endograft in a human patient with TAAA. Materials and methods: We retrospectively reviewed the computed tomography angiography scans and clinical data of a woman in whom TAAA was treated using a G-Branch endograft. Patient-specific three-dimensional models were reconstructed, and computational fluid dynamics and morphological and hemodynamic indicators were analyzed before and after implantation of the device. Results: From a morphological perspective, there was an increase in cross-sectional area in the G-Branch endograft and all bridging stent grafts over time. Blood flow was redistributed among the renovisceral arteries, with a decrease in flow rate in the celiac artery and an increase in the left renal artery. Laminar blood flow was smoother and more rapid after implantation of the G-Branch device and remained stable during follow-up. In the bridging stent grafts, flow recirculation zones were found in the bridging zones of the celiac artery and superior mesenteric artery as well as the distal sealing zones of both renal arteries. Furthermore, higher time-averaged wall shear stress and a lower oscillatory index and relative resident time were found in the G-Branch endograft and bridging stent grafts. Quantitative analysis showed obvious reduction in the surface area ratio of the elevated time-averaged wall shear stress area and surface area ratio of the relative resident time after G-branch implantation. Conclusion: The revascularization of branch vessels occurred following G-branch implantation, with improvements arising not only from morphological changes but also from hemodynamic alterations. The long-term performance of the G-Branch endograft needs further investigation and clinical validation.

Effect of bridging stent graft selection for directional branches on target artery outcomes of fenestrated-branched endovascular aortic repair in the United States Aortic Research Consortium

OBJECTIVE

The purpose of this study was to evaluate the effect of directional branches (DBs) bridging stent choice on target artery (TA) outcomes during fenestrated-branched endovascular repair of complex abdominal and thoracoabdominal aortic aneurysms.

METHODS

Patients enrolled in nine prospective physician-sponsored investigational device exemption studies in the United States between 2005 and 2020 were analyzed. All patients who had at least one TA incorporated by DB using either self-expandable (SESGs), balloon-expandable (BESGs), or hybrid stent graft combinations (HSGs). Endpoints were TA patency and freedom from TA endoleak, instability, and reintervention.

RESULTS

There were 800 patients with 2426 renal-mesenteric arteries incorporated by DBs. DB stent selection was SESGs in 1205 TAs (50%), BESGs in 1095 TAs (45%), and HSGs in 126 TAs (5%). SESGs were predominantly used in the first three quartiles of the study period, whereas BESGs comprised 75% of all stents between 2017 and 2020. The median follow-up was 15 months (interquartile range, 6-35 months). At 5 years, BESGs had significantly lower freedom from TA instability (78% ± 4% vs 88% ± 1% vs 96% ± 2%; log-rank P =.010), freedom from TA endoleaks (87% ± 3% vs 97% ± 1% vs 99% ± 1%; log-rank P < .001), and freedom from TA reintervention (83% ± 4% vs 95% ± 1% vs 99% ± 2%; log-rank P <.001) compared with SESGs or HSGs, respectively. For renal arteries, there was no difference in freedom from TA instability for BESGs, SESGs, or HSGs. However, freedom from TA endoleaks and reintervention were lower for renal arteries targeted by BESGs compared with DBs targeted by SESGs and HSGs (83% ± 6% vs 98% ± 1% vs 100%; log-rank P < .001; and 70% ± 10% vs 92% ± 1% vs 96% ± 4%; log-rank P = .022). For mesenteric arteries, DBs targeted by BESGs had lower freedom from TA instability, endoleak, and reintervention than SESGs or HSGs. In stent-specific analysis, iCAST BESGs had the lowest freedom from TA instability either for renal or mesenteric arteries, primarily due to higher rates of TA endoleaks. There was no difference in patency in any scenario. Independent predictors of TA instability were age (+1-year: hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.94-0.99), stent diameter (+1 mm: HR, 0.67; 95% CI, 0.57-0.80), and BESG (HR, 1.8; 95% CI, 1.1-2.9).

CONCLUSIONS

DBs incorporated using BESGs had lower freedom from TA instability, TA endoleak, and TA reintervention compared with SESGs and HSGs. The patency of DBs was not affected by the type of stent construction. The observed performance disadvantage associated with BESGs appears to have largely been driven by iCAST usage.

Preliminary Outcomes of Viabahn Balloon-Expandable Endoprosthesis as Bridging Stent in Renal Arteries During Fenestrated Endovascular Aortic Repair

PURPOSE

To report preliminary outcomes of Viabahn Balloon-Expandable Endoprosthesis (VBX) stent-graft as bridging stent for renal arteries in fenestrated endovascular aneurysm repair (FEVAR).

MATERIALS AND METHODS

Between 2018 and 2019, patients undergoing FEVAR at 3 referral Italian university hospitals were prospectively collected. During the study period, VBX was the first-line choice as bridging stent for renal arteries. Procedural and anatomical data were analyzed, including renal artery (RA) configuration. A dedicated software (3Mensio, Vascular Imaging, Bilthoeven, The Netherlands) was used and RA anatomy classified as follow: upward-oriented in case of any angle >30° above the horizontal or transverse axis perpendicular to the aortic axis, downward-oriented if there was an angle >30° measured below the transverse axis and downward + upward in case of an angle <30° associated with a renal artery angulation >90°. Primary endpoints were technical success, defined as complete deployment of the fenestrated endograft without target vessel (TV) loss, limb stenosis or occlusion and type I or III endoleak, and freedom from target artery instability (TAI), defined by target vessel-related death, occlusion, rupture or reintervention for stenosis, endoleak or disconnection. Secondary endpoints were target artery patency rate and freedom from reinterventions.

RESULTS

A total of 26 elective FEVAR for juxta/pararenal aneurysm (20), thoracoabdominal type II (3) and type IV (3) were included. Fifty-one RA were planned for revascularization. Of these, 32 were downward, 10 horizontal, 6 upward, 4 were downward + upward. Technical success was achieved in 88.5% (23/26) of patients and 94.2% (48/51) of the TVs. One occlusion (2.1%) occurred within 30 days in a patient with previous endovascular aortic repair and suprarenal fixation. During follow-up (median 10 months), there was 1 type IC endoleak after 6 months (2.1%) in a patient with upward plus downward arterial orientation. Freedom from TAI was 96.1% (CI = 0.89 to 1.04) at first month and 92.3% (CI = 0.82 to 1.03) at 6 months. No aneurysm-related mortality and renal insufficiency occurred during follow-up.

CONCLUSION

The use of VBX as bridging stent of RA in FEVAR is safe and feasible. Previous EVAR and tortuosity of RA may be a challenging on target vessel fate.

Effect of celiac axis compression on target vessel-related outcomes during fenestrated-branched endovascular aortic repair

OBJECTIVE

To report the effect of median arcuate ligament (MAL) compression on outcomes and technical aspects of celiac artery (CA) stenting during fenestrated-branched endovascular aneurysm repair for thoracoabdominal aortic aneurysms (TAAA) or pararenal aortic aneurysms.

METHODS

We retrospectively reviewed the clinical and anatomic data on 300 consecutive patients enrolled in a prospective nonrandomized physician-sponsored investigational device exemption study from 2013 to 2018. From this group, 230 patients with CA incorporation by fenestration or directional branch were included. MAL compression was defined by preoperative computed tomography angiogram as a J-hook narrowing of the proximal CA at the level of the ligament; the shift angle between the downward and upward segments within the CA was measured. End points were technical success, rates of intraoperative or early (30-days) CA branch revision, and freedom from target vessel instability, defined by any death or rupture owing to target vessel complication, occlusion, or reintervention for stenosis, endoleak, or disconnection.

RESULTS

CA incorporation was performed using fenestrations in 118 patients (51%) and directional branches in 112 (49%). MAL compression was present in 97 patients (42%), resulting in a stenosis of more than 50% in 48 (49%). MAL compression was more often present in patients with extent I to III TAAAs compared with extent IV TAAA-pararenal aortic aneurysms (56% vs 31%; P < .001). Technical success rate was 99%. Patients with MAL compression more often received a directional branch (65% vs 37%; P < .001), self-expanding bridging stent grafts (32% vs 16%; P = .007), adjunctive bare metal stents (46% vs 24%; P = .001), and coverage of the gastric artery (44% vs 22%; P < .001). An intraoperative (n = 6, 2.6%) or early (n = 1, 0.4%) revision of the CA branch was required in seven patients (3%) owing to dissection/occlusion (n = 2 [0.9%]), kinking/stenosis (n = 3 [1.3%]), stent dislodgement (n = 1 [0.4%]), or type IC endoleak (n = 1 [0.4%]). A shift angle of less than 120° was the most significant factor associated with CA branch revision (odds ratio, 10.9; 95% confidence interval, 2.3-88.9; P = .013). Freedom from CA branch instability was 97 ± 2% at 4 years, and this outcome was not associated with MAL compression (hazard ratio, 0.83; 95% confidence interval, 0.14-5.02; P = .588) or any other predictor.

CONCLUSIONS

MAL compression was more common in extent I to III TAAAs, and related to additional challenges for CA stenting in fenestrated-branched endovascular aneurysm repair. This process may include bare metal stenting, gastric artery coverage, or early revision, especially in presence of an angulation of less than 120°. However, durable results can be achieved for CA incorporation despite these difficulties.

Endovascular Treatment of Complex Aneurysms with the Use of Covera Stent Grafts

PURPOSE

To characterize the short-term results of a newly available self-expanding covered stent (Covera; CR Bard Peripheral Vascular Inc., Murray Hill, New Jersey) for the reconstruction of target vessels in complex aneurysms.

MATERIALS AND METHODS

From August 2017 to November 2018, this self-expanding covered stent was used in 17 patients (mean 72.6 ± 7.6 years of age) during endovascular aneurysm repair (EVAR) with hypogastric preservation (11.8%), branched EVAR (29.4%), fenestrated (F)-EVAR (17.6%), chimney + F-EVAR (11.8%), or chimney EVAR (29.4%). In more than 48 stented arteries (2.8 ± 1.1/patient), 25 were preserved using this self-expanding covered stent.

RESULTS

All target vessels were successfully preserved. There was no 30-day mortality and 1 in-hospital death. Intraoperative aneurysm exclusion was successful in 14 patients (82.4%) with a perioperative technical success rate of 82.4%. The actuarial survival rate was 93.8% at 6 months and 85.9% at 12 months. Aneurysm sac regression of >5 mm was observed in 4 cases (23.5%), and the sac remained stable in the remaining patients (13 cases [76.5%]). At 12 months, the primary clinical success rate was 76.5%, and assisted primary clinical success rate was 82.4%. No type 3 endoleak was related to a disruption of the reconstruction with the self-expanding covered stent.

CONCLUSIONS

This new self-expanding covered stent provides good short-term patency in chimneys, branches, or fenestrations. Larger series with long-term follow-up are required to determine if the stent can sustain the mechanical stress to which it will be submitted in these repairs.

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.

Preliminary Outcomes of the LifeStream Balloon-Expandable Covered Stent in Fenestrated and Branched Thoracoabdominal Endovascular Repairs

PURPOSE

To evaluate the 1-year outcomes of thoracoabdominal aortic aneurysm (TAAA) repair using fenestrated and branched stent-grafts and a novel balloon-expandable covered stent.

METHODS

Between March 2015 and January 2017, 18 patients (median age 74.7 years; 14 men) received 43 LifeStream balloon-expandable covered stents in conjunction with Zenith fenestrated/branched stent-grafts to bridge 11 celiac trunks, 8 superior mesenteric arteries, and 24 renal arteries (total 32 fenestrations and 11 branches).

RESULTS

Stent delivery and deployment was successful in all cases. At 30 days, 5 patients presented with perifenestration endoleaks (type IIIc) secondary to inadequate sealing of the LifeStream covered stent in 7 (22%) of 32 fenestrations. No type IIIc endoleaks were reported in the branched cases. Four patients had a secondary endovascular reintervention with proximal relining by means of a bare balloon-expandable stent at the perifenestration transition area, with complete resolution of the endoleak at 1-year follow-up. One patient refused reintervention. The last 4 fenestrated stent-grafts of this series had prophylactic perifenestration bare stent relining with no evidence of type IIIc endoleaks at imaging. At a median follow-up of 14.1 months (interquartile range 11, 22), the 12-month LifeStream patency rate was 100%.

CONCLUSION

This single-center preliminary experience with the LifeStream balloon-expandable covered stent in fenestrated/branched stent-grafts for TAAA repairs demonstrated good patency; however, an unexpectedly high rate of type IIIc endoleaks was observed. These endoleaks were resolved with reintervention or during the index procedure by proximal relining with a bare balloon-expandable stent, achieving adequate perifenestration sealing.

Hemodynamic and Anatomic Predictors of Renovisceral Stent-Graft Occlusion Following Chimney Endovascular Repair of Juxtarenal Aortic Aneurysms

PURPOSE

To identify anatomic and hemodynamic changes associated with impending visceral chimney stent-graft occlusion after endovascular aneurysm repair (EVAR) with the chimney technique (chEVAR).

METHODS

A retrospective evaluation was performed of computed tomography scans from 41 patients who underwent juxtarenal chEVAR from 2008 to 2012 to identify stent-grafts demonstrating conformational changes following initial placement. Six subjects (mean age 74 years; 3 men) were selected for detailed reconstruction and computational hemodynamic analysis; 4 had at least 1 occluded chimney stent-graft. This subset of repairs was systematically analyzed to define the anatomic and hemodynamic impact of these changes and identify signature patterns associated with impending renovisceral stent-graft occlusion. Spatial and temporal analyses of cross-sectional area, centerline angle, intraluminal pressure, and wall shear stress (WSS) were performed within the superior mesenteric and renal artery chimney grafts used for repair.

RESULTS

Conformational changes in the chimney stent-grafts and associated perturbations, in both local WSS and pressure, were responsible for the 5 occlusions in the 13 stented branches. Anatomic and hemodynamic signatures leading to occlusion were identified within 1 month postoperatively, with a lumen area <14 mm² (p=0.04), systolic pressure gradient >25 Pa/mm (p=0.03), and systolic WSS >45 Pa (p=0.03) associated with future chimney stent-graft occlusion.

CONCLUSION

Chimney stent-grafts at increased risk for occlusion demonstrated anatomic and hemodynamic signatures within 1 month of juxtarenal chEVAR. Analysis of these parameters in the early postoperative period may be useful for identifying and remediating these high-risk stent-grafts.

Dynamic Geometric Analysis of the Renal Arteries and Aorta following Complex Endovascular Aneurysm Repair

BACKGROUND

Aneurysm regression and target vessel patency during early and mid-term follow-up may be related to the effect of stent-graft configuration on the anatomy. We quantified geometry and remodeling of the renal arteries and aneurysm following fenestrated (F-) or snorkel/chimney (Sn-) endovascular aneurysm repair (EVAR).

METHODS

Twenty-nine patients (mean age, 76.8 ± 7.8 years) treated with F- or Sn-EVAR underwent computed tomography angiography at preop, postop, and follow-up. Three-dimensional geometric models of the aorta and renal arteries were constructed. Renal branch angle was defined relative to the plane orthogonal to the aorta. End-stent angle was defined as the angulation between the stent and native distal artery. Aortic volumes were computed for the whole aorta, lumen, and their difference (excluded lumen). Renal patency, reintervention, early mortality, postoperative renal impairment, and endoleak were reviewed.

RESULTS

From preop to postop, F-renal branches angled upward, Sn-renal branches angled downward (P < 0.05), and Sn-renals exhibited increased end-stent angulation (12 ± 15°, P < 0.05). From postop to follow-up, branch angles did not change for either F- or Sn-renals, whereas F-renals exhibited increased end-stent angulation (5 ± 10°, P < 0.05). From preop to postop, whole aortic and excluded lumen volumes increased by 5 ± 14% and 74 ± 81%, whereas lumen volume decreased (39 ± 27%, P < 0.05). From postop to follow-up, whole aortic and excluded lumen volumes decreased similarly (P < 0.05), leaving the lumen volume unchanged. At median follow-up of 764 days (range, 7-1,653), primary renal stent patency was 94.1% and renal impairment occurred in 2 patients (6.7%).

CONCLUSIONS

Although F- and Sn-EVAR resulted in significant, and opposite, changes to renal branch angle, only Sn-EVAR resulted in significant end-stent angulation increase. Longitudinal geometric analysis suggests that these anatomic alterations are primarily generated early as a consequence of the procedure itself and, although persistent, they show no evidence of continued significant change during the subsequent postoperative follow-up period.

Prospective, nonrandomized study to evaluate endovascular repair of pararenal and thoracoabdominal aortic aneurysms using fenestrated-branched endografts based on supraceliac sealing zones

PURPOSE

To investigate outcomes of manufactured fenestrated and branched endovascular aortic repair (F-BEVAR) endografts based on supraceliac sealing zones to treat pararenal aortic aneurysms and thoracoabdominal aortic aneurysms (TAAAs).

METHODS

A total of 127 patients (91 male; mean age, 75 ± 10 years old) were enrolled in a prospective, nonrandomized single-center study using manufactured F-BEVAR (November 2013-March 2015). Stent design was based on supraceliac sealing zone in all patients with ≥ four vessels in 111 (89%). Follow-up included clinical examination, laboratory studies, duplex ultrasound, and computed tomography imaging at discharge, 1 month, 6 months, and yearly. End points adjudicated by independent clinical event committee included mortality, major adverse events (any mortality, myocardial infarction, stroke, paraplegia, acute kidney injury, respiratory failure, bowel ischemia, blood loss >1 L), freedom from reintervention, and branch-related instability (occlusion, stenosis, endoleak or disconnection requiring reintervention), target vessel patency, sac aneurysm enlargement, and aneurysm rupture.

RESULTS

There were 47 pararenal, 42 type IV, and 38 type I-III TAAAs with mean diameter of 59 ± 17 mm. A total of 496 renal-mesenteric arteries were incorporated by 352 fenestrations, 125 directional branches, and 19 celiac scallops, with a mean of 3.9 ± 0.5 vessels per patient. Technical success of target vessel incorporation was 99.6% (n = 493/496). There were no 30-day or in-hospital deaths, dialysis, ruptures or conversions to open surgical repair. Major adverse events occurred in 27 patients (21%). Paraplegia occurred in two patients (one type IV, one type II TAAAs). Follow-up was >30 days in all patients, >6 months in 79, and >12 months in 34. No patients were lost to follow-up. After a mean follow-up of 9.2 ± 7 months, 23 patients (18%) had reinterventions (15 aortic, 8 nonaortic), 4 renal artery stents were occluded, five patients had type Ia or III endoleaks, and none had aneurysm sac enlargement. Primary and secondary target vessel patency was 96% ± 1% and 98% ± 0.7% at 1 year. Freedom from any branch instability and any reintervention was 93% ± 2% and 93% ± 2% at 1 year, respectively. Patient survival was 96% ± 2% at 1 year for the entire cohort.

CONCLUSIONS

Endovascular repair of pararenal aortic aneurysms and TAAAs, using manufactured F-BEVAR with supraceliac sealing zones, is safe and efficacious. Long-term follow-up is needed to assess the impact of four-vessel designs on device-related complications and progression of aortic disease.