Nicholas Cheshire

Treatment of Complex Aneurysmal Disease with Fenestrated and Branched Stent Grafts

OBJECTIVES To describe our experience of treating juxtarenal (JRAAAs <4mm neck) and thoracoabdominal aortic aneurysms (TAAAs) using fenestrated and branched stent graft technology. DESIGN Prospective single centre experience. METHODS Since 2005, 29 fenestrated/branched procedures have been performed. 15 patients are studied with JRAAAs (n=7; median neck length 0mm (IQR 0-3.8)) or TAAAs (type I (n=2), III (n=2), IV (n=4)). ASA grade III in 12/15. Maximum diameter of aneurysm 64 mm (56-74 mm). Aneurysms were excluded using covered stents or branches from the main body to patent visceral vessels (40 target vessels total). Pre-operative and follow-up CT scans (1, 3, and 12 months) were analysed by a single Vascular Interventional Radiologist. RESULTS Technical success for cannulation and stenting of target vessels was 98%. In-hospital mortality was 0%. One patient underwent conversion to open repair. Five had major complications including one paraplegia (type III TAAA) with subsequent recovery. Median length of stay was 9 days (IQR 7-18.75). At a median follow-up of 12 months (9-14), CT confirmed 36/37 (97%) target vessels remain patent. Sac size increased >5 mm in one patient only. There were no type I endoleaks, three type II endoleaks (one embolised, two under surveillance) and three type III endoleaks (two successfully treated percutaneously, one aneurysm ruptured 18 months after endografting and died). CONCLUSION In selected patients, fenestrated and branched stents appear to be a safe and effective alternative to surgery for juxtarenal and thoracoabdominal aneurysms. The complication and mortality rates are low. The long-term durability of this procedure, however, needs to be proven.

Early Results of Fenestrated Endovascular Repair of Juxtarenal Aortic Aneurysms in the United Kingdom

Background— Fenestrated endovascular repair of abdominal aortic aneurysms has been proposed as an alternative to open surgery for juxtarenal and pararenal abdominal aortic aneurysms. At present, the evidence base for this procedure is predominantly limited to single-center or single-operator series. The aim of this study was to present nationwide early results of fenestrated endovascular repair in the United Kingdom. Methods and Results— All patients who underwent fenestrated endovascular repair between January 2007 and December 2010 at experienced institutions in the United Kingdom(>10 procedures) were retrospectively studied by use of the GLOBALSTAR database. Site-reported data relating to patient demographics, aneurysm morphology, procedural details, and outcome were recorded. Data from 318 patients were obtained from 14 centers. Primary procedural success was achieved in 99% (316/318); perioperative mortality was 4.1%, and intraoperative target vessel loss was observed in 5 of 889 target vessels (0.6%). The early reintervention (<30 days) rate was 7% (22/318). There were 11 deaths during follow-up; none were aneurysm-related. Survival by Kaplan–Meier analysis was 94% (SE 0.01), 91% (0.02), and 89% (0.02) at 1, 2, and 3 years, respectively. Freedom from target vessel loss was 93% (0.02), 91% (0.02), and 85% (0.06), and freedom from late secondary intervention (>30 days) was 90% (0.02), 86% (0.03), and 70% (0.08) at 1, 2, and 3 years. Conclusions— In this national sample, fenestrated endovascular repair has been performed with a high degree of technical and clinical success. Late survival and target vessel patency are satisfactory. These results support continued use and evaluation of this technique for juxtarenal aneurysms, but illustrate the need for a more robust evidence base.

Evaluation of robotic endovascular catheters for arch vessel cannulation.

OBJECTIVE Conventional catheter instability and embolization risk limits the adoption of endovascular therapy in patients with challenging arch anatomy. This study investigated whether arch vessel cannulation can be enhanced by a remotely steerable robotic catheter system. METHODS Seventeen clinicians with varying endovascular experience cannulated all arch vessels within two computed tomography-reconstructed pulsatile flow phantoms (bovine type I and type III aortic arches), under fluoroscopic guidance, using conventional and robotic techniques. Quantitative (catheterization times, catheter tip movements, vessel wall hits, catheter deflection) and qualitative metrics (Imperial College Complex Endovascular Cannulation Scoring Tool [IC3ST]) performance scores were compared. RESULTS Robotic catheterization techniques resulted in a significant reduction in median carotid artery cannulation times and the median number of catheter tip movements for all vessels. Vessel wall contact with the aortic arch wall was reduced to a median of zero with robotic catheters. During stiff guidewire exchanges, robotic catheters maintained stability with zero deflection, independent of the distance the catheter was introduced into the carotid vessels. Overall IC3ST performance scores (interquartile range) were significantly improved using the robotic system: Type I arch score was 26/35 (20-30.8) vs 33/35 (31-34; P = .001), and type III arch score was 20.5/35 (16.5-28.5) vs 26.5/35 (23.5-28.8; P = .001). Low- and medium-volume interventionalists demonstrated an improvement in performance with robotic cannulation techniques. The high-volume intervention group did not show statistically significant improvement, but cannulation times, movements, and vessel wall hits were significantly reduced. CONCLUSION Robotic technology has the potential to reduce the time, risk of embolization and catheter dislodgement, radiation exposure, and the manual skill required for carotid and arch vessel cannulation, while improving overall performance scores.

Cognitive training improves clinically relevant outcomes during simulated endovascular procedures

OBJECTIVES Virtual reality (VR) simulation has been suggested to objectively assess endovascular skills. The aim of this study was to determine the impact of cognitive training on technical performance of inexperienced subjects on a commercially available VR simulator (VIST, Vascular Intervention Simulation Trainer, Mentice, Gothenburg, Sweden). METHODS Forty-seven subjects treated an identical virtual iliac artery stenosis endovascularly. Surgical trainees without endovascular experience were allocated to two training protocols: group A(1) (n = 10) received a 45 minute didactic session followed by an expert demonstration of the procedure that included error-based learning, whereas group A(2) (n = 10) was only given a demonstration of an iliac dilation and stent procedure. All trainees performed the intervention immediately following the expert demonstration. Twenty-seven endovascular physicians were recruited (>100 endovascular interventions). Performance was assessed using the quantitative (procedure and fluoroscopy time) and qualitative (stent/vessel ratio and residual stenosis) assessment parameters recorded by the simulator. RESULTS The end-product (qualitative metrics) in the cognitive-skills group A(1) was similar to those of the endovascular physicians, though A(2) performed significantly worse than the physicians (group B): stent/vessel ratio (A(1) 0.89 vs B 0.96, P = .960; A(2) 0.66 vs B 0.96, P = .001) and residual stenosis (A(1) 11 vs B 4%, P = .511; A(2) 35 vs B 4%, P < .001). Group A(1) took longer to perform the procedure (A(1) 982 vs B 441 seconds, P < .001), with greater use of fluoroscopy than group B (A(1) 609 vs B 189 seconds, P < .001) whereas group A(2) performed the intervention as quickly as group B (A(2) 358 vs B 441 seconds, P = .192) but used less fluoroscopy (A(2) 120 vs 189 seconds, P = .002). CONCLUSION Cognitive-skills training significantly improves the quality of end-product on a VR endovascular simulator, and is fundamental prior to assessment of inexperienced subjects.

Experienced Endovascular Interventionalists Objectively Improve their Skills by Attending Carotid Artery Stent Training Courses

OBJECTIVE Carotid artery stenting (CAS) is an advanced endovascular intervention with a steep learning curve. Virtual reality (VR) simulation has been proposed as a means to train and objectively assess technical performance. AIM To objectively assess psychomotor skills acquisition of experienced interventionalists attending a two-day CAS course, using a VR simulator. METHODS Both cognitive and technical skills of 11 interventionalists were trained in a two-day course using didactic sessions, case reviews, supervised VR simulation and live-cases. Pre- and post-course skills were assessed through performance on the same CAS procedure using metrics derived from the simulator. RESULTS Significant differences were noted between pre- and post-course performance for procedure (36 vs. 20min., p=0.005), X-ray (20 vs. 11min., p=0.016) and delivery-retrieval time of the embolic protection device (12 vs. 9min., p=0.007). Advancement of the guiding catheter without a leading wire occurred to a greater extent pre- versus post-course (199 vs. 152mm., p=0.050) as did spasm of the internal carotid artery (4 vs. 2, p=0.049). CONCLUSIONS This study has objectively proven a benefit for experienced interventionalists to attend CAS courses for skills acquisition measured by a VR simulator. These data can be used to offer participants an insight into their skills and objectively audit course efficacy.

Early Results of Endovascular Treatment of the Thoracic Aorta Using the Valiant Endograft

Endovascular repair of the thoracic aorta has been adopted as the first-line therapy for much pathology. Initial results from the early-generation endografts have highlighted the potential of this technique. Newer-generation endografts have now been introduced into clinical practice and careful assessment of their performance should be mandatory. This study describes the initial experience with the Valiant endograft and makes comparisons with similar series documenting previous-generation endografts. Data were retrospectively collected on 180 patients treated with the Valiant endograft at seven European centers between March 2005 and October 2006. The patient cohort consisted of 66 patients with thoracic aneurysms, 22 with thoracoabdominal aneurysms, 19 with an acute aortic syndrome, 52 with aneurysmal degeneration of a chronic dissection, and 21 patients with traumatic aortic transection. The overall 30-day mortality for the series was 7.2%, with a stroke rate of 3.8% and a paraplegia rate of 3.3%. Subgroup analysis demonstrated that mortality differed significantly between different indications; thoracic aneurysms (6.1%), thoracoabdominal aneurysms (27.3%), acute aortic syndrome (10.5%), chronic dissections (1.9%), and acute transections (0%). Adjunctive surgical procedures were required in 63 patients, and 51% of patients had grafts deployed proximal to the left subclavian artery. Comparison with a series of earlier-generation grafts demonstrated a significant increase in complexity of procedure as assessed by graft implantation site, number of grafts and patient comorbidity. The data demonstrate acceptable results for a new-generation endograft in series of patients with diverse thoracic aortic pathology. Comparison of clinical outcomes between different endografts poses considerable challenges due to differing case complexity.

The role of robotic endovascular catheters in fenestrated stent grafting

OBJECTIVE Fenestrated stent grafting has allowed the treatment of complex thoraco-abdominal aneurysm disease via a totally endovascular approach, but the procedure can be technically challenging and time consuming. We investigated whether this procedure may be enhanced by remotely steerable robotic endovascular catheters. METHODS A four-vessel fenestrated stent graft partially deployed within a computed tomography (CT)-reconstructed pulsatile thoraco-abdominal aneurysm silicon model was used. Fifteen operators were recruited to participate in the study and divided into three groups, based on their endovascular experience: group A (n = 4, 100-200 endovascular procedures, group B (n = 5, 200-300), and group C (n = 6, >300). All operators were asked to cannulate the renal and visceral vessels under fluoroscopic guidance, using conventional and robotic techniques. Quantitative (catheterization times and wire/catheter tip movements) and qualitative metrics (procedure-specific-rating scale [IC3ST]), which grades operators on catheter use, instrumentation, successful cannulation/catheterization, and overall performance were compared. RESULTS Median procedure time for cannulation of all four vessels was reduced using the robotic system (2.87 min, interquartile range [IQR; 2.20-3.90] versus 17.24 min [11.90-19.80]; P < .001) for each individual operator, regardless of the level of endovascular experience. The total number of wire/catheter movements taken to complete the task was also significantly reduced (38, IQR [29-57] versus 454 [283-687]; P < .001). There were significant differences in time and movement for cannulation of each individual vessel in the phantom. Robotic catheter operator radiation exposure was negligible as the robotic workstation is remote and away from the radiation source. Overall performance scores significantly improved using the robotic system, despite minimal operator exposure to this technology (IC3ST score 29/35, IQR [22.8-30.7] versus 19/35 [13-24.3]; P = .002). Each group of operators demonstrated an improvement in performance with robotic cannulation. For group A, median IC3ST score was 28/35, IQR (22-33) versus 15/35 (11-20); P = .04; for group B, 30/35 (27-31) versus 19/35 (18-24); P = .07; and for group C, 28.8/35 (28.5-29) versus 22/35 (16-24); P = .06. For groups B and C, these differences did not reach statistical significance. CONCLUSION Robotic catheterization of target vessels during this procedure is feasible and minimizes radiation exposure for the operator. Steerable robotic catheters with intuitive control may overcome some of the limitations of standard catheter technology, enhance target vessel cannulation, reduce instrumentation, and improve overall performance scores.

Local and Global Geometric Influence on Steady Flow in Distal Anastomoses of Peripheral Bypass Grafts

We consider the effect of geometrical configuration on the steady flow field of representative geometries from an in vivo anatomical data set of end-to-side distal anastomoses constructed as part of a peripheral bypass graft. Using a geometrical classification technique, we select the anastomoses of three representative patients according to the angle between the graft and proximal host vessels (GPA) and the planarity of the anastomotic configuration. The geometries considered include two surgically tunneled grafts with shallow GPAs which are relatively planar but have different lumen characteristics, one case exhibiting a local restriction at the perianastomotic graft and proximal host whilst the other case has a relatively uniform cross section. The third case is nonplanar and characterized by a wide GPA resulting from the graft being constructed superficially from an in situ vein. In all three models the same peripheral resistance was imposed at the computational outflows of the distal and proximal host vessels and this condition, combined with the effect of the anastomotic geometry, has been observed to reasonably reproduce the in vivo flow split. By analyzing the flow fields we demonstrate how the local and global geometric characteristics influences the distribution of wall shear stress and the steady transport of fluid particles. Specifically, in vessels that have a global geometric characteristic we observe that the wall shear stress depends on large scale geometrical factors, e.g., the curvature and planarity of blood vessels. In contrast, the wall shear stress distribution and local mixing is significantly influenced by morphology and location of restrictions, particular when there is a shallow GPA. A combination of local and global effects are also possible as demonstrated in our third study of an anastomosis with a larger GPA. These relatively simple observations highlight the need to distinguish between local and global geometric influences for a given reconstruction. We further present the geometrical evolution of the anastomoses over a series of follow-up studies and observe how the lumen progresses towards the faster bulk flow of the velocity in the original geometry. This mechanism is consistent with the luminal changes in recirculation regions that experience low wall shear stress. In the shallow GPA anastomoses the proximal part of the native host vessel occludes or stenoses earlier than in the case with wide GPA. A potential contribution to this behavior is suggested by the stronger mixing that characterizes anastomoses with large GPA.

Robot-assisted Fenestrated Endovascular Aneurysm Repair (FEVAR) Using the Magellan System

A 67-year-old man underwent robot-assisted three-vessel fenestrated endovascular aneurysm repair (FEVAR) for a 7.3-cm juxtarenal aneurysm. The 6-F robotic catheter was manipulated from a remote workstation, away from the radiation source. Robotic cannulation of the left renal artery was achieved within 3 minutes. System setup time was 5 minutes. There were no postoperative complications. Computed tomography angiography performed at discharge and at 4-month follow-up confirmed target vessel patency with no evidence of an endoleak. Selective cannulation of target vessels during FEVAR using this novel technology is feasible. Endovascular robotics may have a role in simplifying complex endovascular tasks and potentially reducing radiation exposure to the operator.

Validation of Video-based Skill Assessment in Carotid Artery Stenting

OBJECTIVES To develop weighted error-based, generic and procedure-specific rating scales, to validate these scales for video-based assessment during virtual carotid artery stent (CAS) procedures and correlate them with simulator-derived metrics. METHODS A questionnaire was developed to assess the technique during live CAS procedures. Errors were rated from 1 (unimportant) to 5 (life-threatening) by 28 highly experienced CAS (>50 CAS) physicians. Virtual CAS procedure was performed by 21 interventionalists with varied CAS experience. Fluoroscopy screen and hand movements were video-taped, and simulator-derived metrics recorded. Experienced CAS practitioners then rated the video-taped performances using weighted error, generic and procedure-specific rating scales. RESULTS Of the 23 errors assessed, 12 were regarded as moderate (score 3), six serious (score 4) and four life-threatening (score 5). The generic rating scale was able to detect significant differences in performance between inexperienced and experienced CAS operators (score 25 vs. 32 respectively, P<0.01). All scoring systems demonstrated good inter-rater reliability (alpha=0.61-0.87). Significant correlations were observed between simulator-derived and video-based scores: weighted error-based score (r: 0.76, P<0.01), generic (r: 0.62, P<0.01) and procedure-specific (r: 0.76, P<0.01) rating scales. CONCLUSIONS The generic endovascular rating scale differentiated between levels of CAS experience among skilled interventionalists and correlated to simulator-based error scoring.