Midterm Outcomes for Endovascular Repair of Thoraco-Abdominal Aortic Aneurysms

Objective: To investigate technical and clinical outcomes in patients with thoraco-abdominal aortic aneurysms treated with the multibranched off the shelf Zenith t-Branch stent graft or a custom made device (CMD). Methods: A retrospective study was conducted of patients operated on at a single tertiary vascular centre in Norway. Twenty eight t-Branch and 17 CMD patients were identified. Demographic, aneurysm, and peri-operative data were summarised and compared. Results: Thirty day mortality was 4% (2/45), with mortality rates of 7% (2/28) and 0 in t-Branch and CMD patients, respectively (p = .52). Technical success was 87% (39/45), with a non-significant difference between t-Branch and CMD procedures of 89% (25/28) and 82% (14/17), respectively (p = .63). Stent graft coverage was significantly longer in t-Branch patients (p = .020). Paraparesis or paraplegia developed in 18% (5/28) of t-Branch patients and 12% (2/17) of CMD patients (p = .69), and spinal cord ischaemia was associated with Crawford type II aneurysms (p = .010) and aortic coverage >400 mm (p = .050). The estimated survival at one and two years for t-Branch patients was 93% and 88%, and 100% and 92% for CMD patients. Freedom from re-intervention was estimated at 70% and 43% at one and two years for t-Branch patients, and 58% and 50% for CMD patients. Conclusion: The study showed low 30 day mortality rates, acceptable technical success rates, high medium term survival, and no statistically significant differences in clinically relevant outcomes between t-Branch and CMD patients.publishedVersio

A Steerable and Electromagnetically Tracked Catheter: Navigation Performance Compared With Image Fusion in a Swine Model

Purpose: Cannulation of visceral vessels is necessary during fenestrated and branched endovascular aortic repair. In an attempt to reduce the associated radiation and contrast dose, an electromagnetically (EM) trackable and manually steerable catheter has been developed. The purpose of this preclinical swine study was to evaluate the cannulation performance and compare the cannulation performance using either EM tracking or image fusion as navigation tools. Materials and Methods: Both renal arteries, the superior mesenteric artery, and the celiac trunk were attempted to be cannulated using a 7F steerable, EM trackable catheter in 3 pigs. Seven operators attempted cannulation using first 3-dimensional (3D) image navigation with EM tracking and then conventional image fusion guidance. The rate of successful cannulation was recorded, as well as procedure time and radiation exposure. Due to the lack of an EM trackable guidewire, cannulations that required more than 1 attempt were attempted only with image fusion. The EM tracking position data were registered to preoperative 3D images using a vessel-based registration algorithm. Results: A total of 72 cannulations were attempted with both methods, and 79% (57) were successful on the first attempt for both techniques. There was no difference in cannulation rate (p=1), and time-use was similar. Successful cannulation with image fusion was achieved in 97% of cases when multiple attempts were allowed. Conclusion: This study demonstrated the feasibility of a steerable and EM trackable catheter with 3D image navigation. Navigation performance with EM tracking was similar to image fusion, without statistically significant differences in cannulation rates and procedure times. Further studies are needed to demonstrate this utility in patients with aortic disease.publishedVersio

Prediction of guidewire-induced aortic deformations during EVAR: a finite element and in vitro study

Introduction and aims: During an Endovascular Aneurysm Repair (EVAR) procedure a stiff guidewire is inserted from the iliac arteries. This induces significant deformations on the vasculature, thus, affecting the pre-operative planning, and the accuracy of image fusion. The aim of the present work is to predict the guidewire induced deformations using a finite element approach validated through experiments with patient-specific additive manufactured models. The numerical approach herein developed could improve the pre-operative planning and the intra-operative navigation. Material and methods: The physical models used for the experiments in the hybrid operating room, were manufactured from the segmentations of pre-operative Computed Tomography (CT) angiographies. The finite element analyses (FEA) were performed with LS-DYNA Explicit. The material properties used in finite element analyses were obtained by uniaxial tensile tests. The experimental deformed configurations of the aorta were compared to those obtained from FEA. Three models, obtained from Computed Tomography acquisitions, were investigated in the present work: A) without intraluminal thrombus (ILT), B) with ILT, C) with ILT and calcifications. Results and discussion: A good agreement was found between the experimental and the computational studies. The average error between the final in vitro vs. in silico aortic configurations, i.e., when the guidewire is fully inserted, are equal to 1.17, 1.22 and 1.40 mm, respectively, for Models A, B and C. The increasing trend in values of deformations from Model A to Model C was noticed both experimentally and numerically. The presented validated computational approach in combination with a tracking technology of the endovascular devices may be used to obtain the intra-operative configuration of the vessels and devices prior to the procedure, thus limiting the radiation exposure and the contrast agent dose.publishedVersio

Navigation Technology in Endovascular Aortic Repair

A number of diseases can affect the aorta, and endovascular (minimally invasive) techniques can be used to treat many of these conditions. During endovascular aortic repair, different instruments, such as catheters (plastic tubes), metal wires and balloons are visualized by X-rays. Intermittent aortic injections of contrast medium improve the depiction of the aorta; however, contrast medium may damage kidney function in some patients, radiation can be harmful and X-ray images are 2- dimensional, i.e., the impression of depth is missing. To reduce the use of X-rays and contrast medium, as well as to provide physicians with a better spatial understanding of a patient's vascular anatomy, one can use a navigation system with 3-dimensional images. The use of 3-dimensional visualization and navigation during the endovascular repair of aortic diseases is a subject of research at the Norwegian University of Science and Technology (NTNU), SINTEF Dept. of Medical Technology and St. Olav's Hospital. A navigation system for blood vessels has similarities to the GPS systems used in cars. Such a navigation system can provide the position of different instruments in a 3-dimensional image of a patient’s vascular system without using X-rays and contrast medium. The use of a navigation system may improve precision and simplify future minimally invasive treatment of the aorta. The purpose of this thesis was to investigate the applicability of a navigation system with 3-dimensional images of the vascular system for guidance in endovascular aortic treatment, and to assess the reliability of such a navigation system. The assessment was conducted in four sub-studies. First, we used the navigation system to insert an endoprosthesis (artificial blood vessel) into a model of the abdominal aorta. With specially developed software, the navigation system can use 3-dimensional images (CT scans) of the patient acquired before the procedure as a roadmap. In phantom and animal experiments, the navigation system specified the position of instruments with a high degree of accuracy. Finally, we used the navigation system during the insertion of aortic endoprostheses in patients. In this thesis, we demonstrate that a navigation system that enables visualization of instruments in a 3-dimensional image can be a useful tool during minimally invasive treatment of the aorta. The navigation system is accurate and easy to use

Manually steerable catheter with improved agility

Purpose: A prototype steerable catheter was designed for endovascular procedures. This technical pilot study reports the initial experience using the catheter for cannulation of visceral arteries. Technique: The 7F catheter was manually steerable with operator control handle for bending and rotation of the tip. The maximum bending angle was approximately 90° and full 360° rotation of the tip was supported. The study involved 1 pig with 4 designated target arteries: the left and right renal arteries, the superior mesenteric artery, and the celiac trunk. Fluoroscopy with 3-dimensional (3D) overlay showing the ostia from preoperative computed tomography angiography was used for image guidance. The cannulation was considered successful if the guidewire was placed well inside the target artery. In addition to evaluating cannulation success, procedure time and associated radiation doses were recorded. The procedure was performed twice with 2 different operators. Conclusions: Both operators successfully reached all 4 target arteries, demonstrating the feasibility of the steerable catheter for endovascular cannulation of visceral arteries. No contrast medium was used, and median radiation dose was 4.5 mGy per cannulation. An average of approximately 2 minutes was used per cannulation. This study motivates further testing in a more comprehensive study to evaluate reproducibility in several animals and with inclusion of more operators. Further development by integrating the new catheter tool in a navigation system is also an interesting next step, combining fine control of catheter tip movements and 3D image guidance without ionizing radiation

Manually Steerable Catheter With Improved Agility

Purpose: A prototype steerable catheter was designed for endovascular procedures. This technical pilot study reports the initial experience using the catheter for cannulation of visceral arteries. Technique: The 7F catheter was manually steerable with operator control handle for bending and rotation of the tip. The maximum bending angle was approximately 90° and full 360° rotation of the tip was supported. The study involved 1 pig with 4 designated target arteries: the left and right renal arteries, the superior mesenteric artery, and the celiac trunk. Fluoroscopy with 3-dimensional (3D) overlay showing the ostia from preoperative computed tomography angiography was used for image guidance. The cannulation was considered successful if the guidewire was placed well inside the target artery. In addition to evaluating cannulation success, procedure time and associated radiation doses were recorded. The procedure was performed twice with 2 different operators. Conclusions: Both operators successfully reached all 4 target arteries, demonstrating the feasibility of the steerable catheter for endovascular cannulation of visceral arteries. No contrast medium was used, and median radiation dose was 4.5 mGy per cannulation. An average of approximately 2 minutes was used per cannulation. This study motivates further testing in a more comprehensive study to evaluate reproducibility in several animals and with inclusion of more operators. Further development by integrating the new catheter tool in a navigation system is also an interesting next step, combining fine control of catheter tip movements and 3D image guidance without ionizing radiation