Hélène Héon

Radiofrequency Perforation System for in Vivo Antegrade Fenestration of Aortic Stent-Grafts

Purpose: To evaluate the ability to create in vivo antegrade fenestrations (IVAF) using a radiofrequency probe in juxtarenal aortic stent-grafts to preserve the patency of renal arteries. Methods: Modified stent-grafts with an unsupported fenestration area were deployed in the juxtarenal aorta of 2 25-kg dogs. Prior to deployment, both renal arteries were marked with detachable coils that were later removed (dog 1) or with hydrophilic catheters (dog 2). After deployment, a radiofrequency probe was used to perforate the graft. If puncture was successful, attempts were made to pass guidewires into the renal arteries for balloon dilation and stenting of the graft perforation. Doppler ultrasound scans of the renal arteries were taken after 1 week. Doppler ultrasound and angiography were repeated prior to autopsy and macroscopic analysis at 1 month. Results: Fenestration was attempted in 3 renal arteries (1 in dog 1 and 2 in dog 2). It was successful in 2 renal arteries but required 6 attempts in dog 1 and 3 in dog 2. The failed case was related to the position of a stent-graft strut close to the fenestration area. One stent thrombosis was seen during follow-up, while the other fenestrated artery remained patent. No stent fracture was encountered during follow-up. Conclusion: This radiofrequency device allowed successful fenestration but was difficult to control. Technical improvements are required to improve clinical success and patency.

In Vivo Antegrade Fenestration of Abdominal Aortic Stent-Grafts:

Purpose: To examine in a canine model the feasibility of antegrade fenestration of abdominal aortic stent-grafts to preserve the patency of the renal arteries. Methods: Two large dogs underwent antegrade fenestration of stent-grafts in the perirenal aorta. Before fenestration, bare stents were inserted in both renal arteries as fluoroscopic landmarks. A 12-mm iliac extension served as the canine aortic endograft. The first procedure was done under ultrasound and fluoroscopic guidance, using an intravascular ultrasound (IVUS) probe inserted in the vena cava and a Pioneer IVUS catheter. The second was performed exclusively under fluoroscopic guidance with a Brockenbrough needle. Angiograms and duplex ultrasound were planned for 1 month, after which the dogs would be sacrificed for autopsy. The explanted endograft was subjected to biomaterials analysis, with a focus on fabric tear. Results: Perforation of the aortic graft and catheterization of the renal arteries with a floppy guidewire were possible in both animals. In dog 1, aortic graft dilation and subsequent fenestration were not possible, and the experiment was terminated. However, the procedure was successful in both renal arteries of dog 2. At 1-month follow-up in this dog, both renal arteries were patent. Stent fractures were observed bilaterally. There was no extension of the damage to the fabric beyond the area of fenestration. Conclusion: In vivo antegrade fenestration of aortic endografts is technically feasible. However, improvements in technique, instrumentation, and materials are required to make it a reliable and reproducible way of allowing stent-graft vascularization of aortic side branches.

Implementation of a PCR assay of Pasteurella pneumotropica to accurately screen for contaminated laboratory mice.

The authors implemented a PCR protocol to rapidly screen for Pasteurella pneumotropica and to accurately identify contaminated laboratory mice in a clinical setting. This protocol was implemented in response to a severe outbreak of P. pneumotropica in their animal facility. Although a sentinel program was in place to routinely screen for P. pneumotropica, it was inadequate for the identification of contaminated animals. As a result, several additional strains of mice were contaminated and developed clinical signs of infection. The authors implemented a screening method using PCR with reported primer pairs previously developed to identify the biotype isolates of P. pneumotropica in laboratory mice. Throat culture swabs were collected from live mice and placed in a bacterial culture. The DNA from these cultures was isolated and screened by PCR. This procedure enabled the authors to eliminate P. pneumotropica from several animal housing rooms. The assay can be easily applied in most animal facilities.

Endovascular Repair of Abdominal Aortic Aneurysm: Follow-up with Noninvasive Vascular Elastography in a Canine Model

PURPOSE To assess the ability of noninvasive vascular elastography (NIVE) to help characterize endoleaks and thrombus organization in a canine model of abdominal aortic aneurysm after endovascular aneurysm repair with stent-grafts, in comparison with computed tomography (CT) and pathologic examination findings. MATERIALS AND METHODS All protocols were approved by the Animal Care Committee in accordance with the guidelines of the Canadian Council of Animal Care. Stent-grafts were implanted in a group of 18 dogs with aneurysms created in the abdominal aorta. Type I endoleak was created in four aneurysms; type II endoleak, in 13 aneurysms; and no endoleak, in one aneurysm. Doppler ultrasonography and NIVE examinations were performed at baseline and at 1-week, 1-month, 3-month, and 6-month follow-up. Angiography, CT, and macroscopic tissue examination were performed at sacrifice. Strain values were computed by using the Lagrangian speckle model estimator. Areas of endoleak, solid organized thrombus, and fresh thrombus were identified and segmented by comparing the results of CT and macroscopic tissue examination. Strain values were compared by using the Wilcoxon rank-sum and Kruskal-Wallis tests. RESULTS All stent-grafts were successfully deployed, and endoleaks were clearly depicted in the last follow-up elastography examinations. Maximal axial strains over consecutive heart cycles in endoleak, organized thrombus, and fresh thrombus areas were 0.78% ± 0.22, 0.23% ± 0.02, 0.10% ± 0.04, respectively. Strain values were significantly different between endoleak and organized or fresh thrombus areas (P < .000) and between organized and fresh thrombus areas (P < .0002). No correlation was found between strain values and type of endoleak, sac pressure, endoleak size, and aneurysm size. CONCLUSION NIVE may be able to help characterize endoleak and thrombus organization, regardless of the size, pressure, and type of endoleak.