ENDOVASCULAR THERMAL SEPTOTOMY FOR CHRONIC POST-DISSECTION AORTIC ANEURYSM

Aidin Baghbani-Oskouei, MD, and Gustavo S. Oderich, MD, from the University of Texas Health Science Center at Houston, Texas, detail the endovascular thermal septotomy technique for chronic post-dissection thoracoabdominal aortic aneurysms (TAAAs), which is set to feature as a video presentation at the end of the William J. von Liebig Forum today (9:15–9:24 a.m.).

patients into either “slow” or “fast” cohorts based upon the progression of their aneurysm.

Chandrashekar will report that integrating the lumen and outer wall structure as unique components within the 3D statistical shape model captured the lumen-thrombus interface, marking this as superior to max diameter, undulation index and radius of curvature in the prediction of AAA growth phenotype, with a p-value of <0.001.

“We can take a CT image, isolate the aneurysm section, extract out the aneurysm shape and extract measurements from the defined shape to a level that is clinically acceptable, and we can do this automatically,” says Chandrashekar of the top line messages of the research.

“Secondly, we are able to improve on already published

“We can take a CT image, isolate the aneurysm section, extract out the aneurysm shape and extract measurements from the defined shape to a level that is clinically acceptable, and we can do this automatically” metrics to predict aneursymal growth, by incorporating not only the aneurysmal sac, but also how the flow lumen interacts with the surrounding thrombus and the surrounding aneurysmal wall,” he adds, commenting that this is “extremely novel in itself.”

Further work has been conducted to validate the model in an independent cohort of patients, which “excitingly,” according to Chandrashekar, shows that the growth model still holds to be predictive.

“Going on from there the next step is to try to establish a prospective study, a longitudinal study following aneurysm patients over time, extracting out additional clinical metrics, for example blood pressure, medication regimen and all those metrics that you would obtain in a randomized controlled study, to see whether this model truly is effective.”

Senior author Regent Lee told VS@VAM: “I congratulate Dr. Chandrashekar in spearheading this international collaborative project and for delivering refinement of our AAA growth prediction model as an independent postdoctoral researcher.”

“The results presented here further highlight the concept of CT image-derived indices as ‘standalone’ biomarkers to predict AAA growth. With appropriate regulatory approvals, this can be further field validated at scale by utilizing existing data already stored in the clinical picture archiving and communication systems (PACS) archives. We look forward to hearing from colleagues who are interested to participate in such collaborative studies.”

AORTIC DISSECTION OFTEN results in chronic aneurysmal degeneration due to progressive false lumen expansion. Thoracic endovascular aneurysm repair (TEVAR) and other techniques of vessel incorporation—such as fenestrated-branched or parallel grafts—have been increasingly utilized to treat chronic post-dissection aneurysms. Even in patients with severe true lumen compression, or when vessels originate from the false lumen, this poses technical difficulties.

In these cases, the limited space from a compressed true lumen may result in inadequate stent-graft expansion or restrict the ability to reposition the device or manipulate catheters. Reentrance techniques may be used selectively to assist with target vessel catheterization. Thermal electrocautery septotomy is a novel technique that has evolved from the cardiology experience with trans-septal or trans-catheter aortic valve procedures. This technique has been applied in select cases to facilitate the creation of proximal and distal landing zones, to disrupt the septum in patients with an excessively compressed true lumen or with vessels that have separate origins from true and false lumens.

At VAM, we present a video that details the technical pitfalls of thermal electrocautery septotomy in a patient with chronic post-dissection aortic aneurysm. The patient presented with isolated enlargement of the iliac artery and modest enlargement of the descending thoracic aorta (3.8 cm). To decrease the risk of spinal cord injury, we recommended endovascular repair of the infrarenal aortic enlargement with left internal iliac preservation using iliac branch endoprosthesis (IBE). The septotomy procedure was used as an adjunct technique to create a suitable proximal landing zone in the infra-renal aorta.

The procedure requires a standard percutaneous approach using perclose technique. Access is established into the true and false lumen and confirmed with intra-vascular ultrasound (IVUS). A 6F Oscor steerable guiding sheath is positioned in the intended area of septotomy, which due to excessive angulation was at the level of the celiac axis (CA). A 35-mm Amplatz Goose Neck Snare kit is advanced via the ipsilateral approach into the false lumen and opened opposite to the steerable sheath to facilitate orientation during guidewire crossing of the dissection septum. The orientation between the steerable sheath and snare is confirmed under fluoroscopy in the anteroposterior, lateral, and oblique views. Once the orientation is optimized, a 0.018 NaviCross catheter and 0.018 Astato hydrophilic guidewire are prepared by removing the guidewire coating and connecting the guidewire to the electrocautery. With the electrocautery set on cut mode at 80 Watts, the guidewire is gently advanced across the dissection membrane without difficulty and promptly snared. The through-and-through guidewire is retracted along with the NaviCross catheter to allow the creation of a 5mm trapeze-shaped area which is denuded from the coating and readvanced into position.

A second 0.018 NaviCross catheter is advanced via the other end of the 0.018 Astato guidewire to protect structures from thermal injury, allowing only the 5-mm trapeze segment to be exposed. The Astato guidewire is again reconnected to the electrocautery and septotomy is performed extending to the distal end of the septum membrane in the external iliac artery. The septotomy is guided by fluoroscopy and confirmed with IVUS. Once the septotomy was completed, the infrarenal EVAR was performed in standard fashion using Gore Excluder Conformable with bilateral iliac limb extensions and a left Gore IBE device. This adjunctive technique is useful to facilitate endovascular repair in patients with subacute or post-dissection aneurysms but has not been used in the acute setting where the friable membrane may be more prone to disrupt or detach from the aortic wall.