The Role of 3D Printing in the Treatment of Urgent Complex Aortic Pathologies

During a session on Thursday, June 9, dedicated to endovascular aortic repair for acute aortic syndromes, Daniela Branzan, MD, of University Hospital in Leipzig, Germany, described her work in 3D printing of custom-made stent grafts (CMDs) to treat urgent complex aortic pathologies.

We spoke with Dr. Branzan to find out about this cutting-edge work, and how it may help revolutionize the way in which grafts are tailored to patients with minimal delay.

In which patients are off-the-shelf devices likely to be unsuitable, and therefore good candidates for CMDs?

Patients presenting with symptomatic aortic pathologies require urgent treatment regardless of their location. When the visceral aorta and its branches are involved, thus compromising the sealing zone, fenestrated/branched endovascular aneurysm repair (EVAR) are indicated in high-surgical-risk patients. Due to the 15-week time delay for device manufacture, CMDs are not suitable for treating urgent aortic pathologies such as symptomatic or contained rupture of pararenal and thoracoabdominal aortic aneurysms.

Off-the-shelf fenestrated and branched stent grafts are not always available and have anatomical limitations. Alternatively, parallel techniques could be implemented, but the risk of Type Ia endoleak, which is difficult to treat and could be fatal if the aorta ruptures, is as high. Thus, on-site physician modification of endovascular stent grafts for branch vessel preservation is an alternative treatment strategy for acute aortic pathologies localized in the pararenal and thoracoabdominal aorta.

Can you tell us more about the challenges in using fenestrated stent grafts instead?

Endovascular repair using fenestrated stent grafts requires complex planning which results indeed in increased total manufacturing time. Besides that, the stent graft planning is usually based on the centerline of aortic flow, which does not account for the interaction between stent graft and angulated aorta, potentially modifying the alignment between fenestrations and ostia of visceral vessels, leading to questionable accuracy of placement of visceral openings on the custom endograft.

Can you provide a short summary of the key steps involved in preparing 3D-printed grafts, and highlight any particularly important considerations?

We use a commercially available 3D printer to fabricate the 3D aortic models (3DAM). We upload the patient's computed tomography angiography images in a compatible software and we perform a 3D reconstruction the aorta. For the production of the 3DAM we use biocompatible dental resin, which has the advantage of being sterilizable, transparent, and smooth, so that the rotation of the stent graft in the model does not damage it.

We plan the inner diameter of the model to correspond to the diameter of the aorta and replace the renovisceral branches by holes in the 3DAM. After 3D printing, we clean the 3DAM and we steam sterilize it. This entire process takes about seven hours. For creating the fenestrated graft, on a sterile table, we release the stent graft from its sheath inside the sterilized 3DAM, and we rotate and move it in the longitudinal axis until the fenestrations come to lie in wire-free areas of the stent graft.

Once the optimal position of all fenestrations is reached, we mark the positions of fenestrations on the stent graft with a sterile pen. Then we cut the fenestrations into the stent graft using a pointed scalpel and we simultaneously reinforced and radiolabel them by sewing in the radiopaque tip of a guide wire. In the next step, we place single sutures (so-called diameter-reducing ties) along the entire length of the prosthesis, through which an additional guidewire inserted into the sheath system is passed, thus achieving a reversible diameter reduction and better manoeuvrability of the stent graft after release of the prosthesis from the sheath system in the patient's aorta.

Finally, we reinsert the stent graft into the original sheath system and we implant it using the usual technique.

As of June 2022, what results have you been seeing using 3DAM? Do you have study data to share?

We have demonstrated in our patients’ cohort that physician-made stent grafts (PMSGs) for the urgent treatment of pararenal and thoracoabdominal aortic aneurysms in high-risk patients, who are not suitable for commercially available stent grafts, is feasible and safe. Additionally, 3D printing technology can improve the urgent design of patient-specific devices to treat complex aortic pathologies and improve outcomes.

Thus, according to our results and experience, operator independent PMSG planning could be performed, an optimal interventional strategy could be developed after careful examination of 3DAM, and difficulties that might arise during the endovascular repair could be anticipated.

Have you met any challenges or limitations thus far, and if so, how do you plan to overcome them?

The present 3DAM cannot completely mimic aortic behavior due to its rigidity. With further development of 3D printing technology, less rigid biocompatible materials will be available and 3DAM manufacturing time will decrease, thus more patients might benefit from this technology.

What’s next for the technology and any clinical study?

Our goal of using 3DAM for PMSG fabrication was to simplify and standardize PMSG planning for this very difficult patient population. The possibility to have the planning and 3D printing of aortic models performed by qualified non-medical staff could make this treatment option more accessible to daily practice. Whether the fabrication of the PMSG using 3DAM can also increase the accuracy of the position of the manufactured fenestrations, and thus reduce the rate of complications and reinterventions, needs to be investigated in future prospective randomized controlled trials.

Do you have a final ‘take-home’ message?

Good results in a difficult-to-treat patient population can be achieved through proper planning of the procedure with special 3D technology, good patient selection and an interdisciplinary team approach.