Endovascular aneurysm repair (EVAR) has transformed the treatment of abdominal aortic aneurysms by offering many patients a less invasive alternative to open surgery. But EVAR also leaves behind a problem that has never been fully solved: the aneurysm sac remains in place.
In many patients, that sac never shrinks. In some, it grows, raising concern about future rupture risk. Physicians have therefore been left monitoring, rescanning, and, when necessary, reintervening.
Shape Memory Medical’s AAA-SHAPE Pivotal Trial, which completed enrollment on July 7, 2026, is the first randomized controlled pivotal trial to directly test whether proactive aneurysm sac embolization at the time of EVAR can change that pattern. The trial randomized 180 patients 2:1 across 48 centers in the United States, Europe, and New Zealand, with follow-up planned through five years. Primary endpoints include 30-day safety and the proportion of patients achieving at least 10% aneurysm sac volume reduction without AAA-related reintervention at one year.
Ted Ruppel, President and CEO of Shape Memory Medical, has led the company’s development of its shape memory polymer embolization platform across peripheral and aortic applications. Mary Dennehy, Vice President of Marketing, spent years at Endologix working in endovascular aneurysm repair before joining Shape Memory Medical. Together, they explain why sac non-regression matters, why the aortic indication requires its own clinical evidence, and what the AAA-SHAPE trial is designed to show.
VP of Marketing, Shape Memory Medical
Moe: How did your time at Endologix shape your view of what EVAR leaves unsolved?
Mary Dennehy: I spent a number of years at Endologix focused on endovascular therapies for abdominal aortic aneurysms. During that time, I saw how transformative EVAR can be for patients. It is a much less invasive option than open surgery, and for patients who are appropriate candidates, it has changed the practice of aortic therapy.
But I also saw how much unfinished business can remain after the EVAR stent graft is in place. The device excludes the aneurysm from the blood flow and pressure that can cause it to grow and potentially rupture. The limitation is that the aneurysm sac itself is still there.
For many patients, that sac never shrinks. It may remain stable, some patients develop endoleaks, and some go on to experience further aneurysm growth even when the initial procedure appeared technically successful.
Physicians are often left watching the sac over time and hoping it will regress. If it does not, the options are limited, inconsistent, and usually reactive. That experience shaped my view that sac behavior after EVAR is not just a radiographic detail. It is central to the durability of the repair. When I learned what Shape Memory Medical was doing, it felt like an opportunity to continue that work in a very meaningful way.
“Physicians are often left watching the sac over time and hoping it will regress. If it does not, the options are limited, inconsistent, and usually reactive.”
Moe: Why does sac non-regression resonate so strongly when you talk to physicians about this trial?
Mary Dennehy: The consequence that seems to land hardest is the recognition that a sac that does not regress is not necessarily a benign finding. For many physicians, sac non-regression represents uncertainty. It means continued surveillance, additional CT imaging with radiation exposure, and the potential for rehospitalization or secondary procedures, each of which carries its own risks.
Patient anxiety may also persist after EVAR. Although the aneurysm has been treated, patients still undergo ongoing imaging surveillance because the sac remains in place and late complications or reinterventions can occur. When follow-up imaging shows that the sac has not regressed, or that an endoleak persists, the uncertainty can affect how patients perceive the success and durability of their treatment.
A common cause of sac non-regression is Type II endoleak. A type II endoleak occurs when blood continues to flow into the aneurysm sac through small blood vessels arising from the aneurysm sac. Persistent type II endoleaks are part of that story, but the larger issue is sac behavior and what it may signal about long-term outcomes. Some patients have type II endoleaks that prevent the aneurysm from shrinking. Other patients have no visible endoleak, yet the sac still fails to regress. The reasons are multifactorial.
A key distinction is that this is not simply an endoleak treatment strategy. Historically, many interventions after EVAR have been reactive: an endoleak is detected, the sac enlarges, and then physicians decide whether to intervene. The concept behind proactive sac embolization is different. It asks whether filling the sac at the time of EVAR can reduce the risk of persistent flow, support thrombus organization, and promote sac regression before the patient enters that cycle of surveillance and secondary intervention.
For decades, physicians have understood that sac regression after EVAR is associated with better long-term outcomes, but the field has not had a proactive, evidence-based way to influence sac behavior at the time of the initial repair. AAA-SHAPE is designed to answer whether treating the sac up front can change the trajectory of the aneurysm after EVAR, rather than waiting to see which patients develop problems later.
The clinical concern that resonates most with physicians is whether EVAR has delivered the durable protection they want for the patient. When the sac does not shrink, that question remains open.
President & CEO, Shape Memory Medical
Moe: Shape Memory Medical’s technology is already used for peripheral embolization. Why does its use in the aneurysm sac require separate clinical evaluation?
Ted Ruppel: The underlying shape memory polymer technology may be familiar to physicians, but using IMPEDE-FX RapidFill to embolize the aneurysm sac during EVAR is a distinct application. It involves different anatomy, clinical objectives, procedural considerations, and potential risks. IMPEDE-FX RapidFill remains investigational for the aortic indication and is not cleared or approved for that use in the United States.
That is why we conducted AAA-SHAPE: to evaluate this application rigorously in a prospective, randomized trial and determine whether treating the sac at the time of EVAR improves sac regression and other clinically meaningful outcomes.
The randomized design is important because sac behavior after EVAR can be influenced by many factors, including anatomy, thrombus burden, device choice, endoleaks, and patient-specific healing. A randomized trial gives the field a much cleaner way to evaluate whether adjunctive sac embolization itself changes outcomes, rather than relying only on retrospective comparisons or single-arm experience.
What makes this platform interesting for the aneurysm sac is that shape memory polymer was designed to create a stable, porous scaffold for embolization. In the aortic sac, the goal is not simply to drop coils into a space. The goal is to fill a large, irregular volume in a controlled way and create conditions that may support durable sac thrombosis and regression over time.
Another important part of the study is that the device is used during the index EVAR procedure. That matters because physicians are already treating the aneurysm, and the question is whether sac embolization can be incorporated into the EVAR workflow with the goal of improving long-term durability without creating a new treatment episode later.
With AAA-SHAPE, we are seeking high-quality clinical evidence to show whether adjunctive sac management at the time of EVAR can meaningfully improve sac outcomes. Until that evidence is reviewed and the aortic indication is granted, this use remains investigational.
Moe: Why will the endovascular community look at sac volume reduction, specifically, when the results are published?
Mary Dennehy: A lot of thought went into the design of this trial and the data we are collecting. We believe the endovascular community will look at the totality of the data. Sac regression is important, but physicians will also consider the absence of rehospitalization, the absence of reintervention, and other clinical outcomes alongside it.
Sac volume regression, in particular, will be important because it provides a more complete picture of sac behavior. The aneurysm is a three-dimensional structure. Historically, and even today, the standard measurement to assess changes in sac size has been diameter. That is largely because the tools available for measuring aortic sac volume have not always been practical, automated, or easy to use. But with improved software, and increasingly with AI-enabled tools, volume measurement is becoming more feasible. Volume is the more sensitive and complete measure of sac behavior.
That said, the most persuasive result will likely be consistency across endpoints: sac volume reduction, sac diameter reduction, fewer persistent endoleaks, and fewer secondary interventions. If those signals align, it becomes a much stronger clinical story than any single endpoint on its own.
We are also collecting patient quality-of-life data to evaluate whether there is a meaningful difference between patients whose sacs shrink and those whose sacs do not, including differences in anxiety, state of mind, and how they feel about their treatment overall.
“The most persuasive result will likely be consistency across endpoints. If those signals align, it becomes a much stronger clinical story than any single endpoint on its own.”
Moe: How does a successful five-year outcome for study participants actually look different in their lives?
Ted Ruppel: Five years from now, success would mean that these patients have a more durable EVAR result with fewer late-stage problems. Ideally, their aneurysm sacs have regressed, they have avoided repeat procedures, and their physicians have much greater confidence that the aneurysm has stabilized.
For patients, it is about living with more certainty. Many EVAR patients today experience sac stability or expansion rather than shrinkage. Some physicians look at a stable or expanding sac and feel that the procedure did not deliver the outcome they had hoped for. The goal is to treat the aneurysm, but in many ways, EVAR bypasses the aneurysm and then relies on the sac to heal over time. What we are hoping to add is the ability to actively support sac shrinkage and improve long-term outcomes.
If the trial is successful, it could shift the conversation from managing sac failure after EVAR to preventing it at the time of EVAR. That would be a meaningful change for physicians, patients, hospitals, and the healthcare system because the downstream burden of surveillance, uncertainty, secondary intervention, and late aneurysm-related events is substantial.
Ultimately, success would mean fewer follow-up concerns, fewer endoleaks, fewer reinterventions, and more confidence that the initial procedure delivered a durable result.
Ted Ruppel is President and Chief Executive Officer of Shape Memory Medical Inc. Mary Dennehy is Vice President of Marketing at Shape Memory Medical Inc.
Moe Alsumidaie, MBA, MSF, is founder and Chief Editor of Vanguard Publications, which publishes Clinical Trial Vanguard, Pharma Vanguard and BullScope, and Head of Research at CliniBiz. He has two decades in clinical trial operations and data science, with earlier roles at Genentech, Abbott Vascular and Stanford University Medical Center, and is a guest lecturer in clinical trial sciences at Rutgers University.
