INTERVIEW

By Bryan Kay

THE FIRST AH-HA MOMENT CAME during a talk at a national meeting being given by one of the foremost vascular surgeons in the U.S. The second came back at home base. The theme common to both? That major vascular operations and complications were being carried out by other specialties engaged in robotics-assisted surgery.

“I was at the Society for Clinical Vascular Surgery one year, and was watching a robotic left renal vein transposition—that’s a very sophisticated operation—by Sam Money, at that time the chief of the Mayo Clinic at Scottsdale,” says Alan Lumsden, MD, the Walter W. Fondren III Presidential Distinguished Chair at Houston Methodist’s DeBakey Heart & Vascular Center in Houston, Texas. “And then he said: ‘I didn’t do this operation, the urologist did it.’”

Then, back home in Houston, Lumsden was called to assist with a bleeding complication during a pelvic procedure being carried out by a gynecologist. When he arrived, the specialist—performing the procedure robotically—asked Lumsden if he could resolve some bleeding from an iliac artery using the robot. His response was in the negative. “I can’t do that,” he recalls saying. The gynecologist, unperturbed, then told him she would take care of the situation herself. “And I was dismissed,” he says. “Here is a major vascular operation being done by a urologist, and a major complication, that is normally in our bailiwick of repairing, now being done by the gynecologist.”

These experiences led to a realization— and a resolution. “We, in vascular surgery, have missed the boat on this,” says Lumsden. So he set about building a vascular robotics program. Of late, that program has been gaining some interested glances from around the country following dissemination of a video from the popular Houston Methodist DeBakey CV Education YouTube channel via social media. The video features an inferior vena cava (IVC) filter removal procedure performed robotically. The surgery was led by his colleague, Charudatta Bavare, MD, who in a DeBakey Heart & Vascular Center grand rounds from September 2022, proposed robotic vascular surgery as an “un derexplored frontier,” raising the possibility that the open and endovascular era of the specialty may segue “into robotic vascular surgery in the future—that is the hope.”

Lumsden, who recently became president-elect of the Southern Association for Vascular Surgery (SAVS), stresses his role as “enabler” in this quest. For a long time, one of the challenges that held back vascular surgery was a lack of laparoscopic training, he points out. But these days, even many newer general surgeons “are now bypassing laparoscopic surgery and going straight to robotic,” he notes. “So this need for laparoscopic skills is not an absolute requirement to become a robotic surgeon.”

Lumsden sees his role as one of “pushing this along,” continuing: “You have got to learn the basics before you start taking on the big stuff. Charu[datta] Bavare is one of my mid-level partners, trained as a general surgeon, worked in the community in laparoscopic surgery, vascular surgery, general surgery—he had to go to what we call an underserved community—and he has got all the skills. If he can’t make this work, nobody can make it work.” In Houston, Bavare started out on “relatively trivial cases,” explains Lumsden. Cases that perhaps do not require a robot, he says. “But you have to get up to speed in a safe environment. And you have to get your team up to speed.” From procedures such as laparoscopic peritoneal dialysis placement and revisions, Bavare moved on to the likes of median arcuate ligament syndrome, and, now, the IVC filter removal. “We have a lot of people here who are sophisticated in robotics, all of whom are interested in helping us do this,” Lumsden relates. “There are these little pieces we need in other specialties that we are actively trying to seek out and grab, and pull this toward the vascular surgery community.”

Lumsden looks back to the man for whom his center is named, Michael E. DeBakey, MD, and his innovation of the Dacron graft, as he looks forward. “To this day, that is probably the single-most durable procedure that has been described for repairing the aorta.” The problem with that was a “not-so-hot” delivery system, which the endovascular revolution sought to remedy. “What we’ve essentially done is given up durability for a delivery system. And that means stent grafts,” he says.

“If you look at other specialties—urology, general surgery—when they went minimally invasive, they went laparoscopic or robotic. They did the same procedures that have been proven for 20, 30 years. They didn’t invent a whole new specialty called endovascular surgery the way we bought into it.”

Creating an artificial intelligence-based tool to help clinicians perform precision AAA analysis

Canadian researcher uses more than a decade’s worth of collected intelligence in abdominal aortic aneurysm (AAA) care to develop algorithms that will allow for forward prediction of disease risk—not just a real-time tool. By or University of Calgary, Alberta, Canada, vascular surgeon Randy Moore, MD, the route to a world of precision care for individual abdominal aortic aneurysm (AAA) patients—involving aortic wall strength-mapping technology developed over the course of the last 15 years, allied to an artificial intelligence (AI)-powered algorithm—is drawing nearer. Right now, says the associate professor of vascular and endovascular surgery, the decision to treat AAAs is based on a single diameter measure derived from population-based information. “That is flawed,” he implored. “And this hasn’t changed in over half a century.”

Moore was speaking during the 2023 Houston Aortic Symposium (March 16–18), held in Houston, Texas, where he delivered insight into RAW (Regional Areas of Weakness) Maps and its aim to provide a precision medicine solution for AAA patients. “When we look at size alone as a measure for patients at risk of aortic aneurysm disease, we ignore all these other things that are critical to our decision-making,” he told those gathered for a talk on the ViTAA Medical Solutions technology. Moore is the company’s medical director and a co-founder, and it is on his clinical experience that early testing of the tool’s effectiveness is based.

Moore emphasized the core principle behind AI in clinical work: analyzing large amounts of data, recognizing patterns, and predicting outcomes from pattern-recognition algorithms. “In our center, for the past 15 years, we have developed a number of algorithms that allow us to link actual tissue strength to risk in terms of wall strength analysis,” he said. The ViTAA solution he proposes uses a RAW mapping score of aortic wall tissue integrity so that clinicians can talk

Bryan Kay

through with patients the risk associated with their condition. “We knew our mapping technology was very effective at identifying wall strength and weakness,” he said. “But is that map a useful tool to allow for forward prediction—not just a map in real time but the ability to move ahead and provide the clinician with a tool?”

An initial pilot study of 36 patients showed a statistically significant correlation between ViTAA’s RAW Maps and aortic growth over time.

“We could, from a single ViTAA analysis, identify or predict risk in that patient moving forward up to 12 months with a statistically significant outcome,” Moore said. “We knew the mapping tool was good, but we wanted to understand how the addition of artificial intelligence would unlock, not just that mapping technique, but the predictive value moving forward.”

That’s where the ViTAA Aortic Model comes in, he continued. This involves the use of patient imaging—which the system “flattens out,” gathering 3,000 coordinates of the aorta—and comparisons between different aortic scans at “exactly the part of the aortic wall we want to address.” The model enables serial investigations, Moore said, and using explainable AI—unroofing the concept of black-box AI— clinicians can then see what’s being measured and modified for auditable purposes. “Our vision is that with the AI we have combined with the mapping technology, we are going to be able to provide the clinician with a go-forward view of a patient’s down-the-road behavior, which can then inform current real-time decision-making.”

Of course, the AI algorithm requires datasets from which to learn, Moore conceded. As with human facial recognition technology that generates people who do not exist, artificial patients, too, can be created. “Why would we do this?” asked Moore. In order to generate a large enough dataset so that the researchers can get the answers they need in a short period of time, he said. “You can generate human aortic characteristics without actually including any backtraceable, real patient data. How does this work? You take real patient data, feed it in, and a generative adversarial network then creates this synthetic dataset that you can learn to train your AI.”

Moore pointed to a concrete use case his team developed. “In our initial 16-patient pilot study looking at the strength of the aortic neck, we were able to identify a statistically significant relationship to a weak neck and subsequent type 1a endoleak. But if you look at the dataset, it was heavily weighted toward endoseal, with a small number of endoleaks. To make that learning set more applicable, we then created a synthetic database with 5,000 patients, with equipoise between the two groups. That took six minutes on a laptop.” After an analysis probing the synthetic database’s validity, the researchers found that it still produced what is considered a “very excellent” predictive rate.

Moore and colleagues are now focused on validating the model through a North American multi-site registry and a number of research-use only sites accumulating datasets on aortic pathology. “The future of precision aortic care ain’t what it used to be as some of these tools continue to roll out.”

A RECENT STUDY COMPARING OUTcomes of endovascular aneurysm repair (EVAR) patients has reported no statistically significant differences in mortality or secondary rupture rates between standard Cook, Medtronic and Gore endografts, suggesting similar safety in a real-world setting. Michael O. Falster, PhD, a senior research fellow from the Centre for Big Data Research in Health in Sydney, Australia, Ramon L. Varcoe, MBBS, a vascular surgeon from Prince of Wales Hospital, also in Sydney, Australia, and colleagues report this and other outcomes from a large population-based observational study in the European Journal of Vascular and Endovascular Surgery (EJVES).

Another key finding was that rates of subsequent aneurysm repair were higher for endografts other than Cook devices, but only statistically significant for Medtronic devices. In order to compare rates of all-cause death, secondary rupture and secondary intervention in their retrospective cohort study, Falster, Varcoe et al used a linked clinical registry (Australasian Vascular Audit [AVA]) and all-payer administrative data from patients undergoing EVAR for intact abdominal aortic aneurysm (AAA) between 2010 and 2019 in New South Wales, Australia.

The authors identified 2,874 eligible EVAR patients, with a median follow-up of 4.1 years and a maximum of 9.5 years.

Writing in EJVES, Falster, Varcoe and colleagues report similar mortality rates for patients receiving different devices, ranging between 7 and 7.3 per 100 person years. In addition, they reveal that there was no statistically significant difference between devices in secondary rupture rates (between 0.4–0.5 per 100 person years).

Furthermore, Falster, Varcoe et al note that patients receiving Medtronic and Gore devices tended to have higher crude rates of subsequent aneurysm repair (1.5 per 100 person years) than patients receiving Cook devices (0.8 per 100 person years). This finding, the authors write, remained in the adjusted analysis, but was only statistically significant for Medtronic devices.

“Major endograft devices have similar overall long-term safety profiles,” the authors summarize in their concluding statement. However, they add, there may be differences in rates of secondary intervention for some devices. “This may reflect endograft durability, or patient selection for different devices based on aneurysm anatomy,” Falster, Varcoe and colleagues posit.

According to the authors, this population-based study is one of the largest to compare outcomes of EVAR patients receiving contemporary endografts from different manufacturers.

The key strength of the present study, the authors claim, was the use of linked clinical registry and population-level administrative data. “This study is one of the largest to have explored outcomes for patients receiving different endografts, and also one of the only studies to have examined a contemporary cohort of patients to directly compare outcomes of endografts in current use,” Falster, Varcoe et al add.

The authors underscore “a need for ongoing surveillance of patient outcomes to compare and evaluate different devices used in clinical practice” to ensure those grafts are “providing the highest levels of safety and efficacy, with identification of those that are not.” They opine that the history of endovascular surgery is “littered with examples of underperforming endografts,” which, after evaluation, were “identified and managed by either temporary pause for device modification or withdrawal from the commercial market entirely.” The investigators stress that regulators such as the Food and Drug Administration (FDA) are “acutely aware” of the importance of postmarket data to assess the safety of devices and encourage surveillance programs. The present study, Falster, Varcoe et al claim, “demonstrates that linkage of clinical registry and administrative data can strengthen the evidence to help fill the inevitable gaps which occur when [randomized controlled trials] do not exist or are unethical to perform.”

“Continuous comparative assessments” are needed to guide evidence for treatment decisions across devices, they write in their closing remarks.—Jocelyn Hudson