The first open surgical repair of an abdominal aortic aneurysm (AAA), which involved resection and replacement with a cadaver homograft, was performed by French physician Charles Dubost in Paris in March 1951. Surgery remained the only treatment technique for AAAs for nearly 40 years. The first clinical case of minimally invasive endovascular aneurysm repair (EVAR) was performed on September 7, 1990, by groundbreaking vascular surgeon Juan Parodi in Buenos Aires, Argentina.1

The story of EVAR since that time has been one of continuous development. The initial devices that Parodi developed and utilized consisted of a tube-shaped aorto-aortic graft sutured at each end to a balloon-expandable stent based on the design of radiologist Julio Palmaz. In 1994, this basic approach evolved into bifurcated devices resembling a pair of pants, which quickly became popular. From there, single-piece systems evolved into multicomponent devices of two, three, or even more segments. Today, there is a wide range of modular stent grafts available that includes multiple configurations and sizes of components to better suit various challenging anatomies.

Delivery systems have also progressed. Catheters that were initially rigid and bulky became narrower and much more flexible, allowing improved access in tortuous vessels. In addition, stent graft material and design have changed in various ways to improve conformability, reduce fracture, and minimize rates of device migration.

EVAR is now a commonly available option for a growing population of patients requiring treatment for AAAs. Some advantages of EVAR over traditional open surgery include shorter hospital stays, fewer postoperative complications, and greatly reduced recovery time; the treatment technique may also result in less operative blood loss. New devices with fenestrations and branches have increased the number of patients who are good candidates for EVAR, reducing the population of individuals who would otherwise be resigned to “watchful waiting” for their aneurysms. Recent research now demonstrates that EVAR offers reduced mortality rates compared with open repair.2

Endovascular Today spoke with three specialists who were instrumental in the birth and development of this lifesaving treatment technique. Leaders in their field, Drs. Juan Parodi, Claudio Schönholz, and Michael Marin, took some time to recall and reflect on the early days of EVAR and commented on the present and future of this important procedure.

INSPIRATION

The development of EVAR was inspired by the needs of patients, specifically those with AAAs who were too highrisk to undergo traditional open surgical repair. “In 1976, I was a resident at the Cleveland Clinic, and we had two consecutive patients who had bad outcomes after AAA repair,” said Parodi, who later worked at the University of Illinois before returning to the Instituto Cardiovascular de Buenos Aires in Argentina. “I thought to myself, ‘If, in this high-quality hospital and with superb surgeons, the results of this operation are not always good, the cause should be inherent to the procedure, which is too traumatic for these old and debilitated patients.”

Patients with AAAs are usually older, have coronary issues, renal insufficiency, lung issues, and perhaps even previous abdominal surgeries, which can lead to the condition known as “hostile abdomen.” All of these comorbidities make open surgery even more difficult and risky, if it remains an option at all for such patients.

Dr. Marin, a vascular surgeon based in the United States, echoed Parodi's sentiment. “The interest and drive were uniform across the world—we were all on the search for a less-invasive way to treat a complex disease in often very sick patients. Ultimately, we offered the new procedure first only to patients who had large aneurysms but who would not survive surgery.”

Parodi had been learning the Seldinger technique from a radiology colleague, and he had become aware that most patients with aneurysms had large femoral arteries. “My initial idea was to use a big catheter guided by a guidewire,” said Parodi. His vision was specific. “The catheter would contain a thin graft attached to a ‘cage' of metal (with the graft sutured outside the cage). A stainless steel elastic wire forming a ring with a zigzag configuration would be compressed and then released (in a spring-loaded fashion) from the large catheter. Using fluoroscopy, the device could be deployed to cover the aneurysm.” At this time, there were no such grafts available, meaning Parodi would have to design and construct the device himself. In time, he utilized this approach in numerous in vitro and canine trials, but not without difficulties.

EARLY CHALLENGES

Initially, the main goal of EVAR was to reinforce the aorta via an endoluminal approach. It was clear that a graft was needed, but as Schönholz noted, “the question was how to fix the graft to the inner lumen.” Parodi had performed extensive animal research utilizing his homemade device, but migration was a true challenge, and the ability to keep the device fixed to the aortic neck remained elusive.

Parodi initially had to use nylon fabric instead of DACRON Material for the graft and a plastic tube as a sheath; this wireless solution proved to be less than ideal. “It was hard to advance the sheath into the aorta,” he said, “because of the sharp edge on the plastic tube.” Yet, another obstacle was the need to develop a device that was not too bulky but could still completely exclude the aneurysm upon deployment.

“It seems obvious now, 20 years later,” said Schönholz, “but he needed something that could be small enough when introduced to navigate from the femoral to the iliac to the aorta and then be able to grow to a size to cover an aortic neck that is potentially 24 mm or larger in diameter.”

ADVANCEMENTS AND ADAPTATIONS

In 1988, Parodi met Dr. Julio Palmaz at Georgetown University, where he was presenting animal research using the novel balloon-expandable stent that he had designed. The PALMAZ Stent for aortic valvuloplasty had a maximum diameter of 10 mm, which was not large enough to anchor a device within the abdominal aorta. However, the balloon-expandable stent held the potential for inspiration and experimentation. “I told him about my project,” said Parodi. “Initially, he was not very excited, but he agreed to collaborate with me.”

Back in Buenos Aires, Parodi took a sample of the PALMAZ Stent to bioengineer Hector D. Barone, who was able to reproduce a scaled-up version using electroerosion and electropolishing. “I then decided to replace the spring-loaded system with the balloon-expandable one,” said Parodi. The new device incorporated a thin-walled DACRON Graft attached to the custom-made, upsized balloon-expandable stents. “The idea was to replace the vascular suture with the stent in both ends, and eventually in three ends, using an aortobi-iliac device (not yet developed at that time),” said Parodi.

It was time for EVAR to be put to the test. “After doing extensive in vitro and animal studies, we designed a device for patients,” said Parodi. This set included a stiff guidewire, a TEFLON Sheath with a valve at the end, a valvuloplasty balloon, and an extra-large PALMAZ Stent that could be expanded up to 28 mm in diameter. “A nose cone was formed at the end of the sheath by inflating the protruding end of the balloon with a small amount of saline solution,” Parodi explained. “The stent attached to the graft was compressed and applied over the balloon. Gold markers were sutured at the end of the graft.” The sheath used in 1990 to perform that first-ever EVAR procedure in a patient measured a bulky 27 F, Schönholz recalled. “It was also very rigid and primitive,” he said. But, most importantly, it worked.

On that day, Parodi and his colleagues performed two AAA procedures—the endovascular one as well as an open surgical repair in another patient. After the procedures were completed, Parodi invited Palmaz to have dinner with him at a nearby restaurant. When they returned to the hospital to check on their patients, the individual who had undergone EVAR was sitting up, enjoying his own dinner, and the surgical patient was still intubated.

EVAR IN AMERICA

In 1992, Parodi, Schönholz, and Barone traveled to New York to meet with Marin and Dr. Frank Veith. They were coming together to perform the first EVAR in America, utilizing a handmade device that Parodi had brought from Argentina and carried with him in the airplane cabin.

“I want to make it very clear that Parodi was the one testing and proving the EVAR concept,” Marin said. “He was able to visualize and come up with solutions to complex problems, and he was very generous with his knowledge. We had previously met in Milwaukee to discuss treatment possibilities for a patient of mine. When Parodi brought the device and performed the procedure in New York, that step initiated the whole process here. It became important to figure out how to continue to do these procedures.”

From that point, Marin began to build his own devices, with modifications to make them easier to use. “I learned the techniques from Barone,” he said. “Then I approached the US Food and Drug Administration (FDA) for an investigator-sponsored investigational device exemption study.” His institution provided support, as well as room. “I set up a clean workspace environment in the hospital and sent the finished devices out to be gas sterilized. I built more than 200 devices,” Marin said. “For each case, I would build two in order to have a backup.”

A SOLID SOLUTION

In order for EVAR to become an accepted first-line therapy for even a select population of patients, certain technological milestones had to be met. “We needed the development of durable grafts that would not break down after implantation through wear and tear,” said Marin. “It took an understanding of the bioengineering of the prostheses and knowledge of where forces were being applied.” As clinicians began performing an increasing number of EVAR procedures, limitations became more apparent, and device manufacturers stepped up to create solutions.

The first-generation GORE® EXCLUDER® AAA Endoprosthesis (Gore & Associates, Flagstaff, AZ) received FDA approval in 2002. This device had been previously approved in Argentina. “I had the honor of using the first GORE® EXCLUDER® Device in South America,” Parodi said, “and it was very good from the beginning.”

In keeping with the company's reputation for responsiveness, Gore moved quickly when it was discovered that the original device could be improved. In Argentina, Schönholz was acting as a proctor for Gore at the time. “The company does close follow-up of patients who receive the devices, and they are always looking for ways to improve their technology. By 2004, clinicians had discovered that some patients treated with the device had aneurysms that were not shrinking; in fact, some were growing. These were not leaks—the substance in the sac was not blood, it was serous fluid. It was the result of selective permeation across the graft material.”

This situation became referred to as “endotension,” and Gore responded by adding a layer of low-permeability material to the graft. The second-generation GORE® EXCLUDER® Device effectively addressed the endotension problem. “The technology is now durable,” said Schönholz. “We still see some patients with the first GORE® EXCLUDER® Device, and for those few that have a growing sac due to endotension, we reline those stent grafts with the newer-generation device.”

Gore has since brought additional components onto the market every few years to expand the indications for their device, including new sizes for the stent graft main body and limbs. In 2010, the company released the GORE® C3® Delivery System. “We can now control how and where we deploy the device to the point that we can do a delivery, and if we don't like where it has landed, we can actually reconstrain and reposition the device,” said Schönholz. According to Parodi, the GORE® C3® Delivery System is “magnificent.”

THE FUTURE

It seems clear that EVAR procedures will only increase in frequency. With the number of FDA-approved devices and the variety of modular device iterations available, practitioners are less often finding that open surgery is necessarily the better option. “Almost always, the only reason I do open surgery now is if the patient's anatomy is not conducive to EVAR,” said Marin, “and those cases are becoming fewer and fewer.” The bottom line is that EVAR is less invasive and better tolerated by patients. “Of course, there are still some anatomic limitations,” said Schönholz, “but even ruptured AAAs are being treated more and more by the endovascular approach.” In Schönholz's group at MUSC, 80% of cases are treated with EVAR, “and this is not unique to just the United States—it is around the world. Many practitioners are using just EVAR whenever they can.”

Manufacturers, including Gore, are supporting this global drive for increased access to EVAR. More complicated devices including features such as fenestrations and branches are being developed to address anatomic barriers. The phenomena of physicians using chimney grafts (also referred to as “snorkels”) certainly points out yet another likely avenue for device companies to explore.3 Ultimately, the future of EVAR technology will be decided by the ingenuity and creativity of physicians, biomedical engineers, and others who continue to work together to further refine this life-saving treatment technique.

  1. Parodi JC, Palmaz JC, Barone HD. Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg. 1991;5:491-499.
  2. Jackson RS, Chang DC, Freischlag JA. Comparison of long-term survival after open vs endovascular repair of intact abdominal aortic aneurysm among Medicare beneficiaries. JAMA. 2012;307:1621-1628.
  3. Criado FJ. Commentary: use of chimneys, snorkels, and periscopes to preserve aortic branches during endograft repair. J Endovasc Ther. 2010;17:221.