Early Access to New Treatments for Aortic Disease

A healthy aorta supplies the rest of the human body with blood the way the Mississippi River sends its tributaries into the heartland. But an aneurysm or a penetrating ulcer can make patients so ill that the very surgery to cure them is risky.

At the Center for Aortic Disease at University of Maryland Medical Center (UMMC), patients with acute aortic disease, including those too sick for open surgery, can receive treatments not yet available elsewhere.

Because of their vast experience in aortic disease, surgeons at UMMC serve as investigators on a clinical trial for the first thoracic aortic endograft available in the United States that seals off lesions in a neighboring artery, as well as for another trial for a device with four side branches for arteries that supply the abdominal organs. 

The center treats both acute and chronic aortic syndromes, including aneurysms, dissections, penetrating ulcers and intramural hematomas. The co-director of the center is University of Maryland School of Medicine faculty Shahab Toursavadkohi, MD, assistant professor of surgery.

In a collaborative model seen at just a few centers in the country, Dr. Toursavadkohi, a vascular surgeon, collaborates with heart surgeons and vascular medicine doctors to fix complex aortic problems. The team brings complementary strengths to the operating table.

"We can treat very complicated aortic diseases that other places are likely not capable of doing," Dr. Toursavadkohi says. The Center for Aortic Disease is also part of the University of Maryland Heart and Vascular Center.

"The main thing that can impact the outcome is early treatment in a high-volume center by high-volume medical teams," Dr. Toursavadkohi notes, with a multidisciplinary "army of people" treating some of the most challenging aortic conditions nearly every day.

When Open Surgery Is Too Risky

For patients with aortic dissections -- tears in the wall of the aorta -- the standard fix involves open surgery. However, Dr. Toursavadkohi notes that affected patients tend to be older, with multiple comorbidities and barely pumping hearts, making surgery risky.

"Typically, these people will go on medical management and hospice, and their outcome is extremely poor, " Dr. Toursavadkohi says.

Nonetheless, blood can escape through the tears and become trapped. Downstream tissues may starve. Trapped blood could weaken and burst the aorta. 

Seeking better outcomes, the Center for Aortic Disease is pioneering the use of minimally invasive techniques to fix these dissections. [AH1] 

The repair starts with a cut into the groin, through which surgeons thread the catheter used to send guide wires and a stent graft to the injured spot. Once positioned, the endograft lines the weakened part of the aorta, bolstering it and rerouting blood.

If the lesion sits near the heart, the organ might pump away the endograft before it reaches its destination. Therefore, surgeons rapid-pace [AH2] the heart to, say, 200 beats per minute, so that it quivers without moving blood.

"We then drop the blood pressure to almost no pulsatility,” he says. “That gives you a few seconds to land the graft precisely where you need to." 

"These people are extubated the next day, and they feel good,” Dr. Toursavadkohi says. 

Similar considerations underlie the treatment of large and fast-growing aneurysms. With those as well, a stent graft inserted through a small portal makes a fix possible in patients who cannot tolerate open surgery.

Clinical Trial Opportunities for Patients

To reinforce the aorta with no leakage, an endograft must fit properly.

"One of the issues that we have is, if you don't have a graft specifically designed for a particular segment of the aorta, then the size is not going to match," says Dr. Toursavadkohi. A graft that is too long might block blood flow to side vessels fed by the aorta, perhaps causing a stroke. Too short, and the surgeon might have to piece together something from materials on hand, a process that takes time when every moment counts.

To meet such challenges, medical device makers have been developing new stent grafts and testing them in clinical trials. The UM Center for Aortic Disease aids those efforts by serving as a test site.  For example, two years ago, the center finished testing the Gore Excluder iliac branch endoprosthesis (IBE). Approved by the US Food and Drug Administration in 2016, it gives surgeons a ready-made option for patients with aortic aneurysms involving the iliac artery, which supplies the legs and pelvis.

Before the IBE became available, many patients who had undergone endovascular repair experienced pain when walking, from ischemia caused by a poorly sealing graft. The new device addresses that problem by preserving blood flow to the iliac arteries.

"We were the only center that had access to that graft for about two years," recalls Dr. Toursavadkohi. To date, the IBE remains the only branching aortic device sold in the United States.

In 2014, the UM Center for Aortic Disease became the first to implant the Gore TAG thoracic branch endoprosthesis (TBE) into a patient, launching a big multicenter clinical trial.The first endoprosthesis in the United States to offer branching for the thoracic aorta, the TBE mends aneurysms and dissections in the aortic arch and descending thoracic aorta.

“By using this device, we avoid doing open surgery in these patients, and yet we are doing a complete endovascular repair," says Dr. Toursavadkohi.

Additionally, he looks forward to testing the Gore Excluder thoracoabdominal multibranch endoprosthesis (TAMBE). W.L. Gore & Associates, which also makes Gore-Tex fabric, granted UM preliminary approval before other sites due to its experience with its products.

The TAMBE isolates aortic aneurysms and dissections that affect vessels that feed the viscera. It comes with four side-branching tubes, enabling treatment of multiple vessels at the same time without opening the ribcage. The TAMBE comes in a range of sizes to ensure a better seal. Since these lesions would otherwise require a huge surgery plagued by complications, Dr. Toursavadkohi considers the TAMBE a breakthrough.

”This is an opportunity for us to treat these people and save lives," he says.