In July, UAB Hospital became the first in the state to use a new implantable device that dissolves inside the human body to battle coronary artery disease.
The heart surgeons at UAB implanted a biodegradable stent called the Absorb GT1 Bioresorbable Vascular Scaffold System in a patient on July 20, just days after the Food and Drug Administration approved it on July 5. The dissolvable stent, developed by the Santa Clara, California-company Abbott Vascular, is now available for patients commercially.
Massoud Leesar, M.D., a professor in UAB’s Division of Cardiovascular Disease, led the surgery team that day. He says the device is a major advance in the treatment of coronary heart disease.
“The dissolvable stent is really important because, in the past, there was only one option, ” says Leesar. “The metal stent.”
The Absorb GT1 Bioresorbable Vascular Scaffold System is made of polylactide, a material that dissolves naturally, much like dissolving stitches and surgical sutures. The dissolving stent can support a diseased artery temporarily so normal blood flow can resume.
Abbott had previously chosen a select group of medical centers, including UAB, to test the dissolving stent in a clinical trial pending FDA approval.
“We had prior experience with it, ” says Leesar. “So when the FDA approved it, we were ready to use it. So it wasn’t our first experience. We had deployed this in several patients in the past.”
Absorb has now been approved in 100 countries and used in more than 150, 000 patients, says Abbott spokesperson Kristina Becker.
“In the United States, more than 100 centers and 2, 000 patients participated in the clinical trial that led to its FDA approval, ” she says.
The medical centers that are currently offering the Absorb stent include Good Samaritan Hospital in Los Angeles, University Hospitals Case Medical Center in Cleveland, Honor Health Scottsdale Shea Medical Center in Arizona and Northeast Georgia Medical Center in Gainesville.
Surgeons can use the stent to treat atherosclerosis, a condition caused by a build-up of cholesterol-containing plaque deposits inside the walls of coronary arteries.
Several factors and behaviors can lead to plaque-clogged arteries, including high blood pressure, diabetes, obesity and smoking. As the arteries become narrower, patients may experience symptoms such as chest pain and shortness of breath and even a heart attack.
More than 370, 000 people die from coronary artery disease each year, according to the National Heart, Lung and Blood Institute.
To repair a blocked artery, surgeons often perform a procedure called angioplasty, inserting a tubular stent into the artery to restore normal blood flow. Over the years, surgeons have used metal stents to widen the diseased arteries. Often, they have used stents that secrete medication into the artery wall to help keep plaque from forming.
The metal mesh stents, however, have some drawbacks, Leesar says.
“If a patient stops taking blood thinners after a few years, ” says Leesar, “occasionally we’ll see clotting that could lead to a heart attack. Because the stent is a part of the heart, we can’t remove it.”
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In contrast, the Absorb stent dissolves almost completely within three years, except for two tiny pairs of metallic marker beads at each end that remain in the artery so doctors in the future can see where surgeons placed the device. As the Abbott stents slowly dissolve, they help arteries to stay open on their own. Eventually, as new cells replace the device, the artery is better able to remain open.
Because the dissolving stent is temporary and not permanent like the metal stent, there is less chance for clotting, Leesar says.
“So when the patient stops taking blood thinners, ” says Leesar, “the [clotting] problem doesn’t occur anymore.”
Moreover, says Leesar, metal stents limit the artery’s ability to dilate. Therefore, some patients with metal stents may experience chest pain when the artery is unable to dilate with the natural demands of an individual’s daily activities. In contrast, a dissolvable stent allows an artery to dilate, pulse and flex with the varying demands on the heart.
Surgeons can implant the dissolving stent using a catheter that has a small balloon mounted on the end. The surgeons insert the catheter into a blood vessel in the groin or arm and move it into a coronary artery. Once the catheter is in place, doctors inflate the balloon, which expands the stent around it and stretches the artery wall. The balloon is then deflated, and the catheter is removed.
Like the traditional metal stent, the Absorb stent emits a medication to prevent inflammation and tissue growth in the artery. Over time, the stent breaks down into water and carbon dioxide, elements that occur naturally in the body.
The dissolvable stent, however, is not without risks, says Leesar. A device that is implanted improperly can lead to clotting and even a heart attack. Moreover, only patients who meet certain conditions are good candidates for the stent.
“The majority of patients can get the dissolvable device, ” Leesar says. “Some patients’ arteries, however, have a lot of calcium. If we see that the calcium is excessive, we will not put in this device because it can lead to clots or cause a bad reaction.”
Becker says that the company will not disclose the cost of the device for competitive reasons. Absorb, however, will be reimbursed as a drug-eluting stent under the current drug-eluting stent reimbursement codes.
Since the FDA approved the dissolvable stent, Leesar and his fellow heart surgeons at UAB have implanted about 20 of the devices, he says. The first person to receive a dissolving heart stent in the U.S. was a Mississippi patient, who received it during the 2012 investigational study.
In the study, published in the Nov. 12, 2015 issue of the New England Journal of Medicine, researchers compared Absorb with Abbott’s metallic, drug-coated stent called XIENCE. After a year, the study found no significant statistical difference in adverse reactions between Absorb and XIENCE in patients.
UAB’s cardiology department has pioneered other new medical advances as well. In 2012, UAB Heart and Vascular Services was the first in the state to offer the minimally invasive Edwards Lifesciences SAPIEN Transcatheter Aortic Valve Replacement (TAVR) for patients suffering from aortic stenosis, which is a hardening of the aortic valve. With TAVR, patients can undergo heart valve replacement without open-heart surgery. Leesar was one of several cardiologists at UAB to participate in the first surgery.
He says UAB’s reputation for cardiovascular care has helped to attract patients from across Alabama seeking treatment for complex heart conditions.
With the introduction of the dissolving stent, Leesar says UAB will now conduct studies that could lead to new protocols for using the stent that would allow for better deployment techniques and improved outcomes for coronary artery patients in the future.
“We must progress and advance, ” says Leesar, “and not to go back.”
Gail Allyn Short and Art Meripol are freelance contributors to Business Alabama. Both are based in Birmingham.
Text By GAIL ALLYN SHORT // Photos by ART MERIPOL
