COLUMBIA — New advances in medical research have brought heart stents to the forefront of heart health. Research is now being conducted to improve drug-eluting heart stents to reduce the risk of blood clots forming after stents are placed.
A team of researchers is testing whether coating heart stents with a human protein could prevent the re-narrowing of coronary arteries after balloon angioplasty procedures.
Who gets heart stents and why? Stents are used with angioplasty to prop the artery open to keep it open better and longer. Without stents, arteries are more likely to become blocked again, cutting off blood flow.
What are the potential complications associated with heart stents? Restenosis (reclosing) can occur over time, just like with simple angioplasty. Blood clots could also form, sometimes months after the procedure. Patients must continue to take their anti-clotting drugs as instructed after the surgery.
Can a patient have multiple stents? Yes.
How often do stent patients end up having bypass surgery? Usually, patients have one procedure or the other, but it isn’t uncommon for a patient to have both. The procedures can occur close together, or be separated by many years.
How many people have heart stents? More than 500,000 heart stents are placed each year in the U.S.
Sources: William Fay, director of the division of cardiovascular medicine for MU, and americanheart.org
The project brings together scientists William Fay, a professor of internal medicine, medical pharmacology and physiology, and director of the division of cardiovascular medicine for MU; Daniel Lawrence, a professor of cardiovascular medicine at the University of Michigan; Douglas Bowles, an associate professor of biomedical sciences at MU; and Brian Wamhoff, an assistant professor of cardiovascular medicine and biomedical engineering at the University of Virginia.
A heart stent, an alternative to invasive bypass surgery, is used to reopen blocked arteries. The stents are placed after an angioplasty — a procedure in which a small balloon is fed through the femoral artery to the blocked artery and then inflated to reopen the artery.
In the past, angioplasty has been the only treatment. But in recent years, doctors have been using the balloons to place stents, which prop the artery open to keep blood flowing.
Bare-metal stents consist of wire mesh without any type of coating. This type of stent can allow the smooth muscle cells that cause arterial blockage to re-form.
“Small cells can regrow through a stent like snowflakes getting through chicken wire and building up,” Fay said.
Drug-eluting stents are coated with drugs that inhibit cells from dividing and causing re-narrowing in the cleared arteries.
"However, these drugs also inhibit the growth of the endothelial cells that coat the inner lining of blood vessels," Fay said, "which renders the artery vulnerable to blood clot formation, which can cause heart attack."
The researchers hope the human protein being studied, called plasminogen activator inhibitor 1, or PAI-1, will halt the growth of bad cells while still encouraging the good ones to grow, Fay said.
Lawrence, from the University of Michigan, has been studying PAI-1 in his lab for more than 20 years and is hopeful it can control cell growth.
The three-year PAI-1 project will be funded through a grant from the MU Life Sciences Research Trust Fund and will be carried out in two parts.
Fay and Lawrence will continue their research on PAI-1 and its effects on smooth muscle cells and the effects of drug-eluting heart stents on blocked arteries. On the other end of the project, Bowles, the associate professor of biomedical sciences for MU, will study live results of angioplasty in pigs.
Both Fay and Lawrence have worked with mice in the past. But for the studies to advance, “the subjects have to graduate and become something more akin to humans. Pigs are the closest subject for this,” Fay said.
The project has been many years in the making. It's being carried out with extreme care for humane treatment of the animals, with the help of MU's vet school, Fay said.
MU "is the only (university) in the state and one of the few in the nation where both (a medical school and veterinary medicine school) exist on the same campus,” Fay said.
Advances in medical technology aren't the only goals of the project. The researchers are hopeful the collaboration of multiple scientists across the nation will lead to the creation of more interactive research groups leading to new developments for small businesses that could provide the new technology for these projects, as well.
"We're looking beyond our own molecule," Fay said, "to serve the broader community for advancing science and technology."