Stents

with Robert Roth, M.D., Interventional Cardiologist, Columbia St. Mary’s

Posted: Feb. 1, 2004

The drug-eluting stent is the latest innovation in cardiac care, but it’s hardly the first. Interventional cardiology has been around since 400 BC, when catheters made from hollow reeds and pipes were used to study the heart valves of cadavers. In-between there has been cardiac catheterization, bypass surgery and, in 1978, balloon angioplasty. That procedure enabled doctors to clear blocked arteries and successfully restore blood flow to and from the heart.

Prior to angioplasty, open heart surgery was the only option for people with severely blocked arteries. But balloon angioplasty, the procedure in which a catheter is inserted into a coronary artery and inflated, also had its drawbacks.

Robert Roth, M.D., Interventional Cardiologist, Columbia St. Mary's "The major limits of angioplasty have always been a recurrence of disease or a chance of damaging the artery while we're doing the procedure, which has required emergency bypass surgery. The thing that has really changed that drastically has been the stent."

“The major limits of angioplasty have always been a recurrence of disease or a chance of damaging the artery while we’re doing the procedure, which has required emergency bypass surgery,” said Dr. Robert Roth, interventional cardiologist at Columbia St. Mary’s. “The thing that has really changed that drastically has been the stent.”

A stent is a tiny metal tube mounted on a balloon and inserted in the artery during an angioplasty. Once inside the coronary artery, the stent is opened, latching onto the artery walls, where it functions as a scaffold, helping the artery to remain an open passageway.

To say the stent has revolutionized interventional cardiology would not be an overstatement.

“With the advent of the stent, the chances of needing an emergency surgery have decreased to about one half of one percent,” Dr. Roth said. “In the first days of angioplasty it was about 20 percent. So the stent has made the need for emergency surgery extremely unlikely now (for balloon angioplasties).”

In addition, the restenosis rate, or recurrence of a blockage, also has been reduced through use of the coronary stent. Without stent insertion, Dr. Roth said, about one-third of patients needed another procedure within the first year of having the initial balloon angioplasty. The first stents, which were made of bare metal and came into use in 1995, cut that number in half.

Coated stent
“But we still have a 15 to 18 percent chance for a recurrence,” he said, “so the next evolution is the coated stent, also known as the drug-eluting stent.”

The drug-eluting stent was a response to cases in which blockages recurred. What doctors discovered was that the initial cause of the blockage – a buildup of fatty esters and cholesterol-laden plaque – was not the culprit.

“When analysis was done on the recurrent blockages,” Dr. Roth said, “it turned out that it was cell growth from the walls that made up the artery. It was basically scar tissue, just as you’d have on the skin.”

The solution, called brachytherapy, involves passing radioactive pellets through a catheter, using the same procedure used to insert a balloon. But in this case, the catheter is placed in the position of the recurrent lesion; the pellets sit for four minutes and are then pulled out.

The treatment, which is similar to radiation therapies used to treat cancer, has been effective in stopping the unwanted cell growth and keeping the artery open.

The drug-eluting stent was designed to eliminate the need for brachytherapy. It’s a metal stent with a polymer coating, but within the coating is a cancer drug called rapamycin.

“What it does,” Dr. Roth said, “is block cell growth, and it only works if it’s in direct contact with the cells. So any cells the drug comes into contact with will be inhibited and won’t grow. So, rather than treating the cells that grow back with brachytherapy, we can prevent them in the first place.”

The drug-eluting stent is so new that currently only one manufacturer, Johnson & Johnson, has been approved by the Federal Drug Administration (FDA) to market their stent in the United States. A second company, Boston Scientific, will begin selling stents this year. What that means to cardiac patients is that metal stents will be the norm for awhile. While a metal stent costs approximately $900, said Dr. Roth, the rapamycin-coated stent is priced at nearly $3,000.

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