Red Oak Cardiovascular Center

ARTERY "SCAFFOLDING" HELPS KEEP THE BLOOD FLOWING…

For the better part of the twentieth century, "hardening of the arteries" -- or atherosclerosis -- has been associated with aging. Unfortunately, during the first half of the 1900's, this very common heart disease was often fatal. Today, this particular disease process is reasonably well understood, and medical science has given us several options for treating clogged coronary arteries successfully.

Most people know, for example, that fatty deposits, or plaque, can build up over time in the critical arteries that carry blood to the heart muscle. Depending on the extent of the blockage, this might bring on chest pain during exercise. If the blockage (occlusion) becomes extensive, or if a blood clot attaches to the sticky buildup and shuts off the coronary artery altogether, a heart attack occurs. This outcome, obviously, is to be avoided if at all possible.

It hasn't been too many years ago that a person's only option for dealing with obstructed coronary arteries was open heart surgery to reroute the blood flow around the blockage. Then, in September, 1997, in a hospital in Zurich, Switzerland, Dr. Andreas Gruentzig launched the new field of Interventional Cardiology by inserting a catheter into a patient's coronary artery, inflating a tiny balloon which opened a blockage, and restoring blood flow to the heart.

Twenty one years later, more than one million coronary angioplasties are performed each year around the world. According to the American Heart Association, 434,000 angioplasties were performed in 1995 (the latest year for which statistics are available) in the United States alone.

For the patients who are candidates for angioplasty, there are some significant benefits over open heart surgery. For many, this minimally invasive procedure works as well as surgery in reducing chest pain and improving quality of life. There is less risk with balloon angioplasty, as well as a significantly shorter recovery period, and the costs are also less.

There have been many advances in angioplasty procedures. While its use was once reserved for people with only one narrowed vessel, physicians are now able to offer this technique to people with more severe disease, and even in cases of multiple blockages.

Traditionally, about one third of the patients who undergo balloon angioplasty experience a return of the problem within about six months of the procedure. The plaque build-up returns, the blood flow is once again restricted, and there's a need for another procedure. Preventing this "restenosis" is the topic of considerable medical research, and progress is being reported all the time.

Since 1987, cardiologists have been using a tiny flexible metal coil or mesh tube -- called a stent -- to prop open a newly opened artery. After the artery is dilated and cleared by the balloon, the stent device is placed over the balloon catheter and maneuvered back into the problem area where the balloon reinflates and locks the stent into place. This creates a rigid "scaffolding" to hold back the plaque on the artery walls. Study after study has shown that -- while the use of a coronary stent can decrease a patient's need for additional angionplasty -- it markedly reduces their need for bypass surgery. The results and outcomes when stents are used have been so positive that now, in about 33 percent of the cases where angioplasty is performed, patients are also getting the stents to minimize the risk of the artery reclosing. Nothing is perfect, however, and even patients with stents can have problems with reclosure of the artery, and in some cases, clots can form on the inside of the "tube".

For the last several years, researchers around the world have been evaluating the outcome of procedures performed with stents coated with heparin, which is a natural blood clot-resistant substance. Traditionally, people who undergo angioplasty procedures, including the insertion of a stent, have been required to take one or more blood-thinning agents for a period of time following their procedure, and aspirin may be prescribed for use indefinitely. Unfortunately, several of these agents can cause some potentially dangerous side effects, including bleeding in the brain.

Study results of the "thromboresistant" (anti-clotting) capabilities of the heparin-coated stents have been extremely positive. Scientists reported fewer post-procedure cardiac "events" in patients who received the medication-coated device. As the phased studies progressed, researchers were able to significantly reduce the post-procedure administration of the anti-clotting drugs because the incidence of severe bleeding side-effects was zero, and there were no cases reported of clots forming in the stents. Subsequently, the use of heparin-coated stents has continued to increase.

Meanwhile, scientists are pursuing a wide range of promising therapies to prevent arteries from clogging up again. One of the most exciting is the prospect of gene therapy -- that is, introducing genetic material into the arterial wall itself -- immediately following, or coincident with the angioplasty procedure -- to halt the tissue growth that causes restenosis. Since atherosclerosis cannot be tracked to a single gene, ongoing research is aimed at switching on or off multiple genes' vulnerability to medication. This way, the cells that are responsible for generating the renewed tissue/plaque growth in the diseased area get a lethal dose and other cells are left untouched. The challenge at hand is the efficient delivery of the genetic material into the artery walls.