A typical over-the-wire angioplasty balloon

Angioplasty balloon catheters come in a wide range of lengths and diameters, and are made from a variety of materials, but the major shared characteristic is that the balloon can inflate to a certain diameter and not beyond, thus allowing a predictable opening. The positioning of the balloon at the stenosis, its inflation and the resulting increased flow post-angioplasty are all carefully viewed under fluoroscopy by the interventionist. Several inflations are usually made before the procedure is considered finished.

Even if the stent is utilized as the primary therapy, the process still involves a balloon, for the stent itself is mounted on an angioplasty balloon in order for it to be delivered to the diseased area and deployed. The balloon is inflated, and the stent along with it. When the balloon is deflated and withdrawn, the stent remains in place, serving as a permanent scaffolding for the newly widened artery. Within a few weeks, the natural lining of the artery, called the endothelium, grows over the metallic surface of the stent.

Stents have virtually eliminated many of the complications that used to accompany "plain old balloon angioplasty" (POBA) such as abrupt and unpredictable closure of the vessel which resulted in emergency bypass surgery. The additional structural strength of the stent can also help keep the artery open while the healing process progresses.

A typical stent mounted on a balloon

Drug-Eluting Stents A new type of stent, the drug-eluting stent or DES, has recently become the overwhelming choice of cardiologists. Two types are currently available in the in the United States: Boston Scientific's TAXUS paclitaxel-eluting stent and the CYPHER sirolimus-eluting stent, made by Johnson & Johnson / Cordis. Both stents are basically a bare metal stent that has been coated with a slow-to-moderate-release drug formulation, embedded in a polymer. It is hoped that the medicine used will prevent or at least reduce restenosis, reclosure of the coronary artery, one of the biggest limitations of angioplasty and causes for repeat procedures.

When the stent is placed, the drug is released over time directly to the area most likely to reblock. Two types of drugs currently are being used: an immunosuppressive agent, sirolimus, and a chemotherapeutic drug, paclitaxel. Both have proven effective in clinical trials that are currently underway, bringing the restenosis rate from the 25-30% range down to low single digits. If the very positive results from these devices prove to be durable over time, many have said that drug-eluting stents will revolutionize the treatment of coronary artery disease. (For more information on drug-eluting stents, see our "HOT TOPIC" on the subject.)

Angioplasty and Acute Myocardial Infarction
The emergency treatment of heart attack, or acute myocardial infarction, has been dramatically affected by these interventional devices. The combined use of balloons, stents, and a variety of new drugs literally can stop a heart attack in its tracks by quickly dissolving the clot, or thrombus, opening up the obstruction, and restoring normal blood flow — minimizing damage to the heart muscle itself. (For more information on angioplasty in the setting of Acute Myocardial Infarction, see our "HOT TOPIC" on the subject.)

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