Angioplasty and Stents

Percutaneous transluminal coronary angioplasty (PTCA), usually simply called angioplasty, involves opening the blocked artery.

Click the icon to see an animation about percutaneous transluminal coronary angioplasty.

A typical angioplasty procedure follows these steps:

• The surgeon threads a narrow catheter (a tube) containing a fiber optic camera directly to the blocked vessel.
• The doctor opens the blocked vessel using balloon angioplasty, in which the surgeon passes a tiny deflated balloon through the catheter to the vessel.
• The balloon is inflated to compress the plaque against the walls of the artery, flattening it out so that blood can once again flow through the blood vessel freely.
• In order to keep the artery open afterwards, surgeons use a device called a coronary stent, an expandable metal mesh tube that is implanted during angioplasty at the site of the blockage. (In some cases, a stent may be used as the initial opening device instead of balloon angioplasty.)
• Once in place, the stent pushes against the wall of the artery to keep it open.

Click the icon to see an animation about percutaneous transluminal coronary angioplasty.

Complications occur in about 10% of patients (about 80% within the first day). Outcomes are better in hospital settings with experienced teams and backup.

Click the icon to see an illustrated series detailing coronary artery balloon angioplasty surgery.

The most important long-term complication is reclosure (restenosis), which can lead to heart attack if not treated with a repeat procedure. Stenting and other advances have helped significantly in preventing reclosure and reducing heart attack rates. Nevertheless, a repeat procedure is still needed to restore the opening in 10 - 15% of procedures that use stents. Radiation therapies and stents coated with immunosuppressive drugs may significantly reduce these rates.

Recuperation

Angioplasty is less invasive than bypass surgery, requiring only one night in the hospital. Recuperation takes about a week. Chest pain after the procedure is very common and usually due to problems other than ischemia. Mild chest pain is even more common when a stent is used, possibly because the artery is stretched.

Preventing Reclosure and Blockage During or Shortly after Angioplasty

Reclosure of the artery during or shortly after angioplasty often occurs. A number of anti-clotting drugs are used to help prevent this.

• Aspirin and the anti-platelet drug clopidogrel are often used to prevent reclosure during the procedure.
• A high dose of the anticoagulant heparin is typically given before the operation.
• Intravenous glycoprotein IIb/IIIa inhibitors, powerful drugs that block platelets, also prevent reclosure after stenting in many high-risk patients, and evidence now strongly suggests that they reduce rates of heart attack and death. Eptifibatide (Integrilin) and tirofiban (Aggrastat) are the standard drugs used during angioplasty. They may be most effective if administered during angioplasty, rather than beforehand.

All of these drugs pose a risk for bleeding complications.

Preventing Artery Narrowing (Restenosis) Over Time

Narrowing or reclosing of the artery (restenosis) can occur within a year of angioplasty or even longer in 15 - 60% of angioplasty patients. Coronary stents, anti-clotting drugs, and other advances have reduced these events significantly, but have not eliminated the problem. Theories for the cause of restenosis include:

• The release of oxidants (damaging unstable particles) at the surgical site may cause injury and activate immune factors that produce cellular overgrowth in smooth muscles of the blood vessels.
• Other activities, including scarring, may remodel and narrow the blood vessels. (This is most likely the reason for restenosis in stented patients.)

Symptoms of restenosis include chest pain on exertion. (Heart attacks, however, do not usually occur with such events.) The narrowing of the artery in this case is not due to blood clots, so anti-clotting drugs are not useful. Restenosis usually requires a repeat operation. A number of approaches, mostly investigative, have been developed to prevent restenosis after angioplasty.

Sirolimus- and Other Drug-Coated Stents. Stents coated with the drug sirolimus (Rapamune), also called rapamycin, are generating great excitement. This drug blocks immune factors that cause cell proliferation and inflammation. It also has antibiotic properties. In an important 2002 study, none of the patients who were given the coated stent experienced reclosure, and 94% of them were free of any adverse heart events. In comparison, 27% of patients in the noncoated group experienced restenosis, while only 71% of them were free of adverse heart events. Researchers are also investigating stents coated with the cancer drug paclitaxel. Studies suggest that these drug-coated stents may be especially important options for patients with diabetes who undergo angioplasty. Patients with diabetes are more likely to experience re-narrowing of the heart arteries than other patients.

Coronary Artery Brachytherapy. Radiation treatment called coronary artery brachytherapy (Gamma One, Beta-Cath) can slow the cell growth in the arteries which causes restenosis. With this approach, any blockage in the stent is first removed, and a tube with an inflatable balloon is inserted. The surgeon then implants a temporary device that delivers radiation. Brachytherapy has shown excellent results in preventing restenosis and significantly reducing heart events and improving survival. Brachytherapy is also showing promise in preventing restenosis in stented artery grafts that were put in place after bypass surgery and later failed. However, several 2006 studies in the Journal of the American Medical Association indicated that sirolimus- and paclitaxel-coated stents may work better than brachytherapy in preventing restenosis in failed stents. In these studies, the drug-coated stents were inserted inside the original bare metal stents.

Medications. A number of medications are being studied for prevention of restenosis, although benefits to date have been modest. Other drugs under investigation include statins, various anti-clotting drugs, and B vitamins.

Other Procedures. Other procedures under investigation to keep the arteries open use ultrasound, "soft" x-rays, and cryotherapy (very low temperatures).