Interview with Dr. Hans H. Bauer, MD, FACC
Medical Director, Cardiac Catheterization Lab, Our Lady of Lourdes Medical Center, Camden; Medical Director, Cardiac Catheterization Lab, Lourdes Medical Center of Burlington County
Drug-eluting stents, approved by the Food and Drug Administration for the treatment of coronary artery disease in the U.S. in April 2003, have been shown to be effective in reducing substantially the incidence of restenosis in the affected arteries. However, FDA tracking of incidences of acute thrombosis associated with the stents has gained media attention and raised public concern about the safety of the implants.
Dr. Hans H. Bauer pointed out that, while the seriousness of thrombosis cannot be minimized for patients who experience it, FDA tracking of reported stent-associated thromboses reflects a rate of much less than one percent. "The reported incidence is no higher, or, if anything, lower with the drug-eluting stent than with bare metal stents," Dr. Bauer said.
Dr. Bauer said the Cypher Sirolimus-Eluting Coronary Stent (Cypher stent), made by Cordis Corporation, a subsidiary of Johnson & Johnson, has reduced the rate of reblockage to single digits - four to five percent. This compares to a rate of 30-40 percent with balloon angioplasty, the technology introduced in the 1970s. The introduction of bare metal stents for angioplasty in the mid-1990s cut the rate to 15-20 percent. Thus the new stents, in which the drug Sirolimus is released from a polymer coating the stainless steel mesh structure of the device, represent a significant advance. The drug inhibits cell growth inside the stent to keep the artery open.
The body reacts initially to the presence of a stent as it does to any foreign object - by clotting, which, in turn, poses a risk of thrombosis. A bare metal stent will be covered with new normal tissue in about a month. To minimize the risk during that period, patients must begin a regimen of aspirin and Plavix and remain on the drugs for at least a month. Patients with drug-eluting stents, however, must remain on the regimen for at least three months, preferably longer if there is no contraindication.
Dr. Bauer pointed out that patients who experience restenosis after stent implantation usually present sub-acutely with chest pain and other warning signs that are addressable but that thrombosis occurs without warning. He therefore emphasized the importance of patients strictly maintaining the anti-coagulant regimen after implantation.
According to Dr. Bauer, the catheterization lab at Our Lady of Lourdes has implanted more than 1,000 drug-eluting stents since April. Physicians of Associated Cardiovascular Consultants have implanted over 600 of them. Dr. Bauer said thromboses have occurred among those patients, but they have been rare. "You can count on one hand the number of acute thromboses we've had," he said. "In almost every case, it was because the patient did not take aspirin and Plavix as directed. It's important to stress to patients that drug-eluting stents are pro-thrombotic for a longer time than bare metal stents. Aspirin and Plavix should not be stopped for the first three months unless there is a life-threatening bleeding emergency."
Dr. Bauer said not every patient with coronary artery disease would benefit from the drug-eluting stent. "The benefit is greatest in patients with long lesions in relatively small-caliber arteries," he said, "particularly diabetic patients."
Patients who probably should not receive drug-eluting stents include:
- Those with bleeding disorders, especially gastrointestinal bleeding.
- Patients who are not reliable or compliant in taking the necessary anti-platelet medications.
- Patients who anticipate surgery within the next six months.
- Patients with malignant tumors that may bleed.
Dr. Bauer added that the drug-eluting stents have not yet been proven to be beneficial in saphenous vein grafts or in patients who have experienced restenosis with bare metal stents.
Stents from other manufacturers using drugs other than Sirolimus are in various stages of study and development. Dr. Bauer anticipates that such innovations as time-release stents, covered with small reservoirs of various drugs, could be the next innovation in stent technology.In summary:
- Drug-eluting stents are effective in substantially reducing the incidence of restenosis.
- These stents are thrombogenic for a longer period of time and require a strict regimen of aspirin and Plavix for at least three months after implantation.