New stent appears safe and effective for preventing arteries from reclosing in coronary heart disease patients

May 6 2004

The small study of 42 patients compared standard stents — metal mesh tubes used to keep vessels open after balloon angioplasty — with a new stent coated with the drug everolimus in a biodegradable polymer.

The experimental stent releases everolimus, an immunosuppressant and an antiproliferation agent similar to sirolimus, one of two drugs used for coating stents that the U.S. Food and Drug Administration approved in the last year.  Everolimus has shown promise at preventing heart and kidney rejection after transplantation.  It acts by inhibiting cell reproduction and reducing cell growth.

The two drug-releasing stents approved for clinical use retain their polymer coatings as long as they are in the body.  Most of the polymer coating used on the everolimus stents tested in this study biologically dissolved in a month or so, leaving only the metal stent behind.

“This unique everolimus-coated stent freezes the biological process that leads to the renarrowing of arteries after catheter-based treatments,” said Peter J. Fitzgerald, M.D., Ph.D., senior author and an associate professor of medicine and engineering at Stanford University Medical Center in Palo Alto, Calif.  “Not only are the patients free from symptoms, but they have open arteries 12 months after stent implantation.”

Fitzgerald’s intravascular core lab at Stanford analyzed the data.  The randomized study was conducted at the Heart Center in Siegburg, Germany, by Eberhard Grube, M.D., Shinjo Sonoda, M.D., and colleagues.

The patients’ average age was 64.  Twenty-seven received the everolimus-coated stents and 15 got bare-metal stents.  Both groups were similar in age, sex, prior heart attacks, smoking, diabetes and hypertension.

The study’s main clinical focus was on major adverse cardiac events (death, bypass surgery, a revascularization procedure on the stent-treated artery, or heart attack).  Only two patients in the everolimus group and one in the control group suffered an event during the first six months and one patient died of chronic obstructive pulmonary disease, which was unrelated to the stent treatment.

No other major events occurred during the last six months of the study.  

Before the study, patients in the coated-stent group had artery narrowing of 64.1 percent.  At six-month follow-up, the narrowing was only 2.6 percent.  Among the bare stent group, artery narrowing was 62.1 percent before the study and 27.8 percent at six-month follow-up.

Fitzgerald and his colleagues found that after one year, patients who got the everolimus-coated stents had 87 percent less narrowing in the treated portion of their arteries than those who received the uncoated or bare-metal stents.

The introduction of balloon angioplasty a quarter century ago allowed physicians to open coronary arteries narrowed by fatty deposits and restore blood flow to ailing hearts.  However, many patients’ arteries later narrowed again.  Evidence showed a major reason was a biological reaction to the procedure that resulted in excessive growth of smooth-muscle cells lining the inside of blood vessels.

In the early 1990s, physicians began placing metal stents in reopened arteries to help them stay open.  But many patients’ vessels still renarrowed.

“The minute you put a bare stent in a vessel, you get a biological response that can result in occlusion 25 percent of the time,” Fitzgerald said.  “With coated stents, you get the mechanical properties of the stent with a far lesser biological reaction to cause occlusion.”

Researchers then experimented with metal stents coated with polymers that released drugs that retard the growth of vessel-wall cells.  Such drugs need less than a month to inhibit the cells’ proliferation.

The polymer on the stents tested in this study are biodegradable.  “Metal, once it gets encased in the vessel wall, becomes inert,” Fitzgerald said.  “You only need the polymer to deliver the drug.”

Other co-authors are Fumiaki Ikeno, M.D.; Yasuhiro Honda, M.D.; Saibal Kar, M.D.; Charles Chan, M.B.Ch.B.; Ulrich Gerckens, M.D.; and Alexandra J. Lansky, M.D.