Such clues would be highly desirable, because restenosis, as it is called, occurs in at least 20 percent of angioplasty patients, increasing their risks for heart attacks or strokes. More than half the time, there are no symptoms to indicate that danger exists, says Dr. Peter N. Ruygrok, a consultant cardiologist at Green Lane Hospital in Auckland who led the search.
"We tried to identify subgroups at high risk of restenosis, but it was difficult to tease out indicators," Ruygrok says.Medical technology could solve the problem, he says. A new generation of stents -- tubes inserted after angioplasty to hold vessels open -- has reduced the restenosis rate significantly in several large trials.
The Auckland physicians analyzed data on 2,690 patients who underwent angioplasty, in which a balloon is used to open clogged blood vessels. Of that group, 607 patients had blockages of 50 percent or greater in the treated arteries six months after the procedure, and 55 percent of those patients had no symptoms.
In hopes of finding indicators of risk, the researchers looked at 46 different factors, including age, gender, smoking history, use of heart medications and physical characteristics of the arteries. They came up with just three indicators of silent restenosis: gender (men are at greater risk than women), the diameter of the artery near the obstructed area and the extent of blockage found by an angiogram, a specialized X-ray, done six months after the angioplasty, says their report in the Nov. 6 issue of Circulation: Journal of the American Heart Association.
The researchers were hoping to come up with more and better indicators, Ruygrok says. In particular, they expected that persons with diabetes would be at higher risk of restenosis, but their data did not show that. In the end, "angiography is the only definite way to identify silent restenosis, but we don't believe we can advocate routine angiograms six months after angioplasty," Ruygrok says.
"We do not recommend routine angiograms, so most management of patients is driven by the development of symptoms or abnormal tests," says Dr. Sidney C. Smith, chief science officer of the American Heart Association.
The use of conventional stents "has reduced restenosis in large groups of patients but still has not eliminated it as a problem," Smith says.
A new generation of stents, which are coated with drugs to prevent re-blockage by interfering with the growth of the artery's muscle cells, could change the outlook, Smith and Ruygrok say.
New stent coatings "appear to hold real promise," Smith says. Two large-scale studies have found a high degree of effectiveness with one coating "and there may be other medications that effectively reduce restenosis. It could change how we do things," Smith says.
What To Do
Patients undergoing angioplasty can consult their doctors about the use of stents and the availability of the newer coated stents.