Angioplasty with stents may be a more cost-effective option than bypass surgery for many patients with severe cases of clogged heart arteries, according to study data that come amid a growing U.S. focus on cost-conscious medicine.

Both methods improved patients' quality of life over one year, while bypass surgery gave patients slightly better relief from chest pain. The one-year data from the "Syntax" study were released Saturday at the American College of Cardiology's annual conference.

Doctors said the study is limited at this point by its duration, because trends regarding costs evolve over time. That view could mute the study's impact if doctors wait to learn more about longer-term outcomes - Syntax will continue tracking patients through five years.

Patients who have clogs in three coronary arteries or the left-main artery, which is a crucial supplier of blood to heart tissue, tend to have bypass surgery today to address these problems. But there has long been debate about whether less-invasive procedures involving tiny stent scaffolds might also work.

The 1,800-patient Syntax study, sponsored by stent-maker Boston Scientific Corp. (BSX), failed to show stents measured up when data were released last year - there was a higher rate of major events among stent patients compared with bypass patients. That result was tipped by the increased rate of repeat procedures for stent recipients, while the combined rates of death, heart attacks and strokes were similar in both groups.

The study used drug-coated "Taxus" stents from Boston Scientific. Coated stents use medication to combat scar-tissue growth, which can close off arteries again, and comprise a $4 billion global market where rivals include Abbott Laboratories (ABT), Johnson & Johnson (JNJ) and Medtronic Inc. (MDT). Tapping likely bypass patients could represent a way to expand a growth-challenged sector.

While some surgeons saw clear validation for their treatment method in initial Syntax data, there were also some helpful data points for stent proponents. The key was a subdivision of patients based on the complexity of their heart problems - bypass looked best for the most complex group, but there were similar rates of adverse events between stent and bypass patients in low and moderately complex groups.

A similar result showed up in the fresh data on cost and quality-of-life attributes for each procedure. In this case, when these heart-disease patients are again stratified by complexity, stents provided a cost benefit for easier and more moderate cases. Costs after one year were $6,154 lower for the simpler stent cases compared with bypass, for example.

The cost difference narrowed a bit for moderate patients and then were about the same for the third of patients who had really complex problems. Considering an analysis called "quality-adjusted life expectancy" was also better for bypass patients in this group, these data seem to further support bypass as the right option in these cases.

The data have limitations, including the fact that researchers had to apply U.S. health-care costs for procedures done overseas and the one-year timeline. Bypass surgery was significantly more expensive out of the gate - even though stent patients required 4.6 devices on average - but stent patients closed some of the cost gap over time due to their higher rate of repeat procedures.

"The open question is will this gap in costs narrow further with longer follow-up or will it be stable," said Mark Hlatky, professor of health policy at Stanford University, during his review of Syntax at a conference session. "I think we need further follow-up to figure that out."

Dr. Robert Guyton, chief of cardiothoracic surgery at Emory University Hospital in Atlanta, said in an interview he expects the gap to close over time. After three years, he thinks the sickest two-thirds of patients will look like clear bypass candidates, rather than the one-third of complex patients the current datamost clearly point to.

David Cohen, the doctor who presented Syntax data Saturday, and director of cardiovascular research at Saint-Luke's Mid America Heart Institute in Kansas City, also expects the cost differences to narrow further. He said the gap is unlikely to close for the least-complex patients, however.

Cohen has received research grants from Boston Scientific.

-By Jon Kamp, Dow Jones Newswires; 617-654-6728; jon.kamp@dowjones.com