TUESDAY, April 22 (HealthDay News) -- Hospitals that perform fewer cardiac bypass operations don't have more deaths following the procedure than hospitals that handle a greater number of bypasses, a new study says.

This finding contradicts conventional wisdom, which has assumed that hospitals that do more cardiac bypass operations have better results, with fewer patient deaths.

"Volume isn't the key ingredient or the driving force behind outcomes," said lead researcher Dr. Rocco Ricciardi, of the Lahey Clinic and Tufts University School of Medicine, in Massachusetts.

"We found over a long period of time that outcomes improved across the country no matter where you seek care," Ricciardi added. "It's been a gradual reduction in the number of coronary artery bypass graft cases performed because of the growth of less invasive techniques," such as angioplasty.

The study findings are published in the April issue of the Archives of Surgery.

In patients with coronary disease, the arteries that supply blood and oxygen to the heart become hardened and narrowed. If lifestyle modifications and medicines don't help, a doctor may recommend coronary artery bypass surgery (CABG). Surgeons take a piece of a vein from the leg or artery from the chest or wrist, and attach it to the coronary artery above and below the narrowed area or blockage. This allows blood to bypass the blockage, according to the U.S. National Library of Medicine.

For the study, Ricciardi and his colleagues collected data on 108,087,386 people admitted to U.S. hospitals from 1988 to 2003. Among these patients, 1,082,218 underwent cardiac bypass surgery.

Over the course of the 16-year study period, the rate of cardiac bypass surgeries increased from 7.2 cases per 1,000 patients in 1988 to 12.2 cases per 1,000 patients in 1997, before dropping back to 9.1 per 1,000 patients by 2003. During that same time span, the number of angioplasties tripled.

And from 1997 to 2003, the number of hospitals doing large numbers of cardiac bypass surgery dropped from 32.5 percent to 15.5 percent. Despite this shift, however, the death rate after cardiac bypass surgery dropped from 5.4 percent in 1988 to 3.3 percent in 2003, the researchers found.

What's more, the largest decrease in death rates was among the hospitals that performed the fewest cardiac bypass operations.

Ricciardi's team believes its findings show that using death rates after cardiac bypass surgery may no longer be an accurate gauge of the quality of care provided by a hospital.

"Measuring quality is obviously difficult," Ricciardi said. "Trying to determine which hospital will give you the best outcome, and where you get the best quality medicine, is very difficult to determine based solely on surgical volume."

Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles, said he agrees with the findings. And they mirror the conclusions of other studies, he added.

"This new study adds to other recent studies which suggest that volume of cardiovascular procedures is, in and of itself, not a useful indicator of quality of care or patient outcomes," he said.

"The very good news from this study is that in-hospital mortality rates for CABG are improving at U.S. hospitals, irrespective of CABG volume," Fonarow said.

Fonarow said the volume of procedures should not continue to be used as a measure of quality care.

"The practice of health-care payers and accrediting organizations in using volume of procedures such as CABG surgery as quality criteria for hospitals should be replaced with more accurate and direct measures of quality of care and patient-centered clinical outcomes," he said.

Another expert, Dr. Samin Sharma, director of interventional cardiology at Mount Sinai Medical Center in New York City, said the death rate from cardiac bypass surgery has dropped because the procedure has become standardized and surgeons feel comfortable performing it.

"Volume used to play a major role, but now it turns out to be that volume may not be that important," Sharma said. "More important are protocols and systems that you put in place that really make a change in the outcome in mortality. People have put protocols in place that improve outcomes, whether it's a low-volume center or a high-volume center."

More information

For more on cardiac bypass surgery, visit the U.S. National Library of Medicine.