In contrast to trial results, actual clinical experience indicates that patients who receive conventional on-pump procedures are more likely to survive 3 years without need for another procedure than patients treated with an off-pump technique, according to an article in the February 18th issue of the Journal of the American College of Cardiology.

"If you looked up other studies, you would come to the conclusion that the off-pump procedure is the better way to go; but [these results] certainly show that conclusion is not borne out by this study that was done in a larger setting," said Edward L. Hannan, PhD.

Rather than a controlled trial in which a small, selected set of patients is randomized to receive a particular operation, the researchers took an observational approach in order to see happened in the real world of routine clinical practice. Because the state of New York collects, and makes public, information on every bypass procedure, the researchers were able to compare outcomes from 9,135 off-pump coronary artery bypass graft procedures and 59,044 conventional on-pump bypass operations that were done from 1997 to 2000.

Short-term survival rates were not significantly different for the two procedures. However, on-pump patients had higher three-year survival (adjusted risk ratio [RR] = 1.086, p = 0.045) and higher freedom from death or revascularization (adjusted RR = 1.232, p < 0.001).

Hannan noted that operating on a beating heart during an off-pump procedure can be technically challenging. In order to look for improvement in outcomes as surgeons gained more experience, the researchers did a separate analysis using data from only the final two years of the study period.

"When we did that we found that the long-term mortality between the two groups was not significantly different, but there was still an advantage for the on-pump patients in the long-term freedom from death or revascularization," he said.

There were some differences between the patients receiving each type of bypass surgery. The off-pump group had a significantly higher prevalence rate of older patients, women, and African-Americans. The off-pump patients also were more likely to show signs of heart failure, stroke, and some other diseases, as well as previous open-heart surgery. Patients who underwent an on-pump procedure were more likely to have just had a myocardial infarction, to have had CPR, and to have more coronary artery disease. However, when researchers analyzed their data to try to control for these differences in the patient groups, Hannan said the results still indicated an advantage for the on-pump procedure.

The newer, off-pump procedure has been gaining popularity in part because of reports linking the conventional on-pump procedure to potential problems with mental function. However, this study did not address that issue because mental status and neurological information is not included in the database.

Michael M. Madani, MD, who was not part of the research team, said that although the current study is a powerful analysis of a very large database, the results paint a picture only of the early days of off-pump bypass surgery. He pointed out that the devices used to stabilize the graft area during an off-pump bypass procedure were still evolving during the late 1990s. He said the devices now being used didn't become available until about the time the study period ended.

"The authors pointed out that some of the key findings, like the three-year survival benefit for the on-pump patients, were no longer there when they looked at the most recent data. In fact, when they limited it to the last two years of the study period, it seemed like the data was more in favor of the off-pump procedure," Madani asserted.