Until recently, patients undergoing coronary artery bypass graft (CABG) surgery were often put on an artificial heart pump. That changed recently with the introduction of a "off-pump" surgical technique, but researchers are learning that the new surgery method doesn't help in the long-run.

One year after surgery, the rate of cognitive decline remains about the same, according to an article in the Journal of the American Medical Association (JAMA).

Diederik Van Dijk, M.D., Cor J. Kalkman, M.D., of the University Medical Center Utrecht, the Netherlands, and colleagues studied 281 patients who underwent CABG surgery.

Of the participants, 139 were assigned to on-pump surgery, in which the patient's heart is stopped beating and an external pump is used instead to keep blood circulating, known as cardiopulmonary bypass. 142 were assigned to a newer off-pump surgery, in which just the area of the heart operated on is immobilized with the use of the cardiopulmonary bypass pump.

The patients were tested for cognitive dysfunction by a battery of 10 neuropsychological tests before surgery and at 3 and 12 months postsurgery.

"Patients who received their first CABG surgery without cardiopulmonary bypass had improved cognitive outcomes 3 months after the procedure, but the effects were limited and negligible at 12 months," the authors stated.

At three months, according to the authors, the incidence of cognitive decline was 21% in the off-pump group and 29% in the on-pump group. This difference was minimized after 12 months, with 31% of the off-pump group and 33% of the on-pump group exhibiting decline.

The authors also pointed out that use of cardiopulmonary bypass is associated with brain death -- known as cerebral morbidity -- and that previous research suggests approximately one in four patients will have cognitive decline two months after cardiac bypass surgery.