It's a question that divides cardiac surgeons — is it better and safer to perform bypass surgery with the patient on a heart-lung machine that stands in for the heart, or to do it on a pulsing organ still pumping blood to the body?

For a number of years, a debate has raged about whether so-called on-pump or off-pump surgery produces better results and whether the latter reduces the risk of complications such as cognitive losses known in cardiology circles as "pump head."

Over the next seven years, a Canadian-financed and -led study will try to answer the questions, studying what happens when 4,700 patients from 16 countries are randomly assigned to either the traditional on-pump or the newer off-pump technique.

"You have the believers [in the off-pump approach] and the non-believers," said Dr. Andre Lamy, a cardiac surgeon at McMaster University in Hamilton who is leading the study along with renowned McMaster cardiologist Dr. Salim Yusuf.

"So with this study, we're trying to figure out if the technique is really safe and on top of that, if there's any benefits for the patients for stroke and pump head and so on."

For the record, Lamy suspects off-pump will turn out to be superior, at least for older, sicker patients.

But no large randomized trial comparing the two techniques has been done, despite the fact the off-pump method has been in use for a least a decade. Without the reliable evidence such a trial would generate, "I don't know the answer. I truly don't," he said.

Canadian Institutes of Health Research to fund study

The trial — the largest to date to compare the two approaches — is being funded through a $6.5-million grant from the Canadian Institutes of Health Research.

A cardiac anesthesiologist from Duke University in Durham, N.C., welcomed the news, saying the trial is "absolutely needed."

"We tried to do it in the United States, but the NIH [National Institutes of Health] never gave us the funding that we needed," said Dr. Mark Newman, chair of the department of anesthesiology at Duke.

"So I think it's great that the Canadians are going to be able to do it. Because … everybody has their opinion and each surgeon believes something different, based on his own practice. So I think you won't really know until you have a good randomized trial."

The study is designed to compare the safety profiles over the short- and long-term of the two techniques, measuring things like whether one or the other has lower rates of death, post-surgery neuro-cognitive losses, stroke, blood transfusions and quality-of-life concerns.

A key question will be whether, as hoped, off-pump surgery leads to fewer complaints of the memory loss and cognitive impairment that have come to be known as pump head or bypass brain.

It's a commonly seen but not commonly warned-about phenomenon: People who are placed on a heart-lung machine during their surgery can wake up foggy-brained and confused. While the cause is not clear, a theory is that people who undergo the surgery while on the machine may produce tiny clots that travel to the brain and cause mini-strokes.

A study by Newman and colleagues from Duke published in the New England Journal of Medicine in 2001 showed slightly more than 50 per cent of bypass patients suffered cognitive decline at the time of discharge from hospital. Followup five years later showed 42 per cent still sustained cognitive losses.

The Canadian trial — which will go by the name the Coronary trial — will enrol middle- to high-risk patients. It will follow patients for an average of five years after surgery, will look to see if there are higher rates of repeat bypass surgery or more procedures to insert artery-opening stents in the off-pump group.