Some heart bypass patients are receiving cardiac stem cell transplants to try to repair damage.

This week, a 67-year-old James Culross from Toronto will be discharged from Toronto General Hospital after having 2.83 million stem cells injected into seven sites where his heart had been damaged by a heart attack in November.

When someone suffers a heart attack, part of the heart muscle dies and is replaced by a scar. In larger heart attacks, the patient can develop heart failure — a weakening of the heart that leaves the patient short of breath, said cardiac surgeon Dr. Terrence Yau of Toronto's University Health Network.

Heart patient James Culross was the donor and recipient of his own stem cells. (CBC)

Yau and his colleagues at Toronto General's Peter Munk Cardiac Centre and Maisonneuve-Rosemont Hospital in Montreal are involved in a clinical trial testing the safety, effectiveness and feasibility of injecting stem cells into the hearts of people having bypass surgery.

"This kind of therapy can improve the function and blood flow of hearts that have been injured by heart attacks most commonly and potentially by other means as well," said Yau.

About 50,000 Canadians are diagnosed with advanced heart failure each year. On average, men live only 18 months and women three years after diagnosis.

While angioplasty, bypass surgery and stents can prevent new heart attacks, they don't reverse exisiting damage. A new heart is the only known treatment for that, but transplants are invasive and expensive, and there is a lack of available donor organs.

That's where the stem cells could come in.

Stem cells taken from marrow

In Culross's case, the stem cells were taken from the bone marrow in the hip and lower back in the operating suite. After four to six hours, the stem cells were isolated, the bypass grafts done and the stem cells injected back into the damaged areas of his heart.

"I thought it was great," Culross said of the procedure. "It's your stem cells, nobody else's."

Culross is now working on improving his strength and walking more in the hopes of returning to his auto body repair job.

Since 2010, eight patients have also had the experimental procedure in Montreal.

The Montreal and Toronto teams plan to combine their findings once each has results on 20 patients.

No one knows yet whether the stem cell treatment will improve survival or quality of life by healing the heart.

Investigators worldwide are testing whether giving stem cells after a heart attack works better than existing therapies.

With files from CBC's Kelly Crowe