People undergoing bypass surgery to improve blood flow to the heart are more likely to suffer a stroke afterward than those who have a stent inserted instead, according to a new look at past evidence.

Researchers collected data from 19 studies that included almost 11,000 patients with blocked arteries who were randomly chosen to have bypass surgery or to get a stent, used to prop open unhealthy blood vessels.

Taken together, that data showed patients in the bypass group were three times more likely to have a stroke while recovering from their heart procedure.

Bypass surgery is more invasive than inserting a stent: it involves grafting a healthy blood vessel around a blocked one, so blood “bypasses” the unhealthy vessel. For a stent procedure, a small mesh tube is inserted into the blood vessel. Certain stents also release drugs to keep clots from forming.

“There are some patients with coronary artery disease where clearly angioplasty (inserting a stent) is the best, least invasive way to go,” said Dr. Gregg Stone from Columbia University Medical Center in New York, who worked on the study.

“And there are other patients where that (damage) is just so extensive where clearly surgery is the way to go,” he said.

But in at least half of heart patients, Stone told Reuters Health, both bypass surgery and inserting a stent are valid options - and in those cases, stroke risk could be an important factor to consider.

“That knowledge could impact whether a patient or physician would prefer one versus the other,” Stone said.

“When you talk to most patients, many patients would rather die than have a stroke.”

Close to 800,000 Americans have a stroke every year, according to the American Heart Association.

The 19 studies included in the new analysis typically involved patients in their 60s, on average, most of who were men.

One month after the heart procedures, 12 out of every 1,000 bypass patients had suffered a stroke, compared to three to four out of every 1,000 who had a stent inserted.

That means 155 heart patients would have to get a stent instead of bypass surgery to prevent one stroke, Stone and his colleagues reported this week in the Journal of the American College of Cardiology.

At one year - as far out as they tracked patients - there were still more total strokes in the bypass group than the stent group.

Stone and the other researchers couldn’t account for the possible effects of traditional risk factors for stroke, such as diabetes. They also didn’t have data on how many people in the studies ended up dying from their strokes.

Still, Stone said changes in blood pressure during bypass and a clamp that’s used on the vessels around the heart could both increase the chance of blood to the brain being blocked.

In general, he said, there’s “so much more manipulation of the heart” during a bypass procedure.

Stone and one of his co-authors reported consulting and other financial relationships with companies that produce stents, including Medtronic and Boston Scientific.

The highest risk of stroke after a bypass is really in the first day or two after the procedure, according to Dr. Farzan Filsoufi, a heart surgeon at The Mount Sinai Medical Center in New York who didn’t participate in the new research.

After that, he told Reuters Health, whether patients have a stroke has more to do with their other risk factors than which procedure they had.

Filsoufi added that upgrades in technology have helped researchers lower the risk of stroke during and right after bypass surgery in recent years.

It’s still a higher risk than inserting a stent, he said, but patients who opt for a stent are more likely to end up needing the surgery repeated.

“That’s basically the trade-off,” Filsoufi said.

SOURCE: Journal of the American College of Cardiology, online August 20, 2012.