NEW YORK (Reuters Health) - In a new study of German heart patients, people who had invasive bypass surgery and those who underwent less-invasive stent placement showed declines in thinking and memory skills a few months after the procedures.

Doctors have long been concerned about cognitive decline in patients who undergo coronary artery bypass grafting (CABG) because of blocked arteries, and indeed, memory deficits were more significant after those procedures than after stenting.

Still, the findings don't prove it's the procedures themselves that cause memory decline -- it could just be that plaque buildup in blood vessels in both the heart and the brain is causing a variety of problems in the same patients.

These patients obviously all have atherosclerosis, said Dr. Mark Newman, who studies cognitive decline after cardiac surgery at the Duke University Medical Center in Durham, North Carolina.

If you have atherosclerosis in your coronary vessels, you probably have it in other vessels in your body as well.

Patients who are treated with CABG are often in a worse health state, with more buildup, than those who undergo stenting. It could be that cognitive decline after these procedures more relates to the severity of the atherosclerosis than the procedure itself, Newman, who wasn't involved in the new research, told Reuters Health. I think that's still a debate.

Even so, it makes sense that when built-up cholesterol in heart vessels is nudged loose during surgery, it could travel to the brain and cause problems there, researchers said.

The current study involved 37 patients getting a stent placed and another 47 undergoing CABG, mostly in their 60s and early 70s. Before and three months after the surgeries, the participants completed a series of thinking and memory tests, designed to measure how well they could come up with or remember certain words, symbols and pictures.

The changes in their test scores were compared to those from another 33 healthy volunteers.

Patients in the stent group had a greater drop in score on two out of the 10 tests, compared to controls, a few months after their procedures. Bypass patients' scores declined on seven of the tests.

Dr. Tibo Gerriets from Justus Liebig University in Giessen and colleagues write in the American Heart Journal that it hasn't been clear how much the cognitive changes that occur after heart procedures really bother people in their everyday lives.

But Newman said that for some patients, these kinds of changes in thinking and memory skills might be the difference between leading an independent life and needing extra help.

Dr. Todd Rosengart, head of cardiothoracic surgery at Stony Brook University Medical Center in New York, said that the risks of cognitive decline after bypass surgery depend on how the procedure is done -- and that doctors who performed the German surgeries might not have used the best techniques to protect patients against those risks.

Nowadays (doing a procedure) very well means not just getting the patient through the procedure with no mortality, it means getting them through the procedure in great shape, he told Reuters Health.

Heart patients, he said, shouldn't be afraid to ask their surgeons about the steps they're taking to protect their brain during procedures.

With a good surgeon at a good hospital, the chance of having thinking and memory problems related to bypass surgery shouldn't be greater than one in 20, Rosengart added.

Heart procedures are getting safer and safer, Newman agreed. I don't think that people should be overly concerned (about cognitive decline). I think they should have the right treatment that's going to help them overall, and look at ways that they can enhance their overall quality of life.

SOURCE: American Heart Journal, October 2011.

New York New York Medicine