Brain May Suffer Long After Heart Bypass
Thought Impairment Lingers Post-Surgery
July 15, 2002 -- Having surgery to save your heart may put your brain at risk. Two studies add new evidence that heart bypass surgery may have lasting effects on the mind.
More than 500,000 heart bypass surgeries are performed each year in the U.S. to restore blood flow to the heart. And although previous studies have suggested that many of these patients suffer from some type of thought impairment or impaired brain function up to six months after surgery, those effects have been hard to measure.
But by examining scans of patients' brains before and after heart bypass surgery, researchers say these studies offer new evidence that the procedure can affect the brain in both the short and long term.
In the first study, published in the July 2002 issue of The Archives of Neurology, a team of German researchers studied 35 patients under age 70 who had a heart bypass. Brain scans were taken before and after the surgery -- along with a series of tests to measure concentration, attention, short-term memory, and hand-eye coordination.
Researchers found new areas in the brain with reduced blood flow after the bypass in 26% of the patients. But having these lesions wasn't associated with any particular type of impairment, according to the skills tests.
The scans also revealed changes in how the brain reacted to certain compounds, which indicates cell damage. Patients who had these changes initially scored lower in their thinking tests, but their brain function returned to normal levels within 10-14 days after surgery.
Study researcher Martin Bendszus, MD, of the University of Wurzburg in Wurzburg, Germany, and colleagues, say inflammation in the brain caused by the surgery may have prompted the temporary decline in brain function. In addition, using a heart/lung machine to circulate the blood during surgery may create tiny air bubbles in the blood that can also lead to short-term brain damage.
In a second study, a research team from the University of North Carolina at Wilmington, found that these negative effects on the brain can last weeks after surgery.
They studied brain function in 39 patients one to two days before surgery and three to four weeks afterward and compared their results with those of 49 healthy adults. Their results appear in the July issue of Neuropsychology.
The researchers saw major differences between how the two groups performed on tests of attention and memory both before and after the surgery.
Prior to the procedure, bypass patients scored lower on memory tests, but researchers attribute the differences to pre-surgery anxiety as well as the underlying heart disease.
After the surgery, the comparison group performed better than the bypass patients on two important tests of attention and memory. The study authors say this finding confirms the notion that the brain systems that support attention may be most vulnerable to damage because they are among the most complex.
Researchers say the heart bypass procedure, like many major surgeries, exposes the brain and nervous system to unusual stress, such as inflammation, lack of oxygen, lowered body temperature, and powerful anesthesia medications, that may affect brain function.