Heart patients often experience lasting problems with memory,
language and other cognitive skills after bypass surgery.
However, these problems aren't caused by the surgery itself
or the pump used to replace heart function during surgery,
a new study by Johns Hopkins researchers suggests. The
findings may lead to better approaches to prevent cognitive
decline regardless of which treatment heart disease patients
The study, published in the May Annals of Neurology,
compared cognitive function of patients who received cardiac
bypass surgery with that of patients who received other
treatments for coronary artery disease, including
pharmaceuticals and stents. After testing all the study
subjects periodically in a variety of cognitive areas for
six years after their treatments, the researchers found that
the groups experienced an almost identical decline in
cognitive function. The results suggest that the disease
itself, and not any particular treatment, is the cause.
Previous studies have linked bypass surgery to patients'
mental decline, with many doctors blaming the bypass pump
that keeps blood flowing through the body during surgery.
This research led many doctors to avoid recommending surgery
to their patients. However, Johns Hopkins researcher
Guy McKhann says that previous
studies hadn't compared patients who had bypass surgery to
those who had other treatments. Because of this, it's been
unknown whether mental decline is a consequence of surgery
using the bypass pump, heart troubles, part of the normal
aging process or another cause altogether.
To gather evidence, McKhann and other Johns Hopkins
researchers recruited 152 heart disease patients who were
scheduled to undergo bypass surgery and 92 patients whose
doctors planned to treat their heart disease in other ways,
including with stents and medications. The patients, mostly
men, had an average age of about 64.
Before the patients' treatments, the researchers gave each of
them a battery of 15 mental tests meant to examine cognitive
functions including memory, motor speed, attention and the
ability to plan ahead. Then, at three months, one year,
three years and six years after treatment, the researchers
gave the volunteers the same tests to see whether their
cognitive function had changed.
When they compared the two groups' results, the researchers
found similar changes. The groups started out with
comparable cognitive abilities, which improved slightly for
about a year after treatment; over the next five years, most
of the patients experienced a similar decline of cognitive
function in almost every area tested, regardless of whether
they had had surgery or another treatment.
These results, McKhann says, suggest that neither bypass
surgery nor the pump causes cognitive decline. He says that
the finding may help erase the stigma that prevents some
doctors from recommending bypass surgery.
"We don't think fear of mental changes should be a factor in
deciding what kinds of treatments you have for your heart,"
Since both groups of patients scored lower than healthy
patients on similar cognitive tests in other studies,
McKhann notes that he and other researchers believe that
coronary artery disease itself is the culprit. However, he
says, he and his colleagues don't believe that cognitive
decline is an inevitable consequence of heart disease.
"If we take a very aggressive approach to treating risk
factors for heart disease, including keeping a handle on
diabetes, blood pressure and weight, patients may be able to
avoid these cognitive problems," McKhann said.
Other Johns Hopkins researchers who participated in the study
are Ola Selnes, Maura Grega, Maryanne Bailey, Luu Pham,
Scott Zeger and William Baumgartner.
The study was supported by grants from the National Institute
of Neurological Disorders and Stroke, Charles A. Dana
Foundation and General Clinical Research Center at the Johns
Hopkins Medical Institutions.