People in better shape heading into bypass surgery are less
likely to die shortly following the procedure than those who are less fit,
according to a new study.
"We were not surprised because it makes intuitive sense
that those patients who are not fit are going to do poorly with a large
operation," said Dr James Smith, the lead author of the study and an
interventional cardiology fellow at Beaumont Health System in Royal Oak,
The findings echo results from earlier studies showing that
patients with a greater exercise capacity tend to do better after transplant,
weight loss and other surgeries.
Smith said none of those studies looked at heart surgery,
however, so he and his colleagues collected data from 596 patients who had
undergone coronary artery bypass grafting at their hospitals.
The operation involves transplanting a healthy artery from
another part of the body to the heart as a detour around a coronary artery that
is blocked by plaque. According to the National Institutes of Health, it is the
most common type of heart surgery among adults.
In the three months before their surgery, all of the
patients in the study who were in their 60s, on average had gone through a treadmill stress test,
which involves walking on a treadmill while heart rate and breathing are
Patients' exercise capacity, or cardiorespiratory fitness,
was measured in units called metabolic equivalents (METs). A MET of five is
about as strenuous as walking up a flight of stairs. Jogging is equal to about
seven METs and walking to about three. There were 78 patients who maxed out at
a score below five METs on the stress test and were therefore considered not
Smith's team found that four patients in the unfit group
or 5% died during their surgery, while five out of 518 patients in
the fit group, just 1%, died. The pattern was similar for people who died within
one month of the surgery and after other patient characteristics were taken
into account, the researchers reported in The American Journal of Cardiology.
Smith said it's not entirely clear why those who performed
worse on the stress test were more likely to die after bypass
surgery."Those with lower fitness may actually have, for whatever reason,
a technically more challenging surgery," he told Reuters Health.
The body's ability to cope with physical stress is also
likely to be involved, researchers said. Michael Trenell, a physiologist at
Newcastle University in the UK who was not involved in the study, said cardiorespiratory fitness is a useful (marker) of the body's ability to
deal with stress, whether that be exercise or surgical stress.
The same physiological systems in the body are involved in
both. Trenell said in an email to Reuters Health that studies from his
research group and others are beginning to look at whether improving cardiac
fitness before surgery can increase patients' chances of survival.
The challenge for some surgeries, including heart bypass, is
that there is not much time to intervene between diagnosis and operation. Smith
said exercise capacity could perhaps inform doctors and patients about the
risks tied to an operation and whether alternative treatments such as inserting
a stent should be explored.
Oftentimes exercise capacity is incorporated into
discussions for each individual patient, but is not part of a standardised risk
assessment, he said.
Smith's study couldn't go so far as to determine whether
some patients would have done better with an alternative treatment. He added
that the study was small, and "further investigation is warranted to
underscore the findings here to make sure they are valid".