TUESDAY, Feb. 8 (HealthDay News) -- High levels of certain blood
enzymes following coronary-artery bypass surgery can signal an
increased risk of death, a new study suggests.
For those with the highest enzyme levels, the risk of dying
within 30 days was double that of those with the lowest levels.
Elevated levels of creatine kinase or troponin are common after
bypass surgery, and small increases were not considered significant
until now, the researchers noted.
"When people have a bypass operation done sometimes there is some damage to the heart muscle, and chemicals are released that mark that," said study author Dr. Michael J. Domanski, from the Mount Sinai Cardiovascular Institute in New York City.
"What our study shows is that there is a strong graded association of enzyme elevation with mortality," he said. "More is worse, but even small amounts have an impact on mortality."
Domanski doesn't think that measuring these enzymes after
surgery would have any impact on treatment. However, he said that
since most of the heart damage occurs during surgery, these enzymes
could be measures of the quality of heart operations in different
"I'd rather have my bypass operation with somebody who has less enzyme elevation," he said. "The larger their enzyme elevations, the less I'd like to go to them."
The report is published in the Feb. 9 issue of the
Journal of the American Medical Association.
Domanski and his colleagues set out to study the effect of
elevated enzymes on short- and long-term patient outcome after
coronary-artery bypass surgery to replace blocked heart arteries.
To do this, they conducted a meta-analysis, which consists of
reviewing published studies to look for patterns.
They identified seven studies that included 18,908 patients who
underwent CABG and were followed for three months to five
Patients with even moderately increased levels of creatine
kinase or troponin after surgery were at greater risk of dying both
one month and five years after surgery, the researchers found.
While age, history of kidney disease and an earlier heart attack
were also associated with the risk of death, enzyme levels were
still the strongest predictor.
According to the authors, the findings need confirmation in
large clinical trials, but levels of these enzymes might one day be
used as markers for bypass surgery outcomes. Doctors often test for
elevated creatine kinase or troponin levels to confirm a heart
attack, but testing is not routinely done after bypass since these
patients usually get aggressive treatment with statins and other
Dr. Gregg Fonarow, a professor of cardiology at the University
of California, Los Angeles, said the findings could influence
"It is well-established that large increases in cardiac enzymes are associated with higher risk of subsequent mortality," Fonarow said. "However, the data as to whether smaller increases in cardiac enzymes are associated with increased risk have been mixed."
This new analysis suggests that elevations of these enzymes in
the first 24 hours after coronary artery bypass grafting (CABG)
surgery were associated with increased 30-day and one-year
mortality even in patients with modest elevations, compared with
patients who had no increase in enzyme levels, he said.
"Patients undergoing CABG who are found to have early elevations in cardiac enzymes should be recognized as being at higher risk for mortality and potentially treated more aggressively with cardiovascular protective medications," Fonarow said.
For more information on coronary artery bypass surgery, visit
American Heart Association.
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