Calcium
channel blockers appear to significantly reduce risk for myocardial
infarction and other complications after heart surgery
Calcium channel blockers appear to significantly
reduce risk for myocardial infarction and other cardiac complications
following heart surgery, according to an article in the May 7th
issue of the Journal of the American College of Cardiology. The
meta-analysis, the first systematic review to examine use of the
drug class during heart surgery, concluded that drug use significantly
reduced rates of ischemia, myocardial infarction, and supraventricular
tachyarrhythmias.
"I had a graduate student [lead author
Duminda N. Wijeysundera, MD] who came to me and said, 'I'd like
to take a look at this.' My own personal bias at the time was that
he was probably not going to find anything, but he went ahead and
did it, and I was sort of surprised with what he found," said
W. Scott Beattie, MD, PhD, a coauthor of the study.
The current study evaluated the findings of
41 studies representing 3,327 patients. All of the studies were
randomized, controlled trials of calcium channel blockers used immediately
before, during, or immediately after heart surgery.
Overall, calcium channel blockers significantly
reduced the risk of myocardial infarction and ischemia. Some drugs
appeared to provide more benefit than others. For instance, the
drugs classified as non-dihydropyridines significantly reduced supraventricular
tachyarrhythmia. Although the results did not achieve statistical
significance, calcium channel blockers were also associated with
a trend toward lower mortality during coronary bypass surgery.
"When you actually look at all of the
evidence, calcium channel blockers aren't as bad as people think
they are, and in some subclasses may be potentially beneficial,
with an emphasis on potential," Beattie said. "I don't
think people have sat down and qualitatively looked at the evidence
of cardiac surgery, and that's what this was an attempt to do."
Although Beattie said the meta-analysis results
were more persuasive than he had expected, he rated the quality
of the original studies as only poor to medium. Therefore, he concluded
that more work is needed before recommending changes in clinical
practice.
"The studies support the use of calcium
antagonists, as far as they go, but we didn't do this to change
management. If there is something in the meta-analysis, it really
has to be taken forward into a large, randomized, controlled trial.
And that's basically what we are trying to do now," he said.
The current study may help correct misperceptions about the potential
risks associated with calcium channel blockers, according to editorial
writer Lionel H. Opie, MD, FACC:
"Is the perception of harm correct? It largely came about in
1995 from studies when nifedipine capsules, that suddenly release
large amounts of the drug into the circulation, and are now hardly
ever used, were given in large doses to very seriously ill cardiac
patients when it was thought that coronary spasm was the main cause
of heart attacks. Rather, the nifedipine brought on heart attacks.
Bad news travels, good news does not."
Opie added, "Although a major contribution,
this meta-analysis does not clearly and unequivocally show that
calcium channel blockers confer benefits when given in association
with cardiac surgery. The authors are quite correct in emphasizing
that further prospective studies are needed to determine the true
effects of calcium channel blockers on outcome measures, particularly
including perioperative mortality. The specific message of the present
meta-analysis is quite clear: calcium channel blockers may be safer
and have more benefit in cardiac surgery than often supposed."
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