Give beta-blockers after MI patients have stabilised
Use of early beta-blocker therapy in acute myocardial infarction reduces the risks of reinfarction and ventricular fibrillation, but increases the risk of cardiogenic shock, especially during the first day or so after admission to hospital, researchers have found (Lancet 2005;366:1622).
The COMMIT study (clopidogrel and metoprol in myocardial infarction trial)
allocated 45,852 patients admitted within 24 hours of suspected acute
myocardial infarction to receive either metoprolol — up to 15mg
intravenous then 200mg oral daily — or placebo (the study’s
two-by-two design also allowed patients to be allocated to either clopidogrel
or placebo).
Metoprolol was associated with a proportional reduction in reinfarction
and arrhythmia (464 versus 568 and 581 versus 698, respectively; both
P=0.001) and in the number of deaths attributed to arrhythmia (388 versus
498; P=0.0002). But it was associated with a proportional increase in
cardiogenic shock (1,141 versus 885; P<0.0001) and the number of deaths
attributed to cardiogenic shock (496 metoprolol versus 384 placebo; P=0.0002).
The absolute reduction in arrhythmia-related deaths and the absolute
increase in shock-related deaths were of similar magnitude, although
the risks and benefits emerged over different times scales — the
overall net effect of metoprolol therapy was adverse during the first
two days of treatment and beneficial thereafter.
“Given the excess of cardiogenic shock, immediate beta-blocker
therapy cannot be recommended routinely,” the authors conclude. “Instead,
it may generally be more prudent to start beta-blocker therapy only after
a patient’s haemodynamic condition has stabilised after MI, with
the aim of preventing reinfarction and sudden cardiac death during the
later period of the hospital stay.” |
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