Studies have shown that the time period in which thrombolytic therapy is effective after myocardial infarction (MI) is short. After 12 hours, it's no longer effective and may even be harmful. However, in the wake of recent studies suggesting that some myocardial tissue may be viable even after such a long postinfarct period, researchers in Germany investigated whether mechanical reperfusion is a good alternative to the conservative treatment currently recommended, and the results are promising.
Researchers enrolled 365 patients in the study, all of whom arrived between 12 and 48 hours after the first signs of a heart attack (and all of whom had documented ST-segment elevation MI); all were given standard anticoagulative and antiplatelet therapy. They were randomized to receive either conservative treatment (IV infusion of unfractionated heparin or subcutaneous low-molecular-weight heparin for at least a day; n = 183) or invasive treatment (n = 182), most often (87%) stent placement with adjunctive antiplatelet therapy with abciximab. (Other procedures performed were balloon angioplasty [7%] and aortocoronary bypass graft surgery [4%]; three patients received no intervention).
The primary outcome was final infarct size, as determined by computed tomographic scanning. Secondary outcomes were death from all causes, recurrent MI, and stroke within 30 days.
The mean final left ventricular infarct size in the invasive-treatment group was 11.6%, significantly smaller than the 18.4% seen in the conservative-treatment group. Results were also better in patients who underwent invasive treatment when various subgroups were compared, including patients presenting with a first infarction, those presenting 12 to 24 hours after first symptoms, those presenting 24 to 48 hours after first symptoms, and so on.
At the 30-day follow-up, three patients in the invasive-treatment group had died, compared with seven in the conservative-treatment group. Five in the invasive-treatment group had a second MI, compared with eight in the conservative-treatment group. Only one patient (in the conservative-treatment group) suffered a stroke. There were more episodes of major bleeding in the invasive-treatment group than in the control group (six versus two, respectively), as well as episodes of serious thrombocytopenia (two versus none, respectively). Results were comparable at 90 days, as well. The authors say their findings show that any viable myocardium present 12 hours or longer after an MI "may be salvaged if an effective reperfusion strategy is applied."-Doug Brandt
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Schomig A, et al. JAMA 2005;293(23): 2865-72.