Göteborg Metoprolol Trial: enzyme-estimated infarct size.

In 1,375 patients serum activity of heat-stable lactate dehydrogenase (LD; E.C.1.1.1.27.) was analyzed every twelfth hour for 48 to 108 hours. The mean maximum LD activity was 11.1 +/- 0.4 mu kat X 1(-1) in the metoprolol group vs 12.4 +/- 0.5 mu kat X 1(-1) in the placebo group (p = 0.054). In patients in whom treatment was started 12 hours or less after the onset of pain, a 17% reduction in LD activity was observed (p = 0.009) and similar results were found in patients randomized 8 hours or less. Groups in which the effect after metoprolol treatment was more pronounced were those with an initially higher heart rate and also those with anterior myocardial infarction.