Estimated appearance of raised serum enzyme activity in relation to onset of symptoms in acute myocardial infarction.

In 709 patients with definite acute myocardial infarction (MI) the appearance of raised serum enzyme activity was related to onset of symptoms. Heat stable lactate dehydrogenase (LD), creatine kinase (CK) and CK B were analysed. A gradual increase in the incidence of raised enzyme activity in the first blood sample was seen for up to 18 hours after the onset of MI for all 3 enzymes. The incidence of raised enzyme activity in the first blood sample was higher for CK and CK B than for heat stable LD up to 24 hours after onset of MI, but thereafter a similar incidence was found. The median time between onset of symptoms and estimated appearance of raised serum enzyme activity was 6.2 hours for heat stable LD versus 4.3 hours for CK and 4.1 hours for CK B. A wide variation was however found. Infarct localization and chronic treatment with betablockade might affect these results. The clinical course including short- and long-term survival was similar in patients with early and later appearance of enzymes.