[Prognostic significance of ST segment change in acute myocardial infarct].

The extent of ST segment elevation resolution (STR) 180 minutes after initiation of streptokinase treatment for acute myocardial infarction within 6 hours after onset of symptoms is an excellent early prognostic indicator that can be easily determined in all patients. This presentation is based on a meta-analysis from 3 thrombolysis studies including 3,912 patients. About 50% of patients had complete STR (> or = 70%). They had small enzymatic infarct sizes and well preserved left ventricular function associated with an excellent chance of survival. Patients with partial STR (< 70 to 30%) developed larger infarcts, but had still a relatively low mortality. To assess the optimal cut-off point that best predicts an increased mortality risk, the squared standardized log odds ratio statistics as a function of the hypothetical cut-off points in STR was used. A cut-off point around 30% STR was associated with an extraordinarily strong predictive power. The 35-day cardiac mortality with STR < 30% was 12.7% as compared to 2.1% for patients who had complete STR and 4.2% for those who had partial STR. Based on STR, age, medical history, and simple parameters at admission, a low risk population can be defined that includes about 50% of all patients aged < or = 70 years, and 20% of older patients. The 35-day and 1-year mortality rates for the group of younger patients was 1.4% and 2.7%, respectively, and for the older age group 5.0% and 7.9%. It appears highly unlikely that aggressive testing and interventions would have any measurable beneficial effect on such a good outcome. In thrombolytic therapy comparative trials STR may perform well as a surrogate endpoint, since it is more powerful than 90 minutes post-thrombolytic patency rates and early mortality, in a statistical sense. This is especially true for Phase-II dose-finding studies and the use as a surrogate or even primary endpoint in phase-III trials. In addition, STR may be very helpful for safety monitoring, interim analyses, and subgroup analyses in megatrials with the endpoint mortality. Use of STR can result in a substantial reduction in the required sample size. However, at least 1 pivotal mortality trial cannot be replaced by STR trials, since STR does not reflect the risk of intracranial hemorrhages and other bleeding complications.