Impact of prediction of outcome by early ST segment changes in acute myocardial infarction

The extent of ST segment elevation resolution (STR) 180 minutes after initi ation of streptokinase treatment for acute myocardial infarction within 6 h ours after onset of symptoms is an excellent early prognostic indicator tha t can be easily determined in all patients. This presentation is based on a meta-analysis from 3 thrombolysis studies including 3 912 patients. About 5045 of patients had complete STR (greater than or equal to 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 mor tality. To assess the optimal cut-off point that best predicts an increased mortality risk, the squared standardized log odds ratio statistics as a fu nction of the hypothetical cut-off points in STR was used. A cut-off point around 30% STR was associated with an extraordinarily strong predictive pow er. 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 l ow risk population can be defined that includes about 50% of all patients a ged < 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, an d for the older age group 5.0% and 7.9%. It appears highly unlikely that ag gressive testing and interventions would have any measurable beneficial eff ect on such a good outcome. In thrombolytic therapy comparative trials STR may perform well as a surrog ate endpoint since it is more powerful than 90 minutes post-thrombolytic pa tency 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 megatrial s with the endpoint mortality. Use of STR can result in a substantial reduc tion in the required sample size. However, at least I pivotal mortality tri al cannot be replaced by STR trials, since STR does not reflect the risk of intracranial hemorrhages and other bleeding complications.