In a recent issue of The American Journal of Cardiology , Kumar et al compared the predictive efficacy of 2 different time points for assessment of ST-segment resolution after primary percutaneous coronary intervention for ST elevation myocardial infarction. They found that complete (≥70%) ST-segment recovery immediately succeeding primary percutaneous coronary intervention defined a lower risk population than similar ST-segment recovery at 90 minutes and that assessment at 90 minutes was less useful for discrimination of risk. On the basis of their results, the investigators concluded that early assessment confers a predictive advantage over assessment at 90 minutes.

Given that most patients who undergo primary percutaneous coronary intervention enjoy a favorable prognosis, it seems to us that the clinical utility of ST-segment assessment after mechanical reperfusion lies mainly in helping define high-risk patients to ensure appropriate therapeutic interventions at an early time point. In the design of their study, Kumar et al do not seem to have placed much importance on this issue. Some additional analyses might have been very useful to address this question. A first step would have been to go beyond the crude dichotomized measure of ST-segment resolution and explore the prognostic implications of more refined categorizations, so that further risk stratification of those patients with lack of immediate ST-segment recovery had been achieved.

Other analyses would also have been instructive. For instance, absolute measures of residual ST-segment elevation or deviation perform at least as well for partitioning of risk as the more complex algorithm evaluated by Kumar et al and might perform even better at later time points (e.g., 60 or 90 minutes). However, it is more likely that the optimal time point for electrocardiographically guided identification of high-risk patients lies somewhere between 0 and 90 minutes. To address this question, we need data from a comprehensive assessment of other time points within this 90-minute interval. Finally, continuous ST-segment monitoring, if available, is the preferred method for ischemia surveillance and electrocardiographic risk stratification in acute coronary syndromes.