ST-segment depression in non–ST elevation acute coronary syndromes: Quantitative analysis may not provide incremental prognostic value beyond comprehensive risk stratification

Background It is unclear whether quantitative ST-segment assessment can improve risk stratification of unselected acute coronary syndrome (ACS) patients using the validated Global Registry of Acute Cardiac Events (GRACE) risk model. Methods In the prospective, multicenter, Canadian ACS Registry, the admission electrocardiogram was evaluated centrally at a blinded core laboratory. Patients with ST-elevation myocardial infarction and other electrocardiogram confounders were excluded. ST depression (ST↓) was measured and summed in all leads except aVR. Patients with ST↓ were divided into 3 groups based on tertiles of cumulative ST↓. A multivariable model was developed to examine the independent prognostic value of ST↓ severity after adjusting for other known prognosticators in the GRACE risk model. Results Among 2590 patients with non–ST-elevation ACS, more severe ST↓ was associated with advanced age, higher heart rate and Killip class, elevated creatinine, abnormal biomarkers, higher GRACE risk score, and higher 1-year mortality (all P < .001). After adjusting for these confounding prognosticators, the presence of any ST↓ remained independently associated with higher 1-year mortality (odds ratio 1.78, 95% CI 1.21-2.63, P = .004). However, the gradient of risk with increasing magnitude of ST↓ was no longer evident (adjusted odds ratios 1.77, 1.77, 1.81, for ascending tertiles of cumulative ST↓, respectively). Moreover, quantitative ST↓ did not improve the model discrimination for 1-year mortality. The results were similar when the number of leads with ST↓ or the maximum magnitude of ST↓ was analyzed, after adjusting for tertiles of GRACE risk score or inhospital revascularization, or using the composite end point of death or myocardial (re)infarction at 1 year. Conclusions Greater ST↓ is associated with other adverse prognosticators across the broad spectrum of non–ST-elevation ACS. Although the presence of any ST↓ is an independent predictor of 1-year mortality, its quantitative assessment is not as important as its mere presence when studied on the background of comprehensive clinical and biomarker evaluation in a nonclinical trial–based ACS population.