 The data will be analyzed with a cohort study design, calculating odds ratios between ECG characteristics and outcomes. The two primary ECG characteristics investigated will be 1 presence of at least 2 consecutive leads with at least a partially concordant T-wave biphasic or entirely concordant, and 2 the STS ratio the ratio of the ST-segment deviation to the S or R wave amplitude, whichever greater. Secondary ECG features measured will include heart rate, rhythm, intervals, bundle branch blocks, PR and ST segment deviations and concordancediscordance, PQRST amplitudes, QRS durations, QT intervals, T wave inversions, segment contours and concavityconvexity. The primary outcomes of interest will be 1 positive cardiac troponin T biomarker levels on index visit, and 2 positive stress test results on index visit. Secondary outcomes will include the rates of 30-day myocardial infarction, 30-day death, and 30-day revascularization. 