New Non-invasive Method to Detect Myocardial Ischemia-The timely diagnosis of patients suspected of having Acute Coronary Syndromes (acute myocardial infarction or unstable angina) is crucial to favorable short- and long-term patient outcomes. The conventional 12-lead electrocardiogram (ECG) is the primary diagnostic tool for the detection of Acute Coronary Syndromes (ACS) in patients presenting to the Emergency Department (ED) with chest pain or anginal equivalents. Unfortunately, the conventional ECG lacks sensitivity to diagnose approximately 50% of these patients. The purposed research examines a promising new non-invasive method of ischemia detection which could improve the diagnostic yield of the electrocardiogram. Digital signal processing techniques are used to uncover subtle, high frequency, low amplitude, components of the ECG depolarization wave (HF-QRS). Studies show that HF-QRS component detection may improve the sensitivity and specificity of ischemia detection by as much as 5-15%. A secondary analysis of high resolution, 24-hour Holter data from a prospective clinical trial will be conducted to compare sensitivity and specificity of conventional ECG versus HF-QRS in the detection of ischemia. [unreadable] [unreadable] [unreadable]