This is a prospective, randomized multicenter trial comparing MSCT to standard of care (SOC) diagnostic treatment in the triage of Emergency Department (ED) low to intermediate risk chest pain patients. Our hypotheses are that compared to SOC treatment, MSCT is equally safe and diagnostically effective, as well as more time and cost efficient.

Computed tomography (CT) or "cat scan" is an x-ray test routinely used for diagnostic purposes. Heart ("Cardiac") CT, using the newest scanners, is an improved way of looking at the coronary arteries, which supply blood to the heart muscle. If these arteries are clogged this may cause chest pain or even a heart attack. The images of the coronary arteries obtained by CT scanners (during a 5-10 minute procedure) have been shown by many studies to be accurate, when compared to the conventional invasive cardiac catheterization procedure. In addition, at least five prior studies done at different hospitals suggest that cardiac CT scans are effective for diagnosing chest pain like yours in patients coming to the emergency room. What is new about this study is that it is being done in multiple hospitals at the same time. This is part of the process that all medical advances must go through to become a part of routine care of patients in hospitals throughout the country.

A standard chest pain workup typically done in the emergency department consists of a physical examination, electrocardiograms (EKGs), and several blood tests. Blood tests typically completed include cardiac enzymes (Troponin, CK & CK-MB), a kidney function test, a pregnancy test if applicable, and possibly a lipid panel, depending on physician preference. For each test, a 3mL vial will be filled with a specimen of blood and processed in the laboratory for result. Also a two-part "rest-stress" nuclear scan is typically performed, which compares blood flow into the heart tissue at rest to blood flow into the heart tissue during exercise or dilation with medications. Based on prior studies, the researchers doing the present study believe that CT scanning of the coronary arteries can provide information that is just as safe and accurate as the rest-stress nuclear scan, and can do so more rapidly at a lower cost.

Inclusion Criteria:

• Chest pain or anginal equivalent symptoms suggestive of acute coronary ischemia within the past 12 hours.
• TIMI risk score less than or equal to 4.
• Ability to provide informed consent.
• Age greater than or equal to 25 years.

Exclusion Criteria:

• Attending physician makes clinical decision for immediate invasive evaluation.
• Electrographic evidence of ischemia, including acute Non ST-Elevation Myocardial Infarction (NSTEMI) or ST-Elevation Myocardial Infarction (STEMI), with ST segment elevation or depression equal to or greater than 1mm in two or more contiguous leads, and/or T wave inversion greater than or equal to 2 mm.
• Positive cardiac biomarkers (troponin, CK, and/or CK-MB) compatible with AMI on initial laboratory testing, based on site standard laboratory values.
• Presence of pre-existing CAD, including prior MI, prior angiographic evidence of significant CAD, defined as greater than or equal to 25% stenosis, or history of coronary artery bypass graft (CABG) surgery.
• Renal insufficiency (creatinine greater than 1.5 mg/dL) or renal failure requiring dialysis.
• Atrial fibrillation or other markedly irregular rhythm.
• Psychological unsuitability or extreme claustrophobia.
• Pregnancy or unknown pregnancy status.
• Clinical instability including cardiogenic shock, hypotension (systolic blood pressure <90 mmHg), refractory hypertension (systolic blood pressure >180 mmHg on therapy), sustained ventricular or atrial arrhythmia requiring intravenous medications.
• Known allergy to iodine or iodinated contrast.
• Inability to tolerate beta-blocker medication, including patients with asthma or chronic obstructive pulmonary disease (COPD) requiring maintenance, i.e. use of inhaled bronchodilators or steroids, or patients with complete heart block or second-degree atrioventricular block.
• Iodinated contrast administration or x-ray scan within the past 48 hours.
• Use of any erectile dysfunction medications such as Viagra or Cialis in the last 24 hours.
• Body Mass Index (BMI) greater than or equal to 39 kg/m2. . Use of biguanides within the past 48 hours