The Diagnosis of acute coronary syndrome in patients presenting with acute chest pain is problematic when both, electrocardiogram and serum troponins are normal. Multidetector row computed tomography angiography (CTA) allows direct and rapid non-invasive visualization of coronary artery disease.

The investigator's aim is to assess the diagnostic accuracy and safety of a novel diagnostic strategy based on MDCT as compared to a strategy using stress echocardiography in the workup of patient with chest pain, normal electrocardiogram, normal troponins and suspected coronary artery disease. Additionally, the cost associated with both strategies will be compared.

Methods. A total of 150 patients with acute chest pain coming to the emergency room with intermediate probability of significant coronary artery disease, normal ECG and troponins will be prospectively randomized to MDCT or stress echocardiography with exercise. Patients showing coronary stenosis >50% at MDCT or abnormal stress echocardiography or inconclusive results will be admitted for further study. The primary endpoint of the study is the detection of an acute coronary syndrome, defined as typical or atypical angina with documented significant coronary artery disease (>50% stenosis) on invasive coronariography, a positive stress test or the occurrence of cardiac death, myocardial infarction or need for revascularization during 6 month follow-up. All MDCT angiograms and echocardiograms will be evaluated by an experienced radiologist and cardiologist.

Design and Aim: This is a prospective pilot study to evaluate the role of multidetector row computed tomography angiography (CTA) to rule out Acute Coronary Syndrome among patients presenting to the ER with chest pain complaints, non-diagnostic ECG and normal troponins and intermediate pre-test probability for significant CAD.

Methods: Following the initial clinical evaluation and the results of initial ECG, blood test and X-ray, patients meeting the inclusion criteria will be randomized to undergo either a CTA scan or a Exercise Stress Echocardiogram to rule out significant coronary artery disease.

CTA will be carried out in a 64 or 128 slice-CT Scanner (SIEMENS,Somaton Sensation 64 or 128-Flash Definition)following iv administration of iodinated contrast (bolus: 5cc x acquisition time (seg)+ 10 cc). Images will be interpreted by two experienced physicians (radiologist and cardiologist)

Stress Echocardiography will be performed and interpreted by an experienced Echocardiographer (cardiologist).

Clinical decision making: Patients with a positive or inconclusive test in each arm will be admitted to the hospital for treatment or further additional testing, while patients with negative results will be discharged from the ER.

Safety issues: A phone call and chart review will be performed one month and 6 months follow-up to register the occurrence of any major adverse cardiac events, as well as new consultation for chest pain.

Inclusion Criteria:

• Patient is in Sinus Rhythm
• Typical or atypical chest pain lasting more than 5 min in the last 24 hs.
• Estimated pre-test probability of significant coronary artery disease more than 15%.
• Absence of ECG changes suggestive of myocardial ischemia (ST-segment deviation >1 mm or T Wave inversion > 4 mm in at least two contiguous leads).
• Negative initial troponins I at admission (<0.05 ng/ml)

Exclusion Criteria:

• Known allergy to iodinated contrast.
• Known renal insufficiency or Creatinine >1.5 mg/dl at admission.
• History of known coronary artery disease or prior myocardial revascularization
• Any of the following:hemodynamic instability, persistent chest pain despite treatment, Systolic blood pressure <100 mm Hg.
• Cardiac arrhythmia with rapid or irregular ventricular response.
• Inability to perform an exercise test.
• Patient is incapable of providing informed consent.