In recent years, a large number of studies have been conducted on how to improve the treatment of patients in the Emergency Room (ER) complaining of chest pains. Great advances have been achieved recently regarding diagnostic methods aided by coronary CT angiopraphy (CCTA) and sensitive troponins. However, various questions about these methods still remain obscure and there is no effective comparison between them in patients with intermediate risk. The aim of the study is to evaluate the sensitivity and specificity of sensitivity troponins in the detection of coronary artery disease in patients with chest pain and the intermediate probability of ACS compared with CCTA.

This will be a prospective and unicentric study with approximately 200 subjects recruited over a planned recruitment period of 24 months. Based on an alpha error of 0.05 and using a power of 0.8 for the primary outcomes, investigators calculated the number of individuals necessary for the study to be at least 141. All patients will be submmited to troponin measurements and CCTA. The commercial kit ADVIA Centaur® TnI-Ultra (Siemens Healthcare Diagnostics, Tarrytown, NY, USA) is used for this in automated equipment of the same brand. It is measured at the central InCor laboratory. The 99th percentile value is 0.04 ng/ml. The CCTA used will be the 320-channel Toshiba Aquilium machine. If the CCTA result shows coronary stenosis greater than or equal to 50%, the patient will initiate the ACS treatment and be hospitalized to have coronary cineangiography. In case the CCTA shows lesions of less than 50%, the patient will be discharged and monitored for 30 days by telephone. This conduct is already followed as a routine in the emergency unit at InCor for both situations. A second sampling of the troponin kit will be obtained from all patients three hours after the first collection in order to evaluate for an increase/decrease of troponin. This second troponin measurement, however, it is blinded to the main investigator, who will only have access to it after the evaluation of outcomes at the end of the study. All the data will be placed in a Microsoft Access database table and analyzed with the SAS Statview 5.0 software. The comparative analysis between the methods will be made using the area under the ROC curve and obtaining sensitivity, specificity, positive and negative predictive values, and accuracy.

Inclusion Criteria:

• chest pain for at least two hours before arriving at the emergency unit
• non-diagnostic electrocardiogram (absence of new or probable deviation of ST of at least 0.5 mV and/or T wave inversion of at least 0.2 mV)
• TIMI risk of 3 or 4
• first measurement of troponin I less than or equal to ≤ 0.03 ng/ml
• informed consent form signed.

Exclusion Criteria:

• pregnancy
• hemodynamic instability (pulmonary congestion / systolic arterial pressure lower than 90 mmHg)
• serum creatinine higher than 1.5 mg/dL
• intolerance to ß-blockers
• allergy to iodinated contrast
• asthma
• thoracic trauma within the last 30 days
• body mass index greater than 40 kg/ m2
• previous surgical myocardial revascularization
• other identified causes of troponin increase