The purpose of this project is to examine the effectiveness of computed tomographic angiography (CTA) in patients with non-ST elevation acute coronary syndrome (NSTE-ACS). People who are hospitalized with this situation often require an angiogram to assess the heart and its arteries.

Recent advancements in technology have enabled CTA to clearly define coronary artery anatomy with great accuracy and to guide treatment strategies in select patient populations. We are investigating that CTA may be used, as an alternative to conventional angiograms, for the risk stratification of patients with high risk NSTE-ACS.

Patients eligible for the study will be high risk NSTE-ACS and awaiting an angiogram. Enrolled patients will undergo CTA prior to the angiogram. With each CTA the patient will be injected with a small dose of an X-ray dye and will be asked to lie still on the "scanning bed" for a period of 5-10 minutes.

Inclusion Criteria:

• High risk ACS

  1. Angina [accelerating pattern or prolonged episode (> 20 minutes) or recurrent episode at rest or with minimal effort within preceding 24 hours]; and (13)
  2. Elevated Troponin - T (≥0.1 ug/L) or ECG changes consistent with ischemia [ST depression ≥ 0.1 mV, transient ST segment elevation ≥ 0.1 mV (< 20 minutes)]) (11;13)

• Planned conventional invasive coronary angiography

Exclusion Criteria:

• Age < 18 years or lack of consent
• Renal Insufficiency (GFR < 60 ml/min)
• Allergy to contrast agent
• Refractory angina requiring urgent/emergent coronary angiography (as per treating physician)
• Contraindication to radiation exposure (e.g. pregnancy)
• Uncontrolled HR
• Previous CABG or PCI/Stent
• Atrial fibrillation, frequent atrial or ventricular ectopy (> 1 / minute)
• Unable to perform 20 second breath-hold