triple rule-out computed tomography (CT) angiogram to image the coronary arteries, pulmonary vasculature, and the aorta
Educational Objective:
Put into practice the 2015 imaging guidelines for chest pain.
Key Point:
Sometimes patients present with such complex patterns that it is unsafe to pursue any one of the 3 classic life-threatening chest pain diagnoses (acute coronary syndrome, acute aortic syndrome, pulmonary embolism) at the exclusion of the others. In these cases, a new approach, the triple-rule out- CT angiogram, is recommended.
Explanation:
Patients who present to the ED with chest pain and a complex pattern of signs, symptoms, and clinical data (eg, difficult-to-interpret laboratory assessment, ECG findings) are traditionally placed into 1 of 3 diagnostic pathways for including/excluding 1 of 3 life-threatening problems:
- Acute coronary syndrome (ACS)
- Pulmonary embolism (PE)
- Acute aortic syndrome (AAS)
In this approach, an alternative pathway with additional imaging studies may be necessary if the initial, tentative diagnosis is unconfirmed. For this reason, such complex patients often undergo more than 1 imaging study to arrive at a diagnosis or to exclude all diagnoses considered to be life threatening.
The 2015 American Heart Association guidelines on imaging patients with chest pain in the ED recommend triple rule-out CT angiography in these patients to simultaneously evaluate for ACS, PE, and AAS in a single study. Initial, small, single-center studies have reported an negative predictive value between 99.4% and 100.0%, with both image quality and diagnostic accuracy being equivalent to the dedicated individual studies (coronary CT angiogram, CT pulmonary angiogram, and CT aortogram).
Triple rule-out CT angiography is obtained by starting with a coronary CT protocol and then imaging more of the chest (either from the aortic arch to the base or the entire chest) while using additional contrast to maintain pulmonary artery enhancement. This approach results in an increase in radiation dose from 25% to 150% and in contrast volume from 20% to 50%. For these reasons, dedicated CT imaging of the specific organ is still preferred over triple rule-out CT angiography when the differential diagnosis can be narrowed.
The guidelines state that triple rule-out CT angiography is appropriate when the overall likelihood of ACS, PE, or AAS is not low.
However, the increased diagnostic yield of triple rule-out CT angiography over dedicated coronary CT is quite small; therefore, triple rule-out CT angiography is rarely considered appropriate (coronary CT angiogram is preferable) when the overall likelihood of both PE and AAS is low.
Reference:
Rybicki FJ, Udelson JE, Peacock WF, et al. 2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain: a joint report of the American College of Radiology Appropriateness Criteria Committee and the American College of Cardiology Appropriate Use Criteria Task Force. J Am Coll Cardiol. 2016;67(7):853-879.
