What is the triple rule out (TRO) for cardiac assessment?

Updated: Nov 20, 2018
  • Author: Richard S Krause, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

Conceptually, a CT scan with intravenous (IV) contrast can combine imaging of the coronary arteries, ascending aorta, and pulmonary arteries; this allows assessment of coronary artery disease (CAD), pulmonary embolism, and disease of the thoracic aorta (dissection) with a single study. This type of evaluation has been called the "triple rule out (TRO)." Technical aspects of this type of study differ from that of CCTA, owing to a wider field of view and a different protocol for the administration of IV contrast. The technique involves substantial cost and radiation exposure. 

A review of TRO suggests that this approach may have utility under relatively limited circumstances. [38]  In a 2013 study that evaluated 100 intermediate-risk patients with acute chest pain and an intermediate risk for acute cornary syndrome, coronary CT angiography (CCTA) and TRO-CTA both allowed the rapid and safe discharge of a majority of these patients as well as identified those wth significant coronary artery stenosis. [37] All patients had D-dimer testing; those with positive results were imaged with either a TRO protocol or with CCTA. Of the 60 of 100 discharged with a negative CCTA, 0 adverse events occurred at 90-day follow-up; of the 19 of 100 with a positive CCTA, 17 were determined to be true positives based on catheter angiography. Thirty-six patients underwent a TRO-CCTA protocol due to elevated D-dimer levels: 5 had pulmonary embolism, 3 had pleural effusion of unknown etiology, and 1 each had severe right-sided ventricular dysfunction with pericardial effusion or an incidentally detected bronchial carcinoma. [39]

In current practice, TRO-CTA exposes patients to significant radiation but shows promise in appropriately selected patients. Improved scanning hardware and imaging algorithms have the potential to reduce radiation exposure without compromising accuracy. To date, no consensus has been reached as to which patients are most appropriate for TRO imaging.


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