CT Triple-rule out is an ECG gated multi detector computerized tomographic scan which can be used in for patients presenting to the emergency department with acute chest pain. Three important potential causes: aortic dissection, pulmonary embolism and coronary artery disease constitute the ‘triple’ rule out. It can be done rapidly in potentially life threatening chest pain cases of acute chest pain and has high negative predictive value . A potential chance for misdiagnosis of aortic dissection with CT is the pulsation artefact due to movement of ascending aorta due to cardiac contraction . It has been successfully eliminated by ECG gating and certain reconstruction algorithms. Other potential errors causing misdiagnosis of aortic dissection are the presence mediastinal clips and indwelling catheters. Contrast enhancement of adjacent superior vena cava can also occasionally be misleading. This has been taken care of by adjustment of volume of iodinated radiocontrast injected and the rate of injection. Though CT triple rule out is useful for assessing proximal coronaries, it is not as good as conventional coronary angiogram to visualise the details of the coronary anatomy. In visualising details of coronary anatomy, standard CT coronary angiogram is also superior to CT triple rule out. Significant pulmonary embolism can very well be picked up by CT triple rule out.
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