Cardiology>>>>>Aorta And Hypertension
Question 9#

Which one of the following statements regarding the choice of imaging in a patient with suspected acute type A aortic dissection is true?

A. A transthoracic echocardiogram is the first investigation of choice because of its availability and accuracy/ease of use/ability to assess the aorta and left ventricular function
B. A plain chest radiograph with non-mediastinal widening is a typical finding in 50% of patients with aortic dissection
C. A disadvantage of TOE is that part of the ascending aorta is obscured by the trachea
D. Absence of ECG gating prevents accurate diagnosis of type A dissection in 35% of patients
E. The presence of a Medtronic Surescan DDDR device is a good reason not to opt for MRI of the aorta

Correct Answer is C

Comment:

Distal segments of the ascending aorta may not be well seen with TOE as the trachea and left main bronchus pass between the oesophagus and the aorta. TTE has a role in the acute setting but the sensitivity and specificity for accurate diagnosis remain low. Routine chest radiographs are abnormal in 56% of patients with suspected aortic dissection. The sensitivity and specificity of the accuracy of CXR in acute aortic syndromes are 64% and 86%, respectively. These fall when pathology is confined to the ascending aorta. However, a completely normal chest radiograph reduces the likelihood of aortic dissection. In patients with aortic aneurysms, distinguishing a tortuous aorta from an aneurysm is difficult. CT of the aorta is rapidly becoming the investigation of choice for diagnosing acute aortic dissection because of its availability and ease of use. ECG gating can help eliminate false-positive results (e.g. where an intimal flap is mistaken for pulsation artefact). As technology improves, one may anticipate accurate assessment of coronary involvement. Assessment of the aorta with MRI tends to be reserved for follow-up studies because of the time taken for the study. The Surescan device is an MRI-safe pacemaker.