Once a clinician decides to evaluate a patient for thoracic aortic dissection, imaging and diagnostic tests must be selected. In recent years, there has been a great deal of literature published on the use of D-dimer in the evaluation of aortic dissection. However, the low quality of these studies resulted in a Level C recommendation for the use of D-dimer to rule out dissection.

Critical Question 3

In adult patients with suspected acute nontraumatic thoracic aortic dissection, is the diagnostic accuracy of a computed tomography angiogram (CTA) at least equivalent to that of transesophageal echocardiogram (TEE) or magnetic resonance angiogram (MRA) to exclude the diagnosis of thoracic aortic dissection?

In the ED, CTA is often used to evaluate patients for suspected thoracic aortic dissection. The Class I, II, and III studies identified in the systematic review of the diagnostic accuracy of CTA reported sensitivities ranging from 93 percent to 100 percent. The evidence demonstrated that the sensitivity of CTA is very similar to that of TEE and MRA, diagnostic modalities that have been suggested as useful for the evaluation of an aortic dissection. CTA is often more readily available in the ED than TEE and MRA, which makes it a practical diagnostic tool. As such, its use received a Level B recommendation.

Critical Question 4

In adult patients with suspected acute nontraumatic thoracic aortic dissection, does an abnormal bedside transthoracic echocardiogram establish the diagnosis of thoracic aortic dissection?

A bedside ultrasound exam such as a transthoracic echocardiogram (TTE) to rule out acute nontraumatic thoracic aortic dissection would be very useful and is becoming a tool in the ED physicians’ diagnostic algorithm as our skills in ultrasound have evolved. However, there are no current studies evaluating ED physician–performed TTE in ruling out thoracic aortic dissection.

The Level B recommendation was, in adult patients with suspected nontraumatic thoracic aortic dissection, do not rely on an abnormal bedside TTE result to definitively establish the diagnosis of thoracic aortic dissection. The Level C (consensus) recommendation was, in adult patients with suspected nontraumatic thoracic aortic dissection, immediate surgical consultation or transfer to a higher level of care should be considered if a TTE is suggestive of aortic dissection.

Critical Question 5

In adult patients with acute nontraumatic thoracic aortic dissection, does targeted heart rate and blood pressure lowering reduce morbidity or mortality?

Once a diagnosis is made, treatment is initiated with the aim of reducing heart rate and blood pressure. Existing guidelines generally recommend aiming for targets of 60 beats/minute and systolic blood pressure below 120 mm Hg. However, there are currently no prospective human trials that demonstrate the superiority of a strategy of decreasing heart rate prior to reducing blood pressure. There is insufficient evidence to definitively identify an optimal target in all patients regardless of age and comorbidities. The Level C recommendation is, in adult patients with acute nontraumatic thoracic aortic dissection, decrease blood pressure and pulse if elevated. However, there are no specific targets that have demonstrated a reduction in morbidity and mortality.