Approach

Aortic dissection should be suspected when an abrupt onset of tearing or ripping chest, back or abdominal pain is reported.[10][11]​ Patients typically describe the pain as severe “sharp” or “stabbing”, maximal at onset.[4]​ Missing the diagnosis may be catastrophic, hence the importance of acute history taking to prompt further investigation.[11][27]

The usual presentation is a male patient in their 50s, but the condition may occur in younger patients who have Marfan syndrome, Ehlers-Danlos syndrome, or other connective-tissue disorders.[14][4]​ Other high-risk scenarios include a family history of aortic disease or connective-tissue disorder, known aortic disease or thoracic aortic aneurysm, and previous aortic manipulation (including cardiac surgery).[10][11] Most patients have prior hypertension, often poorly controlled.[10][11] Younger patients may have a connective-tissue disorder, or a recent history of heavy lifting or cocaine use. Because of the severity of the condition, the diagnosis should be considered in young patients, even when predisposing factors are absent.

Signs and symptoms

Acute onset of severe chest or back pain heralds acute aortic dissection in 80% to 90% of patients.[11] The pain associated with aortic dissection may be located retrosternally, interscapularly, or in the lower back.[10][14]​ Although the classic textbook description is of acute “tearing” or “ripping” pain, patients more commonly report the abrupt onset of severe “sharp” or “stabbing” pain, maximal at onset.[4]​ Anterior chest pain is typically associated with an ascending dissection; interscapular pain usually occurs with a descending dissection.[10][14]​ Pain may migrate through the thorax or abdomen, and the location of pain may change with time as the dissection extends.[10][14]​ A minority of patients present with syncope and no pain.[11]

It is important to recognize that no single symptom of aortic dissection is pathognomonic for the condition, as there is overlap with cardiac, pulmonary, abdominal, and musculoskeletal disorders.

Patients may be hemodynamically stable or in hypovolemic shock.[4]​ Blood pressure differences in the upper extremities or pulse deficits in the lower extremities should be sought.[10][4] A pulse deficit is particularly common in a proximal dissection affecting the aortic arch.[10][11]​ The deficit may be unilateral or bilateral depending on the level of the intimal flap.[10] A pulse deficit may also be present in more distal aortic dissections (e.g., of the descending aorta) and, in some cases, may lead to acute limb ischemia. However, pulse deficits are less common than in more proximal dissections.[10] A difference in systolic blood pressure of greater than 20 mmHg between the two arms is a key sign of aortic dissection.[4]​​​

Neurologic deficits may indicate involvement of cerebral or intercostal vessels. There may be depressed mental status, limb pain, paresthesia, weakness, or paraplegia. Symptoms of visceral ischemia may be present. Occasionally, a diastolic decrescendo murmur may be discovered, indicating aortic insufficiency. There may be symptoms or signs of heart failure, pericardial tamponade, or a left pleural effusion.[11] See Pleural effusion.

One systematic review identified neurologic deficit, hypotension, and a pulse deficit as the three clinical examination findings with the highest positive likelihood ratios for aortic dissection.[28]

Tests

The choice of investigations for diagnostic work-up of acute dissection is based on the patient’s hemodynamic status, likelihood of aortic dissection, and local availability and expertise.[10][4] Initial work-up includes ECG, and cardiac enzymes to exclude myocardial infarction.[4]​​[10][14]​ See ST-elevation myocardial infarction. 

Myocardial ischemia or infarction may be present in 10% to 15% of patients with aortic dissection, which can mask the diagnosis of dissection.[10]

Blood tests including a complete metabolic panel and complete blood count, including blood type and crossmatch, should also be requested. Despite a high sensitivity, D-dimer is not recommended as the sole screening tool for acute aortic dissection; while negative D-dimer may be helpful to rule out aortic dissection in low-risk patients, particularly when used within an integrated decision support tool, a positive D-dimer lacks specificity when used in isolation.[29][30]​ However, D-dimer will be of value when considering the differential diagnosis (e.g., pulmonary embolus).[27] Other biomarkers with the potential to assist in the diagnosis of aortic dissection include C-reactive protein, elastin degradation products, calponin, and smooth muscle myosin heavy chain, but none of these have been validated.[31]

In patients with a suspected aortic dissection, computed tomography angiography (CTA) is recommended for initial diagnostic imaging, given its wide availability, accuracy, and speed, as well as the extent of anatomic detail it provides.[4][24][10][11][14][32][33][34]​ CTA has a sensitivity greater than 90% and specificity greater than 85% for acute aortic syndromes, including aortic dissection.[10] CTA also shows the full extent of the dissection and, in some cases, the entry tear site. CTA can detect the presence and mechanism of aortic branch vessel involvement as well as vessel patency, signs of malperfusion, pericardial effusion and hemopericardium, periaortic or mediastinal hematoma, and pleural effusion.[4]​ For patients who cannot receive iodinated contrast, CT without contrast is an acceptable alternative. 

The diagnosis of aortic dissection is made by imaging an intimal flap separating 2 lumens. If the false lumen is completely thrombosed, central displacement of the intimal flap, calcification, or separation of intimal layers are definitive signs of aortic dissection. CTA also allows visualization of the extent of dissection and involvement of side branches.

A plain chest x-ray is neither sufficiently sensitive nor specific for aortic dissection to be used as a diagnostic tool. A chest x-ray may reveal other causes of acute chest pain.[4]​​[10][32][33][4]​​ Widening of the mediastinum or pleural effusion can indicate aortic dissection but is of limited diagnostic value, particularly if the dissection is confined to the ascending aorta; chest x-ray is normal in up to 40% of patients with aortic dissection.[11][14][34][35]

Transthoracic echocardiography (TTE) may be used in the emergency department, intensive care unit (ICU), or operating room for acute proximal dissections if the patient is clinically unstable and there is any question about the diagnosis, or if CTA is unavailable or contraindicated.[11][32][36][4]​ TTE can show pericardial effusion or aortic regurgitation, and a dissection flap can sometimes be visualized; however, more complete imaging of the aortic arch requires transesophageal echocardiography or CTA.[4]

For type A dissections (ascending), transesophageal echocardiography may be done in the ICU or operating room to confirm the diagnosis and better evaluate the aortic valve.[11] Sensitivity and specificity are higher than for TTE.

Magnetic resonance imaging (MRI) is most often used as a follow-up imaging modality in patients in which there is diagnostic uncertainty.[4]​ Magnetic resonance angiography is the most accurate, sensitive, and specific test for aortic dissection, but is rarely used in the acute setting because it is more difficult to obtain than CTA.[2][10]

In the setting of type B dissections (descending), if medical therapy fails and surgery is required, intraoperative intravascular ultrasound helps define the morphology of the dissection and assists in the treatment plan.

If the patient presents with an incidental finding of chronic dissection (such as mediastinal widening or prominent aortic knob on chest x-ray), diagnosis is confirmed by cross-sectional imaging such as CTA, TTE, or MRI.[24][10][Figure caption and citation for the preceding image starts]: Transesophageal echocardiography (transverse aortic section) showing a circumferential dissection of the ascending aorta in a 30-year-old patient with features of Marfan syndromeBouzas-Mosquera A, Solla-Buceta M, Fojón-Polanco S. Circumferential aortic dissection. BMJ Case Reports 2009; doi:10.1136/bcr.2007.049908 [Citation ends].com.bmj.content.model.Caption@77778af9[Figure caption and citation for the preceding image starts]: CT scan showing dissecting aneurysm in a 45-year-old patient with Marfan syndrome experiencing chest painSanyal K, Sabanathan K. Chest pain in Marfan syndrome. BMJ Case Reports 2009; doi:10.1136/bcr.07.2008.0431 [Citation ends].com.bmj.content.model.Caption@1729c217[Figure caption and citation for the preceding image starts]: 3D CT, distal dissectionFrom the collection of Dr Eric E. Roselli; used with permission [Citation ends].com.bmj.content.model.Caption@998f322[Figure caption and citation for the preceding image starts]: CT of a 71-year-old man showing type II dissecting aneurysm of the ascending aorta. Hematoma around the proximal segment of the ascending aorta (panels A-D) compressed the right pulmonary artery, almost occluding its patency and limiting the perfusion of the reciprocal lungStougiannos PN, Mytas DZ, Pyrgakis VN. The changing faces of aortic dissection: an unusual presentation mimicking pulmonary embolism. BMJ Case Reports 2009; doi:10.1136/bcr.2006.104414 [Citation ends].com.bmj.content.model.Caption@2a827031

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