Aortic Dissection

Aortic dissection (AD) is a severe condition where a tear in the innermost layer of the aorta allows blood to flow between layers of the aortic wall, splitting them apart. This often results in sudden, severe chest or back pain, described as "tearing." Other symptoms may include vomiting, sweating, and lightheadedness.

AD can lead to life-threatening complications such as stroke, myocardial ischaemia, and aortic rupture.

Dissection of the descending part of the aorta

Signs and Symptoms

About 96% of individuals with AD experience severe, sudden-onset pain, often described as tearing, stabbing, or sharp. Pain location correlates with dissection location; anterior chest pain suggests ascending aorta involvement, while interscapular back pain hints at descending aortic dissections. Other symptoms can include congestive heart failure, fainting, stroke, and cardiac arrest. Blood pressure in AD cases is variable, often presenting as high in distal dissections and low in proximal ones due to complications like pericardial tamponade.

Diagnosis

Diagnosis involves a combination of medical history, physical examination, and imaging tests. Imaging techniques such as CT scan, MRI, and transesophageal echocardiogram (TEE) are very important for visualising the intimal flap and confirming AD. Chest X-rays may show a widened mediastinum or pleural effusions, although they are not definitive. D-dimer tests can help rule out AD if levels are below 500 ng/ml within 24 hours of symptom onset.

Aortic dissection on CXR: Note the wide aortic knob.

CT with contrast demonstrating aneurysmal dilation and a dissection of the ascending aorta (type A Stanford).

MRI of an aortic dissection: 1. Aorta descendens with dissection; 2. Aorta isthmus.

Classification

Two main classification systems are used: the DeBakey and Stanford systems. The DeBakey system categorises dissections based on the location and extent:

• Type I: Involves the ascending aorta, aortic arch, and often beyond.
• Type II: Confined to the ascending aorta.
• Type III: Involves the descending aorta and may extend distally.

The Stanford classification divides dissections into:

• Type A: Involves the ascending aorta and/or aortic arch, possibly extending to the descending aorta.
• Type B: Involves the descending aorta without affecting the ascending aorta.

DeBakey Type I Aortic Dissection.

Treatment

Management depends on the dissection type. Type A dissections usually require surgery, involving resection and grafting of the affected aorta. Type B dissections are typically managed medically, unless complicated by organ compromise or rupture, in which case surgical intervention is necessary. Blood pressure control is very important, with beta blockers being the first-line treatment. Surgical options include open aortic surgery, the Bentall procedure, and thoracic endovascular aortic repair (TEVAR).

Prognosis

Without treatment, type A dissections have a high mortality rate, with 75% dying within two weeks. Treatment improves survival rates significantly, with 30-day survival for thoracic dissections reaching up to 90%. Long-term management involves strict blood pressure control and regular imaging to monitor for new aneurysms or dissection complications.

Closure of the lumen of a Type B aortic dissection following medical management.

Self-assessment MCQs (single best answer)

Which symptom is most commonly associated with aortic dissection?

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What imaging technique is NOT typically used to diagnose aortic dissection?

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In the DeBakey classification system, which type involves the ascending aorta, aortic arch, and often beyond?

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What is the first-line treatment for blood pressure control in aortic dissection?

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What is a common finding on a chest X-ray of a patient with aortic dissection?

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Which classification system divides aortic dissections into Type A and Type B?

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What is the immediate treatment for a Type A aortic dissection?

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What complication is NOT typically associated with aortic dissection?

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Which location of pain suggests involvement of the descending aorta in aortic dissection?

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What is the primary goal in the long-term management of patients with aortic dissection?

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