Aortic Dissection: Causes, Symptoms and Treatment

Aortic Dissection is a condition where a tear in the aortic intima allows blood to surge into the aortic wall, causing a split between the inner and outer tunica media, and creating a false lumen.

Causes

Degenerative changes in the smooth muscle of the aortic media are the predisposing event.

Common causes and predisposing factors are:

hypertension;

Aortic atherosclerosis.

Connective tissue diseases.

Congenital cardiac abnormalities such as coarctation of aorta.

Aortitis (e.g. Takayasu's aortitis, tertiary syphilis).

Iatrogenic (e.g. during angiography or angioplasty.

Trauma.

Crack cocaine.

Stanford classification divides dissection into:

Type A: with ascending aorta tear (most common);
Type B: with descending aorta tear distal to the left subclavian artery.

Expansion of the false aneurysm may obstruct the subclavian, carotid, coeliac and renal arteries.

Epidemiology

Most common in ♂ between 40 and 60 years.

Clinical features

History

Sudden central ‘tearing’ pain, may radiate to the back (may mimic an MI).

Aortic dissection can lead to occlusion of the aorta and its branches:

Carotid obstruction: Hemiparesis, dysphasia, blackout.

Coronary artery obstruction: Chest pain (angina or MI).

Subclavian obstruction: Ataxia, loss of consciousness.

Anterior spinal artery: Paraplegia.

Coeliac obstruction: Severe abdominal pain (ischaemic bowel).

Renal artery obstruction: Anuria, renal failure.

Examination

Murmur on the back below left scapula, descending to the abdomen.

Blood pressure (BP): Hypertension (BP discrepancy between arms of >20 mmHg),

Wide pulse pressure.

If hypotensive may signify tamponade, check for pulses paradoxus.

Aortic insufficiency: Collapsing pulse, early diastolic murmur over the aortic area.

Unequal arm pulses.

There may be a palpable abdominal mass.

Diagnostic Investigations

Blood tests required include;

Full Blood Count,

Grouping and cross-match 10 units of blood,

Urea and electrolyte levels

Renal function tests,

Coagulation profile.

Imaging such as a Chest X-Ray may indicate a widened mediastinum and a localized bulge in the aortic arch.

An electrocardiogram is often normal but in some cases, it may show signs of left ventricular hypertrophy or inferior myocardial infarction if dissection compromises the Ostia of the right coronary artery.

CT-scan of the thorax may show a false lumen of dissection.

Transoesophageal echocardiography is highly specific.

Cardiac catheterization and aortography are also important in diagnosis.

Management

When an acute aortic dissection is suspected, a CT scan of the thorax should be performed urgently concurrent with resuscitation.

Resuscitate and restore blood volume with blood products.

Monitor pulse and blood pressure in both arms, central venous pressure monitoring, urinary catheter. Best managed in ITU setting.

Type A dissection:

Type A dissection is treated surgically.

Emergency surgery is required because of the risk of cardiac tamponade.

The affected aorta is replaced by a tube graft and the aortic valve may also be replaced.

Type B dissection:

Type B dissection can be treated medically, surgically or by endovascular stenting.

Control the blood pressure of the patient and prevent further dissection with intravenous nitroprusside and/or intravenous labetalol. You may need to use a calcium channel blocker if β-blocker contraindicated.

Surgical repair may be appropriate for patients with intractable or recurrent pain, aortic expansion, end-organ ischemia or progression of dissection, and has similar outcome rates.