Aortic Dissection is an acute or chronic disorder in which a tear or disruption in the aortic wall permits blood to enter the wall and create a false channel between its layers. The resulting separation can extend along the aorta and may obstruct branches supplying the brain, spinal cord, kidneys, intestines or limbs. It can also cause aortic rupture, acute aortic regurgitation, cardiac tamponade or other life-threatening complications. Dissection is distinct from Aortic Aneurysm, although aneurysmal dilation and dissection can be related. The Stanford classification divides dissections into type A, involving the ascending aorta, and type B, which does not involve the ascending aorta.
Chronic hypertension is an important risk factor for Aortic Dissection because sustained pressure places mechanical stress on the aortic wall. Other risk factors include increasing age, known aortic aneurysm, bicuspid aortic valve, previous aortic surgery and inherited connective-tissue disorders such as Marfan syndrome, Loeys-Dietz syndrome and vascular Ehlers-Danlos syndrome. Certain inflammatory aortic conditions can also weaken the vessel wall. Pregnancy and the postpartum period can be associated with increased risk in susceptible individuals, particularly when an underlying aortopathy exists. Trauma and iatrogenic injury can cause related forms of aortic wall disruption.
The classic presentation is sudden severe chest or back pain, often described as abrupt in onset, although the location and character can vary. Pain may migrate as the dissection extends, but this feature is not present in every case. Neurological symptoms can occur if cerebral or spinal arteries are affected, while limb pain, weakness or absent pulses can occur with branch-vessel obstruction. Mesenteric involvement can cause abdominal pain and intestinal ischaemia, while renal involvement can impair kidney perfusion. Some dissections present with syncope, heart failure, shock or other complications rather than classic pain.
Type A Aortic Dissection involves the ascending aorta and is particularly dangerous because it can rapidly cause pericardial tamponade, severe aortic regurgitation, coronary artery involvement or extension into the aortic arch and cerebral vessels. It generally requires urgent surgical assessment and repair. Type B dissection begins distal to the branches of the aortic arch and does not involve the ascending aorta. Uncomplicated type B disease is often initially managed with intensive medical control of blood pressure and heart rate, while complicated cases involving rupture, malperfusion, persistent pain or uncontrolled hypertension may require endovascular or surgical intervention.
Diagnosis must be rapid because clinical deterioration can occur suddenly and the condition can resemble other causes of acute chest or back pain. Computed tomography angiography is widely used in stable patients because it can rapidly demonstrate the intimal flap, true and false lumens and involvement of branch vessels. Transoesophageal echocardiography can be useful in unstable patients or when bedside assessment is necessary, while magnetic resonance imaging can provide excellent anatomical detail but is generally less practical for many emergency presentations. A normal chest X-ray does not reliably exclude dissection.
Immediate medical management commonly focuses on reducing aortic wall stress by controlling heart rate and blood pressure, usually with intravenous medications in an acute setting. Beta-blockade is commonly used unless contraindicated, with additional blood-pressure control as required. Pain management is also important because severe pain increases sympathetic activation and can worsen haemodynamic stress. The precise blood-pressure target and medication sequence depend on the clinical situation, and treatment must avoid compromising perfusion to organs affected by the dissection. Type A disease generally requires urgent surgical intervention, while selected type B disease can be treated endovascularly.
Complications of Aortic Dissection depend on the extent and location of the tear. Rupture into the pericardium can cause tamponade, while involvement of the aortic valve can cause acute severe regurgitation and heart failure. Coronary involvement can produce myocardial infarction, cerebral involvement can cause stroke, and obstruction of renal or mesenteric arteries can cause organ ischaemia. Limb malperfusion can threaten tissue viability. Even after initial survival, patients require long-term surveillance because the residual dissected aorta can enlarge, develop aneurysmal degeneration or become the site of recurrent complications.
A common misconception is that aortic dissection always produces unbearable chest pain or that a normal initial test excludes it. Presentations can be atypical, pain can be absent or less characteristic, and some investigations have limited sensitivity. Another misconception is that dissection is simply a ruptured aneurysm; the defining process is separation of the layers of the aortic wall by blood entering through a tear. Because treatment differs according to anatomical classification and complications, suspected Aortic Dissection is an emergency requiring rapid specialist assessment, appropriate imaging and immediate control of haemodynamic stress.
