A dissecting aneurysm, more accurately called an aortic dissection, is a serious emergency in which a tear forms in the inner layer (intima) of the aortic wall, allowing blood to surge through the tear and split the layers of the aortic wall apart, creating a false channel (false lumen) running parallel to the true lumen. The pressure of blood flowing through this false channel can propagate the tear along the length of the aorta, sometimes extending into branches supplying the coronary arteries, brain, kidneys, or spinal cord.
Aortic dissection is classified by location. Type A dissection involves the ascending aorta and is a surgical emergency with very high short-term mortality without intervention, as it can cause cardiac tamponade, aortic valve regurgitation, or blockage of the coronary artery origins (causing heart attack). Type B dissection involves only the descending aorta and is usually managed medically unless complicated by end-organ ischaemia or expansion.
Symptoms typically include sudden, severe, tearing or ripping chest pain radiating to the back, often described as the worst pain the person has ever experienced. Other features depend on which arteries are affected: stroke if carotid arteries are involved, leg weakness if spinal arteries are affected. Diagnosis is made by CT angiography, which clearly shows the true and false lumens.
Predisposing conditions include uncontrolled hypertension (the most common cause), inherited connective tissue disorders such as Marfan syndrome and Ehlers-Danlos syndrome, bicuspid aortic valve, and previous aortic surgery. Cardiac arrest caused by aortic dissection has a poor prognosis, but survivors require urgent surgical or endovascular repair.
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