The aorta is the body's main artery: the thick-walled highway that carries oxygen-rich blood straight from the heart to every organ. It is built of three layers of tissue, like a reinforced tube. In aortic dissection, a tear develops in the innermost layer, and blood forces its way between the layers, splitting them apart. In the worst cases, the outer wall can rupture, and blood floods into the chest or abdomen.
The single biggest risk factor is high blood pressure. Years of uncontrolled hypertension slowly weaken the aortic wall, making the inner lining more vulnerable to a sudden tear. Other contributors include connective-tissue disorders, a bicuspid aortic valve (a heart valve with two flaps instead of three), inherited aortopathies, and, in some cases, trauma or an underlying aneurysm.
The classic symptom is the abrupt onset of severe tearing or ripping pain in the chest or back, but dissection can mimic a heart attack, a stroke, or even kidney trouble — which is why it is dangerous. Misdiagnosis is common, and the condition has a high mortality rate in the hours after the tear occurs.
Diagnosis relies on imaging: a CT angiogram, a transoesophageal echocardiogram or magnetic resonance imaging can visualise the tear and the path of the false channel. Treatment depends on which part of the aorta is involved. Tears near the heart (type A) generally require emergency open-heart surgery to replace the damaged section; tears further down (type B) are often managed medically with drugs to lower blood pressure and reduce the force of each heartbeat. Patients who survive require long-term monitoring, because the aorta above or below a repair can weaken again.