The aorta is the main blood vessel that carries high pressure blood out of the heart. It gives off branches to the head and neck and arms then arches over the back of the chest alongside the backbone down into the abdomen, giving off further branches to the internal organs. The aorta is a tough tube made of smooth muscle cells and elastic proteins. It is lined by a special layer called the tunica intima. Aortic dissections are a result of the internal layer of intima tearing and separating from the outer layers. This forms a flap of tissue inside the aorta. The tear usually starts high in the chest just where the aorta arches over to travel down the body. The acute tear may be extremely painful, felt in the chest and back as a searing sensation, sometimes mistaken for a heart attack. Not all dissections are painful, sometimes a dissection is detected in a patient who has no recollection of any painful attacks.
Aortic dissections cause two main problems. First, the torn lining may form a flap of tissue which blocks the flow of blood into the branches of the aorta. The consequences of this depend on which branch is affected. For example, if an artery to the head and neck is blocked, major stroke may result. If the artery involved is supplying a kidney, renal failure may be precipitated. The second problem is a longer term issue. The segment of aorta which has lost its normal lining is weakened, and in time may balloon out and form an aneurysm. An aneurysm is an abnormal bulging of a blood vessel that is prone to bursting. For these reasons, it is always worth considering treating aortic dissections.
All patients with aortic dissections need very careful control of blood pressure as this reduces the risk of long term complications of the condition. More than one type of blood pressure medication may be needed, and beta blocker tablets are nearly always included in the treatment. Some patients with aortic dissection benefit from endovascular treatment with aortic stent-grafting. This procedure is a key-hole operation to place a tough new lining inside the torn aorta to prevent progression of the condition and protect against aneurysm formation. This is also known as thoracic endografting. The graft is placed via the femoral artery in the groin or via the iliac artery in the lower abdomen and manipulated to the correct position under X-ray control. This is usually done under epidural anaesthetic without the need for general anaesthetic, so even quite unfit patients can benefit.