Definition
The term aortic dissection (Syn. Aneurysma dissecans aortae) describes a splitting (dissection) of the wall layers of the aorta. As a rule, the innermost wall layer (tunica intima) is suddenly torn open, resulting in bleeding between the wall layers (the aorta, like any artery, is made up of the three wall layers tunica intima, tunica media and tunica adventitia from the inside to the outside).
Through the tear in the tunica intima, blood from the lumen of the aorta reaches between the wall layers due to the high pressure in the vessel, where it creates a new space (false lumen) between the intima and adventitia. Depending on how high the blood pressure in the aorta is and how resistant the media is, the dissection may extend only a few millimetres or the entire length of the aorta. In the majority of cases, the thoracic aorta (located in the thorax) is affected, most frequently directly above the aortic valve in the ascending portion of the aorta (ascending aorta).
In the clinic, aortic dissection is divided into a type A and B dissection, which will be discussed below. In addition, an acute and a chronic dissection are distinguished. A chronic dissection is present if the symptoms persist for more than two weeks after the acute event, in some cases a chronic dissection lasting several years occurs.
Differentiation
According to Stanford, a simplified and clinically applied classification of aortic dissection exists, which only distinguishes between A and B. In Stanford’s Type A aortic dissection, the tear in the intima is located in the region of the ascending aorta (the ascending part of the aorta that emerges directly from the left ventricle and is followed at the top by the aortic arch). An acute type A dissection is always an immediate indication for emergency surgery to prevent a rupture.
A rupture (tear) of the aorta in the ascending part of the aorta would result in bleeding into the pericardium and immediate heart failure or a tamponade of the pericardium, which would also lead to death quickly. Standard surgical therapy is the replacement of the aorta (usually ascendens) with a gore-tex vascular prosthesis. If the part of the aorta close to the valve is affected, a prosthesis with an integrated prosthesis of the aortic valve is usually used, less frequently the body’s own aortic valve can be reconstructed.
Even a chronic (type A dissection that is symptomatic for more than 2 weeks) usually requires surgical treatment, although this does not require emergency surgery. Type B dissection includes all dissections of the descending aorta (descending part of the aorta behind the aortic arch), or everything below the outlet of the subclavian sinus artery. With type B dissection, the risk of rupture is much lower than with type A dissection.
Since the mortality rate of almost 25% for uncomplicated type B dissections after surgery is significantly higher than for a purely drug treatment (approx. 10%), conservative therapy is usually limited. Exceptions are life-threatening conditions such as an imminent or already occurred rupture. Less dramatic complications can often be treated by catheters with stents inserted through the skin into the vascular system.
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