Aortic dissection

Definition

Aortic Dissection occurs when pathological thinning or dilation of the aorta (aneurysm), either within the thoracic cage or abdominal cavity, ruptures under stress. There are a range of symptoms congruent with the specific region of the rupture and a relative likelihood of dissection occurring.

Pathogenesis

In an aortic dissection the primary cause is an aneurysm. The cause of an aneurysm can vary and mostly occur in normal tissue, but some do occur with a congruent proliferative atherosclerotic plaque. Weakening of the aortic intima creates a blood filled space in the media which dilates and can be stable for several years. Under duress (i.e elevated blood pressure) or through further weakening of the media (cysic medial necrosis) the dilation may rupture and the blood eject through the adventia into the pericardial space.

Clinicopathological Features

The symptoms of an aortic dissection are varied. Firstly the decrease in blood pressure can be appreciated with the symptoms of shock and a loss of peripheral pulses. Chest pain radiating to the back is common. The patient will rapidly deteriorate and syncope will occur due to reduced brain oxygenation. Rapid multisystem failure will follow. Haemopericardium (due to filling) will compress the organs of the thoracic cage and present with rapidly progressing dyspnoea. If not corrected death will follow rapidly.

Risk Factors

Systemic Hypertension Any condition increasing blood pressure. Marfans Syndrome

Prognosis

Without treatment the 48hr mortality is 50% and 90% in one week.

Treatment

The initial aim is to contain the bleeding and reduce blood pressure. .This can be achieved through the administration of any drug functioning to suppress cardiac function (beta blockers etc), lower systemic pressure (aspirin, heparin, warfarin) or in a longer term counteract the effects of reduced renal flow (ace inhibitors.)Drainage of haemopericardium is also imporant to ensure adequate ventilation Surgery is then the gold standard with a higher success rate if the tear is in the proximal aorta.