Aortic dissection
Summary/Definition
The aortic wall consists of three layers: the inner (tunica intima), middle (tunica media) and outer (tunica externa) layers. The inner layer is the endothelial covering, the middle layer consists of smooth muscle cells, and the outer layer is the elastic membrane. A dissecting aortic aneurysm is a condition in which there is a separation of these layers into inner and outer layers, leading to blood infiltration into the aortic wall. This occurs due to a rupture of the inner layer of the aorta and bleeding into the middle layer, after which the blood spreads along the aortic wall and flows out of the resulting cavity that was previously missing from the aortic structure. An acute aortic dissecting aneurysm is characterized by the presence of bleeding within a newly formed cavity in the aortic membrane. This condition can be divided into 14-day acute aortic dissecting aneurysm, subacute aortic dissecting aneurysm, which lasts from 14 days to 3 months, and chronic aortic dissecting aneurysm, which develops over 3 months. The highest incidence of this disease occurs in the age range of 50 to 60 years, and it occurs twice as often in men as in women. Dissecting aortic aneurysms are classified according to the Stanford and DeBakey systems.
The most common cause is high blood pressure (BP). Approximately 80% of patients with acute aortic dissection have high blood pressure. Aortic dissectings caused by high BP are more often associated with the descending part of the aorta than with the ascending part. In addition, an inherited condition, such as Marfan syndrome, may also be responsible for the development of aortic dissecting aneurysm. Other potential causes include external trauma, coarctation of the aorta, middle-layer necrosis, and other factors. Other factors to consider are cystic aortic radionecrosis, Ehlers-Danlos syndrome, advanced age, presence of bicuspid aortic valve, symptoms of aortic coarctation, external trauma, etc. There is a significantly increased risk of the disease in the third trimester of pregnancy, although the exact causes of this process are still unclear. The disease can also develop as a result of surgical interventions such as catheterization, balloon dilatation, and other surgical procedures.
Symptoms
When an aortic aneurysm is dissected, the patient may experience sudden, intense pain in the back or chest. The pain may spread upward through the body as the aneurysm develops. When a dissecting aortic aneurysm affects the ascending aorta, which is closer to the heart, pain usually occurs in the chest area. In case where the descending aorta, which descends towards the legs, is affected, pain is more likely to occur in the back and abdomen. If the patient has symptoms of loss of consciousness, ischaemic stroke, paralysis of the lower limbs, impaired consciousness and other neurological signs, on initial diagnosis, surgery should be performed in most cases. Sometimes, however, hypovolemic shock and tamponade of the pericardial cavity can occur, which can put pressure on the heart. These situations may be accompanied by heart failure, Quincke’s oedema, intestinal infarction, myocardial infarction and other conditions in which the aortic valve, unable to perform its function, leads to a backflow of blood towards the heart. Rarely, upper respiratory tract closure, bleeding from the oesophagus and stomach, haemoptysis (when blood enters the respiratory tract and oesophagus) and other complications may occur.
Diagnostics
The disease can be detected by electrocardiography (ECG), radiography and echocardiography (echocardiography). In the case of electrocardiography, a myocardial infarction may be diagnosed, the symptoms of which (chest pain) are similar to those of an aortic dissecting aneurysm. However, a simple chest X-ray, which reveals a widening of the mediastinum or the presence of atherosclerotic plaques, with protrusion of the outer wall up to 10 mm, does not always provide an accurate diagnosis. One effective diagnostic method is echocardiography, which allows examination of the heart through the oesophagus, in contrast to the methods used for examination through the chest when an aortic aneurysm is suspected. In addition, CT (computed tomography), MRI (magnetic resonance imaging), aortography and other procedures are used for a more accurate diagnosis.
Treatment and course of the disease
When an untreated aortic dissecting aneurysm is untreated, the mortality rate in the early hours is about 1% with timely emergency treatment. It is necessary to use modern diagnostic methods and appropriate treatment. First of all, blood pressure and heart rate should be immediately reduced, while using hypotensive drugs intravenously. For acute dissecting aneurysms of the ascending aorta, immediate surgical intervention is required. Despite surgical treatment, if there is a suspicion of rupture or threat of rupture when the initial changes have occurred only in the descending aorta, surgery is performed to restore the blood supply to important organs, which is disrupted due to bleeding. The main goal of the surgery is to prevent further up and down aortic stratification and to repair the rupture of the inner sheath, which often requires prosthetic sections of the aorta. An example of such a procedure is aortic replantation surgery. Medication therapy in the acute period is aimed at maintaining the target systolic blood pressure at 100-120 mm Hg and a heart rate of at least 60 beats per minute. For this purpose, beta-blockers, sodium nitroprusside, BCA and other drugs are used. In addition, fentanyl, morphine and other analgesics are used to relieve pain symptoms.
Complications
With the possibility of complications such as aortic valve dysfunction, aneurysm development and aortic rupture, about 20% of patients experience an aneurysm.
