What is Aortic Dissection?
The term aortic dissection - or aortic dissection if you prefer - identifies a serious medical condition in which the inner layer ( intimate habit ) of the largest artery of the organism (the aorta ) is affected by a laceration, through which the blood penetrates and determines the formation of a false lumen .
Commonly, this vascular disease is associated with hypertension, present in more than two thirds of patients. Aortic dissection can be caused by congenital defects and connective tissue disorders, such as Marfan syndrome and Ehlers-Danlos syndrome. Other causes are arteriosclerosis (tissue hardening of the arterial wall) and degenerative and inflammatory processes affecting cardiovascular structures. In rare cases, an aortic dissection occurs accidentally when inserting a catheter into an artery (for example, during an aortography or angiography) or performing surgery.
Aortic dissection occurs with sudden, stabbing pain in the chest and between the shoulder blades. The symptoms may initially simulate those of other diseases, leading to potential delays in diagnosis. However, when an aortic dissection is diagnosed early, the chances of survival are greatly increased. Timely treatment can therefore help to save the patient's life.
Anyone can develop an aortic dissection, but the condition is more frequent in men between 60 and 70 years of age.
Pathogenesis
Like all arteries, the walls of the aorta also consist of three superimposed layers: an intimate habit (the innermost), an intermediate frock and an external tunic or adventitia.
The intima is in direct contact with the blood that flows inside the aorta and is mainly made up of an endothelial lining and the underlying connective layer. The intermediate cassock contains connective and muscular tissue, while the adventitia forms a sheath of connective tissue around the vessel.
In an aortic dissection, the initial event consists of a laceration of the intimate aorta habit. Due to the high pressures to which it is subjected, a separation or delamination progressively develops between the layers of the aortic wall (intimate and medium). This phenomenon allows the penetration of blood under pressure into the intermediate layer and the creation of a false lumen .
Aortic dissection can extend proximally (closer to the heart), distally (away from the heart) or in both directions. If the false lumen extends, it can exert pressure on other branches of the aorta, determining the narrowing of the vessels involved and reducing the flow of blood passing through them.
Predisposing factors
Aortic dissection basically occurs due to the rupture of a weakened area of the aortic wall.
The main risk factors for aortic dissection are:
- Arterial hypertension : makes the vascular tissue particularly susceptible to laceration;
- Arteriosclerosis ;
- Inflammation of the aorta ;
- Aortic aneurysm ;
- Acquired aortic valvulopathies ;
- Congenital cardiovascular anomalies : bicuspid aortic valve (congenital defect of the aortic valve) and aortic coarctation (narrowing of the blood vessel);
- Traumatic injuries : rarely, aortic dissections can be caused by trauma suffered during a car accident, surgery or as a complication of cardiac catheterization.
Some diseases are associated with the weakening of the aorta and, due to their clinical characteristics, expose the subject to a greater risk of undergoing an aortic dissection:
- Marfan syndrome: patients have a congenital predisposition to some alterations of the cardiovascular system. Also the onset of a dissection of the aorta represents a fairly frequent phenomenon, due to the characteristic weakness of the blood vessels resulting from the disease.
- Ehlers-Danlos syndrome: this group of disorders mainly affects connective tissue and is characterized by hyper-elasticity of the skin, laxity of ligaments and fragile blood vessels.
- Turner syndrome: high blood pressure, heart problems and a number of other conditions can result from this disorder.
Other potential risk factors include:
- Cocaine abuse has been associated with aortic dissection, probably due to the temporary increase in blood pressure and catecholamine peaks;
- Rarely, aortic dissections occur in healthy women during pregnancy ;
- Other risk factors are smoking and hypercholesterolemia .
Symptoms
All patients with an aortic dissection experience pain, usually sudden and excruciating, often described as a tear. Commonly, this symptom is felt throughout the chest, but can also be felt in the upper part of the back, between the shoulder blades.
The symptoms of an aortic dissection are:
- Sudden and severe chest pain or upper back pain, often described as a feeling of tearing or shearing, radiating to the neck or along the back.
- Loss of consciousness (fainting);
- Dyspnea (shortness of breath);
- Sudden speech difficulties, loss of vision, weakness or paralysis of one side of the body;
- Sweating;
- Difference in blood pressure in the limbs, on the right and left side of the body.
As the disease progresses, the false lumen may occlude one or more arteries that depart from the aorta, blocking the flow of blood. The direct consequences vary depending on the blood vessels involved and include:
- Angina, due to the involvement of coronary arteries;
- Paraplegia, spinal cord ischemia and paresthesia for spinal artery involvement;
- Ischemia, due to the involvement of the distal aorta;
- Sudden abdominal pain, with possible intestinal infarction, if the arteries of the mesentery are involved;
- Neurological deficit, if the carotid artery is involved.
When blood pressure exceeds a critical limit, rupture of the external aortic wall (adventitious frock) can occur. The blood can escape from the aortic dissection and diffuse into the pleural space, in the mediastinum or in the pericardium (between the two layers of membranes that surround the heart). Pericardial effusion, in particular, can cause cardiac tamponade, a life-threatening pathological condition.
Complications
An aortic dissection can lead to:
- Death, due to severe internal bleeding;
- Organ damage, such as kidney failure;
- Stroke;
- Damage to the aortic valve and aortic insufficiency.
Diagnosis
Formulating the diagnosis promptly can be difficult, as aortic dissection produces a variety of symptoms that sometimes resemble those of other disorders.
The diagnosis can be defined by the following investigations:
- Chest X-ray : this is the first step to identify some signs of aortic dissection. X-rays show a widening of the mediastinum, present in most symptomatic people with ascending aortic dissection. However, the examination has a low specificity, since many other conditions can determine the same outcome.
- Contrast computed tomography (CT) : can quickly and reliably detect aortic dissection, so it is useful in an emergency.
- Electrocardiogram (ECG) : it does not have characteristic features, but can be included in the diagnostic path.
- Magnetic resonance imaging (MRI) : currently magnetic resonance imaging is the reference test for the detection and evaluation of aortic dissection. An MRI exam produces a three-dimensional reconstruction of the aorta, allowing the doctor to determine the position of the intimal tear, the involvement of the vessels and any secondary ruptures.
- Transesophageal echocardiography (TEE) : the ultrasound probe is inserted through the esophagus and positioned near the heart and aorta, allowing a clear "vision" of the heart and its structures. The TEE allows to detect even very small aortic dissections.
Prognosis and Therapy
An aortic dissection constitutes a medical emergency, which requires immediate treatment. Therapy may include surgery or pharmacology, depending on the part of the aorta involved. Without treatment, about 75% of people die within the first 2 weeks, mainly due to complications associated with dissection. With treatment, approximately 70% of patients with dissection in the first part of the aorta (ascending portion) and about 90% of those with the disorder without ascending aorta involvement have a positive prognosis.
People with an aortic dissection are admitted to an intensive care unit, where their vital signs (pulse, blood pressure and respiratory rate) are carefully monitored. Death can occur a few hours after the onset of the disease. Therefore, as soon as possible, intravenous drugs (usually nitroprusside plus a beta-blocker) are given promptly, in order to reduce the heart rate and blood pressure, maintaining a sufficient blood supply to the brain, heart and kidneys. Reduced blood pressure limits the extent of dissection.
Shortly after stabilization by drug therapy, doctors must decide whether to recommend surgery or continue with the administration of drugs. Surgery is often indicated for dissections involving the first centimeters of the aorta (closer to the heart), except for complications that make the risk associated with the operation too high. For dissections located in regions further from the heart muscle, doctors may decide to continue drug therapy. However, surgery is always necessary when the artery dissection causes blood to leak out, blocks the blood supply to the legs or vital organs, causes the onset of severe symptoms, tends to spread or occurs in a person with syndrome of Marfan. During surgery, surgeons remove the affected aorta section, close the false lumen and reconstruct the blood vessel with a synthetic prosthesis. Removal and repair take about 3-6 hours and hospital stay is approximately 7-10 days. In some cases, an endovascular stent may be inserted. This procedure takes 2 to 4 hours and the hospital stay takes about 1-3 days.
Type A aortic dissection (Stanford classification)
Type A represents the most common and dangerous form of aortic dissection.
Type B aortic dissection
Type B aortic dissection involves a tear in the descending aorta, which can also extend into the abdomen. In this case, patients can be treated with drugs or surgically. For patients presenting asymptomatic distal aorta dissection, drug therapy is a sufficient option. Surgical options for type B aortic dissection are similar to the procedures used to correct a type A dissection. Stents may sometimes be introduced to repair the blood vessel.
drugs
Aortic dissections can be treated with drugs - such as beta-blockers (eg: labetalol and esmolol) and sodium nitroprussiate - which relieve blood pressure on the aortic wall, stopping the progression of the disorder. By reducing blood pressure, aortic dissection is less likely to get worse. These drugs can also be used to prepare a patient for surgery.
After treatment, many patients, including those treated surgically, are prescribed drug therapy to maintain low blood pressure. Long-term drug therapy usually consists of beta - blockers or a calcium channel blocker, plus another anti-hypertensive drug, such as ACE inhibitors (Angiotensin-converting enzyme inhibitors). If the patient is atherosclerotic, changes are made in the diet and cholesterol-lowering drugs are indicated.
Periodic checks allow monitoring of aortic dissection and prompt action to deal with any late complications, such as the onset of another intimal laceration or the development of weakened aortic aneurysms (all conditions that may require surgical repair).
