Aortic Dissection: Types, Risk Factors, Clinical Features, Diagnosis, and Management

Introduction:

Aorta is the largest blood vessel in the body that carries oxygen in the blood from the heart to different parts of the body. The aortic wall is divided into three layers- an inner layer (intima), a middle layer (media), and an outer layer (adventitia). Aortic dissection is a life-threatening condition leading to death if not treated immediately.

What Is Aortic Dissection?

Dissection of the aorta is a tear in the inner layer of the aorta that causes the leakage of blood into an undesired area making the inner and middle layers separate or dissect and resulting in bursting or pooling of blood from the outer wall. This in turn causes decreased systemic blood pressure and the pooled blood surrounds the outer layer of the heart (pericardium) causing hemopericardium. Aortic dissection is also associated with cardiac tamponade (inability of the heart to contract and relax due to less space caused by the pericardial pooling of the blood), leading to sudden death.

What Are the Types of Aortic Dissection?

An aortic dissection occurs due to damage to the wall of the aorta. Aortic dissection is of two types, depending on the part of the aorta affected.

• Type A: It is quite a common and potentially life-threatening type as it is associated with a tear in the region where the aorta leaves the heart. The tear can be present in the upper aorta (ascending aorta) and can even extend into the abdomen.

• Type B: The tear occurs in the lower aorta only (descending aorta), which may also extend into the abdomen.

What Causes Aortic Dissection?

• Aortic dissection occurs due to a slow damaging process of cells in the aortic wall. The damage goes undetected for many years until it becomes full-blown and forms a tear in the wall of the aorta.

• The aortic wall exposure to constant pulsatile pressure and shear stress causes a tear in the inner lining of the wall, especially in susceptible patients.

• The tear causes the blood to flow in an undesired region to form a false lumen.

• Most of the tear occurs in the ascending aorta, as it is susceptible to the greatest shear force.

What Are the Risk Factors of Aortic Dissection?

The risk factors of aortic dissection include:

1. Anatomic Factors:

• Uncontrolled high blood pressure.

• Hardening of the arteries (atherosclerosis).

• Weakened and bulging artery (aortic aneurysm).

• An aortic valve defect (bicuspid aortic valve).

• Narrowing of the aorta at birth (aortic coarctation).

2. Genetic Factors:

• Turner Syndrome: Poses a high risk of aortic dissection, high blood pressure, heart problems, and other health conditions that may result from this disorder.

• Marfan Syndrome: This is a condition in which connective tissue becomes weak. People with this disorder do have a family history of aneurysms of the aorta and other blood vessels or a family history of aortic dissections.

• Other Connective Tissue Disorders: This includes Ehlers-Danlos syndrome, a group of connective tissue disorders that involve loose joints and fragile blood vessels, and Loeys-Dietz syndrome, which causes twisted arteries, especially in the neck, making the walls weak.

• Giant Cell Arteritis: Also increases the risk of aortic dissection.

3. Other Factors:

• Sex: Men are more likely to have aortic dissection than women.

• Age: Aortic dissection is more common in people aged 60 years and older.

• Cocaine Use: This drug may raise blood pressure, which is a risk factor as high pressure causes strain on the walls of the arteries.

• Pregnancy: Aortic dissections occur in otherwise healthy women during pregnancy in some cases.

• High-Intensity Weightlifting: Strenuous resistance training raises the risk of aortic dissection by increasing blood pressure during the activity.

What Are the Clinical Features of Aortic Dissection?

The most common feature of aortic dissection is its abrupt onset, which can occur at any time when the patient is at rest or sleeping. Common signs and symptoms include,

• Acute severe tearing, stabbing, or ripping type of sharp pain in the chest or upper back.

• Shortness of breath.

• Fainting or dizziness.

• Low blood pressure and the patient is at high risk when there is a 20 mmHg pressure difference between arms.

• Diastolic heart murmur, muffled heart sounds.

• Rapid, weak pulse.

• Heavy sweating.

• Confusion.

• Loss of vision.

• Stroke symptoms include weakness or paralysis on one side of the body.

• Difficulty in talking.

How Is Aortic Dissection Diagnosed?

• Chest X-ray: Chest X-ray is useful as it reveals the chest, including the heart, lungs, blood vessels (aorta), and bones. This test is not specific but aids in timely diagnosis.

• Computed Tomography (CT) Scan: Provides the best view of the aorta in cases of aneurysm or dissection. For aortic imaging, intravenous (IV) contrast dyes are used.

• Transthoracic Echocardiogram: Uses ultrasound to provide moving pictures of the heart valves, chambers, and aorta.

• Transesophageal Echocardiogram (TEE): Provides detailed pictures of the heart valves and chambers than a transthoracic echocardiogram and better views of the thoracic aorta.

• Magnetic Resonance Imaging (MRI): It provides moving pictures of the heart valves and chambers and blood flow through the aorta. But requires more time than a typical CT scan and so is less commonly used in emergencies.

What Are the Complications of Aortic Dissection?

The major complications of aortic dissection include:

• Death due to severe internal bleeding.

• Organ damage, such as kidney failure or life-threatening intestinal damage.

• Stroke.

• Aortic valve damage (aortic regurgitation) or rupture into the lining around the heart (cardiac tamponade).

How Is Aortic Dissection Managed?

Management of aortic dissection is based on the site where the tear and dissection have occurred. Immediate surgery has to be carried out in type A aortic cases (where it involves the first part of the aorta close to the heart). Type B aortic dissection requires emergency surgery if the dissection cuts off the blood flow to the vital organs, including kidneys, intestines, legs, or spinal cord. Emergency surgery is also carried out when CT scan findings show certain high-risk findings. Mild cases can be treated with medication initially, and surgery can be delayed unless there is a risk of potential complications.

Treatment options include:

1. Surgery/Graft Replacement: A part of the damaged tissue of the aorta is removed and replaced with a synthetic fabric tube (graft).

2. Endovascular Stent-Graft Repair:

• A stent graft (synthetic fabric tube supported by metal wire stents like a scaffold) is used to repair the damaged part inside the aorta.

• A small incision is made in the groin region, and a catheter, with the fabric-lined stent attached, is delivered and placed into the aorta under X-ray guidance. At the repair site, the stent graft is released like a spring or umbrella, which opens up to reline and reinforce the weak area of the aorta.

3. Hybrid Approach:

• A combination of conventional open surgery and endovascular stent-graft technique is employed to repair the aorta.

• This technique is indicated when the aortic arch requires repair as it gives rise to branches supplying the brain and the arms. It is an emergency procedure and is carried out in type A cases. One of the most common hybrid procedures is called the “elephant trunk” or “frozen elephant trunk” procedure.

4.Medications:

• Beta-blockers are prescribed to decrease the heart rate and blood pressure. Sometimes, medication alone can treat type B aortic dissection cases, and surgery can be delayed until any potential complications arise.

How Can One Prevent Aortic Dissection?

Congenital defects or being born with genetic or connective tissue disorders increase the risk of developing aortic dissection and cannot be prevented. However, like any other medical disease and condition, one can modify certain lifestyle choices, which can reduce the risk of aggravating the condition, and the modifications include:

• Normalizing high blood pressure to 120/80 mm/Hg with the help of medications, dietary changes, and other measures recommended by the doctor.

• Quitting smoking and using tobacco products and maintaining a healthy weight.

• Wearing the seat belt while driving prevents injury to the chest in case of an accident.

• Visiting the doctor regularly and being under their constant supervision in high-risk cases.

• Also, it is crucial for a first-degree relative of a person who has had an aortic dissection to be screened for the risk of aortic disease and should be closely monitored to prevent an uneventful aortic event.

Conclusion

Aortic dissection is a medical emergency with a very high mortality rate if it is left undiagnosed. The majority of patients present in the emergency department, and several studies have proven that patient outcomes are improved when managed with an interprofessional team of healthcare professionals. One can reduce the risk of aortic dissection by preventing chest injury and making better lifestyle choices to keep the heart healthy.