Aortic Aneurysm, Dissection, and Rupture

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Diagnosis | Management

Definition

Aortic aneurysm is an abnormal dilation of the aorta, the largest artery in the body, due to weakness in the vessel wall. An aneurysm can occur anywhere along the aorta, but it is most commonly found in the abdominal aorta (abdominal aortic aneurysm or AAA) or the thoracic aorta (thoracic aortic aneurysm or TAA).

Aortic dissection occurs when there is a tear in the innermost layer of the aorta's wall, allowing blood to flow between the layers of the vessel wall, causing them to separate. This condition is life-threatening and requires immediate medical attention.

Aortic rupture is the most catastrophic outcome of an aortic aneurysm or dissection, where the aorta bursts, leading to massive internal bleeding, shock, and often death.

Aetiology

The causes of aortic aneurysm, dissection, and rupture are often related but can vary:

• Atherosclerosis: The most common cause, where plaque builds up in the arteries, weakening the vessel walls.
• Genetic conditions: Marfan syndrome, Ehlers-Danlos syndrome, and other connective tissue disorders can predispose individuals to aneurysms and dissections.
• Hypertension: Chronic high blood pressure puts extra stress on the aorta, leading to weakening and potential tearing.
• Infection: Conditions like syphilis or tuberculosis can lead to inflammatory weakening of the aorta.
• Trauma: Severe chest or abdominal trauma, such as from a car accident, can cause aortic dissection or rupture.
• Aortic wall inflammation: Vasculitis or other inflammatory conditions can lead to aneurysm formation.
• Smoking: Smoking is a major risk factor that accelerates atherosclerosis and weakens the aortic wall.

Pathophysiology

The pathophysiology of aortic aneurysm, dissection, and rupture involves a progression from weakening of the aortic wall to catastrophic failure:

Aortic aneurysm: The aortic wall weakens due to factors like atherosclerosis, hypertension, and genetic conditions. Over time, the vessel wall stretches and forms an aneurysm. The aneurysm expands as the wall continues to weaken, increasing the risk of rupture.

Aortic dissection: In dissection, a tear in the intima (inner layer) of the aorta allows blood to enter the medial layer, creating a false lumen. This can extend along the aorta, disrupting blood flow to vital organs and weakening the aortic wall further, potentially leading to rupture.

Aortic rupture: If an aneurysm or dissection progresses unchecked, the aortic wall can no longer contain the blood pressure, leading to rupture. This results in massive haemorrhage, hypovolaemic shock, and death if not treated immediately.

Risk Factors

Key risk factors for aortic aneurysm, dissection, and rupture include:

• Age: The risk increases with age, particularly in individuals over 60.
• Gender: Males are more commonly affected than females.
• Hypertension: Chronic high blood pressure is a significant risk factor.
• Smoking: Smoking greatly increases the risk of aortic aneurysm and its complications.
• Family history: A family history of aortic aneurysm or dissection increases risk.
• Connective tissue disorders: Conditions such as Marfan syndrome and Ehlers-Danlos syndrome are major risk factors.
• Atherosclerosis: The presence of plaque in the arteries contributes to aneurysm formation.
• High cholesterol: Elevated cholesterol levels contribute to atherosclerosis and aneurysm risk.
• Inflammatory diseases: Conditions like vasculitis can weaken the aortic wall.

Signs and Symptoms

The signs and symptoms vary depending on whether the patient has an aneurysm, dissection, or rupture:

• Aortic aneurysm: Often asymptomatic until it becomes large or ruptures. Symptoms may include back pain, abdominal pain, or a pulsatile abdominal mass.
• Aortic dissection: Sudden, severe chest or back pain, often described as "tearing" or "ripping." The pain may radiate to the neck, jaw, or arms. Other symptoms may include shortness of breath, fainting, and symptoms of stroke if the dissection affects blood flow to the brain.
• Aortic rupture: Sudden onset of severe pain, hypotension, loss of consciousness, and shock. Rupture is a medical emergency with a very high mortality rate if not treated immediately.

Investigations

Key investigations for diagnosing aortic aneurysm, dissection, and rupture include:

• Ultrasound: The first-line investigation for screening and diagnosing abdominal aortic aneurysms.
• CT scan: A CT angiogram is the gold standard for diagnosing aortic dissection and evaluating aneurysm size and risk of rupture.
• MRI: Useful in diagnosing aortic dissection, especially in patients who cannot undergo CT scanning.
• Chest X-ray: May show a widened mediastinum in cases of aortic dissection, although not diagnostic.
• Echocardiography: Particularly transoesophageal echocardiography (TOE) can be used to diagnose aortic dissection.
• Blood tests: To assess overall health and organ function, particularly in the context of rupture or dissection.

Diagnosis

Diagnosis is based on clinical presentation, imaging studies, and the patient's medical history. Immediate imaging with a CT scan or ultrasound is crucial for confirming the diagnosis and determining the appropriate treatment plan.

Management

Management strategies vary depending on whether the condition is an aneurysm, dissection, or rupture:

• Aortic aneurysm: Small, asymptomatic aneurysms may be monitored with regular imaging. Larger aneurysms or those causing symptoms often require surgical intervention, such as endovascular aneurysm repair (EVAR) or open surgical repair.
• Aortic dissection: Dissections require immediate medical attention. Type A dissections (involving the ascending aorta) generally require emergency surgery, while Type B dissections (involving the descending aorta) may be managed medically with blood pressure control, though some cases also require surgery.
• Aortic rupture: This is a surgical emergency. Immediate resuscitation and surgical repair are necessary to prevent death. The patient may require massive transfusion, blood pressure support, and rapid transport to a specialist surgical centre.
• Blood pressure management: Essential in preventing the progression of aneurysms and dissections, typically involving beta-blockers, ACE inhibitors, or other antihypertensives.
• Lifestyle modifications: Smoking cessation, regular exercise, and a healthy diet are crucial in reducing the risk of aortic complications.

References

1. National Institute for Health and Care Excellence (NICE) (2024) Management of Aortic Aneurysm. Available at: https://www.nice.org.uk/guidance/ng156 (Accessed: 26 August 2024).
2. British Heart Foundation (2024) Aortic Aneurysm, Dissection and Rupture. Available at: https://www.bhf.org.uk (Accessed: 26 August 2024).

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