Aneurysmal Disease

Aneurysm
Definition: Localised abnormal dilatation of a blood vessel or the heart.

True Aneurysm
Definition: An aneurysm which involves all 3 layers of blood vessel wall or heart

Abdominal Aortic Aneurysm (AAA)
Definition: Aneurysm occurring in abdominal portion of aorta (usually infra-renal).
Demographics: More common with increasing age, present in 5% of population above 60 years of age. 5 times more frequent in males. 1 in 4 male children of affected individual will develop it.
Causes: Secondary to atherosclerosis, infection, trauma, genetic diseases (eg. Marfan’s / Ehlers-Danlos syndromes).
Symptoms: Most asymptomatic. Obstruction of proximal organs (eg. ureter, duodenum, vena cava). Rupture: Severe pain (epigastric with radiation to back), hypotension, tachycardia, anaemia, sudden death (90% mortality).
Signs: Pulsatile, expansile abdominal mass. “Trash feet” (ie. forefoot / toe ischaemia) due to emboli.
Investigations: Ultrasound, CT scan.
Management: Lifestyle changes (smoking, diet, hypertension control etc.), medical (lipid-lowering, anti-hypertensive drugs), surgery (necessary in emergency case of rupture, otherwise elective).
Prognosis: Return to normal activities within few months of repair.

Thoraco-Abdominal Aneurysm (TAA)
Definition: Aneurysm occurring in ascending, arch or descending thoracic aorta.
Demographics: Most common in individuals with Marfan’s syndrome and hypertension.
Causes: Secondary to atherosclerosis.
Symptoms: Most asymptomatic. Stridor (high-pitched, turbulent air flow in upper airway) due to compression, haemoptysis (coughing blood) due to aortobronchial fistula, hoarseness due to compression of recurrent laryngeal nerve. Rapid expansion: Chest pain radiating to back. Rupture: Hypotension, tachycardia, death.
Investigations: CT scan, aortography, transoesophageal echocardiography.
Management: Operative repair, stenting.

Syphilitic Aneurysm
Syphilis causes inflammation and narrowing of vasa vasorum in ascending and arch of aorta. This leads to ischaemic damage to media, causing fibrosis and loss of elasticity. Aneurysm results.

Mycotic Aneurysm
Infection of media via vasa vasorum (can occur in root of aorta) weakens arterial wall causing aneurysm. Often underlying bacterial endocarditis.

False Aneurysm (Pseudoaneurysm)
Definition: An aneurysm which breaches the vascular wall but is contained by extra-vascular tissues, forming a haematoma.

Ventricular Rupture
Following myocardial infarction, fibrosis of ventricular walls may cause a rupture, resulting in a haematoma that is contained within the pericardium.

Traumatic Rupture
Often the result of traumatic rupture or perforating injury (eg. during arteriography or angioplasty).

Dissection
Definition: Blood enters the wall of an artery as a haematoma, dissecting its layers.

Aortic Dissection
Definition: Blood enters lamina planes of the media to form blood filled channels within the aortic wall. Type A: aortic arch and valve proximal to origin of left subclavian artery. Type B: descending thoracic aorta distal to origin of left subclavian artery.
Demographics: Either hypertensive men aged 40-60 (90% of cases) or younger individuals with systemic or localised connective tissue abnormalities (eg. Marfan’s syndrome).
Causes: Hypertension, connective tissue disorder (eg. Marfan’s syndrome, Ehlers-Danlos syndrome, vitamin C deficiency, etc.) iatrogenic (eg. diagnostic catheterisation, pulmonary bypass), during or after pregnancy.
Symptoms: Severe central chest pain radiating to back and down arms.
Signs: Shock, neurological symptoms secondary to spinal cord ischaemia, renal failure, acute lower limb ischaemia, visceral ischaemia, absent peripheral pulses.
Investigations: Chest X-ray, CT scan, transoesophageal echocardiography.
Management: Medical (urgent anti-hypertensive drugs). Type A: arch replacement surgery. Type B: medical treatment.

References:
1. Kumar and Clark: Clinical Medicine, 6th ed.
2. Robbins Basic Pathology, 8th ed.
3. Underwood: General and Systemic Pathology, 4th ed.