Aneurysmal Disease**

Question 1

Definition of aneurysm

Answer 1

An aneurysm is a localised abnormal dilation of a blood vessel or the wall of the heart. These can be congenital or acquired.

Question 2

Classification of aneurysms

Answer 2

1. Saccular: smaller, spherical aneurysms that can particularly predispose to thrombus formation within them; or
2. Fusiform: circumferential dilation of a long vascular segment.

Question 3

True aneursysms

Answer 3

A true aneursysm is bounded by all of the arterial wall components or the dilated wall if the heart e.g. atherosclerotic, aymphilitic, congenital vascular (berry) aneurysms (of the circle of Willis - vessels at the base of the brain) and left ventricular aneurysm.

Question 4

Aetiology of true aneurysms

Answer 4

Weakness of the vascular wall, increased collagen vreakdiwn compared to synthesis by local inflammation, loss of vessel smooth muscle contribute to the development of aneurysms.

Ischaemia secondary to atherosclerosis and systemic HTN narrowing the vaso vasorum is another important cause.

Genetic predisposition towards aneurysmal formation also relates to collagen disorders (e.g. Marfans syndrome) and matrix metalloproteinase (MMP) abnormalities. This can result in histologically what is termed ‘cystic medial degeneration’.

Question 5

Aetiology of berry aneurysms

Answer 5

Atherosclerosis is *not *a risk factor for berry aneurysms. It is caused by a congenital weakness of the vessels of the circle of Willis at teh base of the brain.

Question 6

False aneurysms

Answer 6

A false aneurysm is a breach in the vascular wall leading to an extravascular hematoma that freely communicates with the intravascular space (pulsating haematoma). e.g. a post-myocardial infarction rupture that has been contained by a pericardial adhesion, a leak at the junction (anastamosis) of a vascular graft with a natural artery, or the site of arterial puncture (femoral artery) following angioplasty.

Question 7

Clinical features of aneurysms

Answer 7

May be asymptomatic until a complication arises. May be identified on physical examination. May be identified incidentally in medical imaging.

Question 8

Abdominal aortic aneurysm (AAA)

Answer 8

Atherosclerosis, HTN and unknown factors lead to medial degeneration that occurs most frequently in the abdominal aorta - usually below the renal arteries and above the bifurcation into the common iliacs.

M>F, >50 years old, smokers, family history, rupture is related to size of the aneurysm.

Question 9

AAA complications

Answer 9

1. Rupture into the peritoneal cavity of retroperitoneal tissues with massive haemorrhage. Risk of rupture:
   
   • 1% per year 4.0-4.9cm
   • 11% per year 5.0-5.9cm
   • 25% per year >6cm
2. Obstructtion of a branch vessel, particularly of the iliac, renal, mesenteric or vertebral branches.
3. Embolism from atheroma or mural thrombus (watch out for ischaemic lower limb/toes).
4. Impingement on an adjacent structure
5. Arterial dissection

Question 10

Thoracic Aortic Aneurysm

Answer 10

More commonly associated with HTN, Marfans syndrome.

Question 11

Arterial dissection

Answer 11

Arises when bloo enters the wall of the artery, as a haemoatoma dissecting between its layers following an intimal tear.

Dissection may, but not always, arise in aneurysmal arteries.

Most commonly seen in the thoracic aorta - known as an aortic dissection.

Question 12

Arterial dissection clinical presentation

Answer 12

90% in older men (40-60 yo) with history of HTN or younger men with history of CT weakness (e.g. Marfans Syndrome) or iatrogenic complicating arterial cannulation.

Aortic dissection clasifcally presents as excruciating pain, beginning in the anterior chest, radiating to the back between the scapulae and moving downward with progression.

The dissection may rupture leading to blood in the pericardial, pleural or peritoneal cavities.

Treatment includes intensive antihypertensives and repair.