AORTIC ANEURYSM – Definition, Incidence, Risk Factors, Causes, Pathophysiology, Clinical Manifestations, Diagnostic Evaluation and Management
DEFINITION
- Aneurysm is a localized sac or dilation formed at a weak point in the wall of the aorta.
- An aneurysm is an abnormal bulge in the wall of a blood vessel. A larger bulge, more than 1.5 times the size of normal aorta, is called an aneurysm
INCIDENCE
- 30-60/100
- Increasing incidence over past 3 decades
- Carotid Artery Stenosis – 10%
- Smoker: Nonsmoker – 8:1
- Male: Female – 4:1
- HTN: 40% of pts
Shapes: Aneurysm may be classified by its shape and form:
- True aneurysms: one, two and all three layers of artery may be involved. It is classified into different types:
Fusiform aneurysms: symmetric, spindle-shaped expansion of entire circumference of involved vessel. It appears as symmetrical bulges around the circumference of the aorta. They are the most common shape of aneurysm
Saccular aneurysms: a bulbous protrusion, asymmetrical and appear on one side of the aorta. They are usually caused by trauma or a severe aortic ulcer
Dissecting aneurysms: a bilateral out pouching in which layers of the vessels wall separate creating a cavity. This is usually is a haematoma that split the layer of arterial wall
- False aneurysms: the wall rupture and a blood clot is retained in an out pouching of tissue or there connection between and artery that does not close.
TYPES
The two types of aortic aneurysms are:
- Thoracic aortic aneurysms: develop in the part of the aorta that runs through the chest. This includes the ascending aorta (the short stem of the cane); the aortic arch (the cane handle); and the descending thoracic aorta (the longer stem of the cane).
- Abdominal aortic aneurysms: develop in the part of the aorta that runs through the abdomen. Most abdominal aortic aneurysms develop below the renal arteries (the area where the aorta branches out to the kidneys). Sometimes aortic aneurysms extend beyond the aorta into the iliac arteries (the blood vessels that go to the pelvis and legs).
Causes: the exact cause is unknown. But recent evidence includes:
- Atherosclerosis
- Hypertension
Congenital
- Primary connective tissue disorder (Marfan’s syndrome)
- Turner disorder
Inflammatory (Noninfectious)
- Takayasu’s disease
- Giant cell arteries
- Lupus erythematosus disease
- Behcet’s disease
- Pancreatitis
Mechanical disorder:
- Poststenotic and arteriovenous fistula
- Amputation-related
Traumatic (pseudoaneurysm):
- Penetrating arterial injuries
- Blunt arterial aneurysm
- Pseudoaneurysm
Infectious
- Bacterial
- Fungal
Pregnancy related degenerative:
- Nonspecific
- Inflammatory disease
RISK FACTORS
- CAD
- Hypertension
- Hypercholesterolemia
- Hyperhomocysteinemia
- Elevated C-reactive protein
- Tobacco use
- Peripheral vascular disease
- Marfan’s syndrome
- Ehlers-Danlos type IV
- Biscuspid aorta valve
PATHOPHYSIOLOGY
The physical change in the aortic diameter (can occur) —- secondary to trauma, infection —- an intrinsic defect in the protein construction of the aortic wall (due to) —- progressive destruction of aortic proteins by enzymes —- enlargement of atrial walls
CLINICAL MANIFESTATIONS
- Asymptomatic: 70-75%
- Symptoms
Early satiety, N, V
Abdominal, flank, or back pain
1/3 of patients experience abdominal and flank pain
- Abrupt onset of pain – rupture or expansion of aneurysm
DIAGNOSTIC EVALUATION
Physical Examination
- If >5 cm in diameter, then cannot be detected by routine physical examination
Radiographs
- Calcified wall. Can determine size in 2/3
- Cannot rule out and AAA
Arteriography
- Cannot determine aneurysm size because of mural thrombus
- Indications for obtaining arteriography
Suspicion of visceral ischemia
Occlusive disease of iliac and femoral arteries
Severe HTN, or impair renal function
Horseshoe kidney
Suprarenal of TAAA component
Femoropopliteal aneurysms
Ultrasound
- Establishes diagnosis easily
- Accurately measures infrarenal diameter
- Difficult to visualize thoracic or suprarenal aneurysms
- Difficult to establish relationship to renal arteries
- Technician dependent
- Widely available, quick, no risk, cheap
CT Scan
- Very reliable and reproducible
- Can image entire aorta
- Can visualize relationship to visceral vessels
- Longer to obtain and is more costly than U/S
- Most useful
- Requires contrast agent – renal toxicity
COMPLICATIONS
- Thrombosis
- Distal embolization
- Rupture
