What is a carotid endarterectomy?|
A carotid endarterectomy is a surgical procedure which re-tunnels the narrowed or blocked lumen (space within the blood vessel) of the carotid artery. The carotid artery is found in the neck and supplies blood to the head.
What causes narrowed or blocked of the carotid artery?
The lumen of the carotid artery can be narrowed or blocked by an atheroma (fatty plaque) and/or a thrombus (aggregation of platelets). An atheroma (+/- thrombus) are commonly found in the region of the carotid bifurcation, where the common carotid artery splits into the internal carotid and external carotid. The internal carotid supplies blood to the brain and the external carotid supplies blood to the rest of the head.
An atheroma is the name given to a fibrofatty plaque of "atherosclerosis", which forms within blood vessels. The exact cause of atherosclerosis is unknown, however from a young age fatty streaks can be found developing in our arteries. Some, but not all of the fatty streaks develop into fibrous plaques, which grow larger over time. The rate at which atherosclerosis develops depends on exposure to a number of environmental factors combined with any genetic predisposition. Risk factors include smoking, high levels of blood cholesterol, diabetes mellitus, saturated animal fats and hypertension.
Genetic factors include variations in the certain proteins found on lipoproteins called HDL (High Density Lipoprotein) and LDL (Low Density Lipoprotein).. High levels of LDL have been associated with a high incidence of atherosclerosis, whereas high HDL levels have been associated with a low incidence of atherosclerosis.
There are a number of complications that may result from atherosclerosis such as blood vessel wall weakening, stenosis (narrowing of lumen), calcification, haemorrhage, and plaque rupture and thrombus formation. A thrombus is an aggregation of platelet cells and clotting proteins, which form as a result of blood vessel damage. So a thrombus is effectively an intravascular clot.
The exposure of an atheroma to blood is prevented by a fibrous cap, however if this fibrous cap is breached, thrombus formation is very rapid and may totally occlude the lumen. The thrombus may disrupt normal blood flow in the carotid or may provide a source for &"thromboembolus’. A thromboembolus is the term given to a fragment of thrombus, which breaks off and lodges in a smaller artery ‘upstream’, occluding it’s blood flow. A thromboembolism from the carotid artery appears to be a major cause of cerebral ischaemia and infarction.
The tissue to which an affected artery supplies may become ischaemic (lack of blood) when the lumen is narrowed beyond the metabolic requirements of that tissue or when the lumen becomes totally occluded resulting in infarction (tissue death). A carotid atheroma or thrombus is a common source for embolism, which blocks cerebral blood vessels. The larger the embolism, the greater the damage to the brain. Stenosis of the cerebral vessels may result in a &"Transient Ischaemic Attack&" and occlusion will result in &"cerebral infarction&" (a stroke),.
What are the symptoms of a narrowed or blocked carotid artery?
Symptoms of carotid stenosis or occlusion include disturbances in vision (&"amaurosis fugax&" is a temporary loss of vision due to retinal ischaemia), dizziness, syncope (fainting), headache, carotid bruit (carotid murmur, i.e. turbulent flow), dementia and stroke deficits due to ischaemia or infarction. Patients most often present after a ‘transient ischaemic attack’ (TIA) or a stroke,.
How is a narrowed or blocked carotid artery diagnosed?
Carotid stenosis is identified by an angiogram. This involves the injection of a radioactive dye into the lower carotid followed by x-ray, MRI (magnetic resonance image) or spiral CT (computerised tomography) to obtain an image of the caro