Atherosclerosis is a disorder of the blood vessels, especially the arteries, where there is deposition of fatty plaques (atheroma) in the inner layer (tunica intima) of the artery wall. It is a progressive disorder meaning it gets worse over time although this is a slow process. The fatty plaque is made of up of different lipids like cholesterol, some blood cells and calcium. As it grows it narrows the interior of the artery and gradually restricts blood flow.
Atherosclerosis virtually affects all the blood vessels of the body but important large arteries are most commonly affected. This includes the aorta, renal (kidney) arteries, mesenteric (intestinal) arteries and the carotid (neck) arteries. The medium-sized to small arteries frequently involved are the coronary arteries which supply blood to heart, cerebral (brain) arteries and the arteries of the lower limbs.
Atherosclerosis is a disease that starts in early in life, sometimes as early as in childhood or adolescence. Most of the time however, it starts in early adulthood. The symptoms often do not appear before the fourth decade of life until the fatty plaque (atheroma) becomes large enough to significantly affect blood supply to a specific area and produce symptoms. The important effects seen due to atherosclerosis in the more commonly affected organs causes different symptoms.
Coronary heart disease or ischemic heart disease and its outcomes like angina pectoris, myocardial infarction and sudden death. Symptoms include chest pain during stress, dizziness, nausea and arm or jaw pain.
Decreased blood supply to the brain may develop gradually over a period of time causing episodes known as transient ischemic attacks (TIAs) and eventually leading to a cerebral infarction (brain stroke). Symptoms vary between dizziness, fainting, loss of vision, muscle weakness or paralysis, loss of memory, dementia and numbness of body parts.
This is known as peripheral vascular disease. Initially there is pain in the legs upon walking then even at rest (claudication) over time. The legs may appear pale in color and dark leathery patches may form on the skin or even ulcers. If the blood supply is severely affected, then portion of the tissue in the leg may die thereby presenting as gangrene.
The exact cause of atherosclerosis is not known but studies have found that presence of certain risk factors increases the risk of developing atherosclerosis. This includes :
- High blood pressure
- High cholesterol levels
- Diabetes mellitus
- Cigarette smoking
These are known as major risk factors. Other minor factors include :
- Sedentary lifestyle
- Unhealthy dietary habits such as consumption of high saturated and trans fats
- Drinking alcohol above safe limits
Genetics, age, sex and race also predispose to atherosclerosis. It is more common after the fourth decade and males are more prone than women.
The effects of atherosclerosis includes the deposition of a plaque that hardens and thickens over time. This causes a gradual narrowing of the lumen of the artery. Blood flow is therefore gradually diminished. The target organ has a reduced blood supply and may shrink to some extent due to less oxygen and nutrients. It also undergoes a type of tissue injury known as ischemia.
There is a risk of the a sudden obstruction of the blood supply if a blood clot blocks the remaining space in the artery lumen. This can cause tissue death (ischemia). Apart from the target organ, the artery itself can be severely affected. The artery walls weaken and balloons (aneurysm). Over time this aneurysm can rupture with often fatal consequences.
Prevention is the best cure in the case of atherosclerosis and is largely aimed at making lifestyle changes and controlling the risk factors. Avoid alcohol and cigarette smoking. Adopt a more active lifestyle by doing regular physical exercise in any form is helpful. A low fat diet is ideal. Certain drugs are prescribed when the condition is significant or there is evidence of atherosclerosis-related diseases.
- Statins can help to correct the high cholesterol levels.
- ACE inhibitors help bring down blood pressure levels.
- Aspirin in low doses or clopidogrel prevent clot formation
Invasive treatments such as coronary angioplasty or coronary artery bypass surgery, stenting may be done for advanced cases to break or dissolve the clots in blood vessels.