What is atherosclerosis?
Atherosclerosis is a condition where elasticity of the arterial walls are lost leading to hardening and narrowing of the artery reducing the blood flow. It is also known as arteriosclerosis. Most of the time it is the build up of fatty plaques in the wall of the artery that leads to this narrowing (sclerosis). There is risk of clot (thrombus) formation completely occluding the narrowed artery or clot dislodgement and subsequent lodging and blockage of a different artery. These are common causes of a heart attack (myocardial infarction) or stroke (cerebrovascular accident).
Atherosclerosis can progress without any symptoms over decades. The lack of symptoms should not detract from the fact that its long term complications can be deadly due to reduced blood supply or complete obstruction of an artery. It can be treated and managed over long periods of time thereby reducing the risk of these often fatal complications. However, a person will always be at risk once the condition first develops and needs to be monitored regularly.
What are the symptoms of atherosclerosis?
Initially atherosclerosis is asymptomatic (silent). With progression of disease different symptoms appear depending upon the organs whose blood supplies have been affected.
- Heart: initially chest pain occurs (angina pectoris) with exertion and relieved with rest, due to reduced blood supply. Without intervention it can lead to complete stoppage of blood supply to a particular region of the heart (due to clot formation) causing heart attack (myocardial infarction).
- Brain: initially with reduced blood supply via cerebral arteries there is temporary weakness of limbs (upper and lower), slurring of speech, sudden black out (transient ischemic attack, TIA). Without treatment brain stroke can occur as blood supply is hampered due to clot formed in the brain or formed elsewhere (like the heart) but lodged in the cerebral arteries.
- Arms and legs: weakness, pain, numbness in the limbs can occur when the supplying arteries are affected.
- Kidney: atherosclerosis in the renal arteries can lead to high blood pressure
- Atherosclerosis in the arteries supplying the genitals can cause erectile dysfunction in males and loss of libido in females.
What causes atherosclerosis?
The exact cause of atherosclerosis is unknown but the most popular hypothesis states that LDLs (a type of lipid containing only cholesterol) are deposited in the arterial wall and are oxidized by free radicals to toxic substances. The body responds to this change by recruiting special blood cells (WBC) to digest the oxidized LDL. The WBC after ingesting the oxidized LDL becomes foam cells and eventually ruptures releasing cholesterol in blood and repeating the same cycle. Thus in the arterial wall lipid deposits (plaque) are formed. The plaque consists of three layers
- Innermost yellowish soft material (cholesterol)
- Macrophages (WBC)
- Deposition of hard calcium at outermost layer
These lesions can become unstable (liable to rupture) triggering clot formation. There are other possible causes of atherosclerosis like infection by cytomegalo virus (CMV) and herpes virus but the lipid theory seems to explain the disease process in most people.
- Advancing age
- Sedentary life style
- High blood pressure
- Cigarette smoking
- High blood cholesterol
- Family history
- Intake of high fat diet
How is atherosclerosis treated?
Life style modification is favored, whether drugs are prescribed or not. This includes cessation of smoking, regular exercise, weight reduction and diet low in saturated fats. Medication is prescribed in moderate to severe cases and should be used in conjunction with lifestyle changes. These drugs include :
- Statins: cholesterol lowering agents.
- Low dose aspirin: prevents clot formation.
- Beta blockers, ACE inhibitors, calcium channel inhibitors.
- Other drugs for associated diseases: anti-hypertensive and ant- diabetic agents in particular.
- Angioplasty and stenting, bypass surgery done for atherosclerosis of coronary artery.
- Thrombolytic therapy (reteplase): to dissolve a clot in brain (stroke) and heart (heart attack).