Atherosclerosis
Topic Highlights
' Atherosclerosis is a hardening of arterial walls and a narrowing of arterial lumen caused by the gradual build up of plaque on the inner walls of the arteries.
' This presentation details the formation of plaque in arterial walls, the complications that follow, and treatment options.
Transcript
Atherosclerosisis the single most important cause of coronary heart disease. Atherosclerosis derives its name from the Greek words 'athero,' meaning paste, and 'sclerosis,' meaning hardness. It is the hardening and the narrowing of the arteriescaused by the slow build-up of plaqueon the inside walls of the arteries. Plaque is formed by the build-up of cholesterol, calcium, and other substances found in blood.
Cholesterol is a substance produced by the liver. Animal products are rich sources of dietary cholesterol. Cholesterol is carried in the blood by two major lipoproteins: low-density lipoproteins(LDL) and high-density lipoproteins(HDL). HDL is also called the 'good' cholesterol and LDL the 'bad' cholesterol. This is due to the fact that HDL helps deliver cholesterol to the liver from the body, including the arterial wall, whereas LDL, delivers cholesterol from the liver to cells in the body - an excess of which is deposited in the arterial wall.
Once the cholesterol requirement of the cells is met, the extra cholesterol may build up along blood vessel walls as plaque. People with high levels of LDL are at increased risk for atherosclerosis, since they deliver more cholesterol to artery walls. On the other hand, higher levels of HDL protect against atherosclerosis.
There are two types of plaque: hard and soft. Hard or stable plaques have relatively thick fibrous caps. Soft or unstable plaques are vulnerable to rupture without warning. When the soft plaque bursts, it triggers the formation of a thrombosisin the artery at the site of the rupture and restricts the flow of blood, causing a potential larger block in the lumen.
Some risk factors for atherosclerosis cannot be modified, such as advancing age, gender, family history and menopause. Advancing age is strongly associated with atherosclerosis and heart disease. Atherosclerosis is more common in males until middle age, after which the risk becomes equal between both sexes. Individuals with a family history of cardiovascular diseaseare at a greater risk when compared to those without. Menopause in women increases the risk, possibly due to decreased levels of estrogen.
The major modifiable risk factors are high blood cholesterol levels(the optimum level of total cholesterol < 200, optimum level of HDL > 60, optimum level of LDL below 100), diabetes mellitus, hypertension, cigarette smoking, alcohol consumption, lack of physical activity/exercise and obesity. Increased levels of low-density lipoproteins (LDLs) (or bad cholesterol), decreased levels of high-density lipoproteins (HDLs) (or good cholesterol) and high levels of triglyceridesin the blood increase the risk of atherosclerosis and heart disease.
High blood pressure or hypertension is a major risk factor for atherosclerosis. Sometimes symptoms may not be evident at all. Angina, or a heart attack, may be the first sign of atherosclerosis.
A physical examination followed by blood tests to check the levels of cholesterol may reveal the presence of atherosclerosis. There are various other diagnostic tests to find the location and severity of atherosclerosis.
Some of the tests done to diagnose coronary heart disease include an Electrocardiogram(ECG), an Echocardiogram, a stress test, a Nuclear Scan or Thallium scan, Electron beam CTand Coronary angiography.
The treatment involves an all-around approach by assessing the extent and severity of the disease, identifying the risk factors, management of the symptoms and evaluation of existing treatment to improve the life expectancy and quality of life in high risk patients. Treatment also includes lifestyle changes, medication and sometimes, invasive procedures and surgery.
Lifestyle changes are mainly directed to decrease the risk factors related to atherosclerosis, the most important cause of heart disease. These include maintaining healthy weight to height ratio, quitting smoking and alcohol consumption, regular exercise, decreasing sodium content in food and consuming a low-fat, low-cholesterol diet to maintain an ideal LDL to HDL ratio.
Cholesterol lowering agents help bring down the cholesterol levels to normal. This helps control one of the risk factors of atherosclerosis. Examples are atorvastatin, pravastatin, simvastatin, fluvastatin, lovasatatin, and rosuvastatin, etc.
The most widely used invasive treatment to treat coronary heart disease is percutaneous coronary intervention(PCI) (also called percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass graft surgery (CABG).
Balloon angioplasty or PTCA is a relatively new procedure invented by Andreas Gruentzig. It is a non-surgical procedure that removes coronary artery blockages. The procedure is done with a small balloon catheter inserted into an artery in the groin or arm, and passed into the blockage in the coronary artery. The balloon is then inflated several times to enlarge the narrowed artery.
The chance of reblockage of the artery is about 30% in which case the patient would need a repeat procedure or a CABG. To prevent this a stent may be inserted into the artery at the blockage. The stent is placed at the tip of the catheter, over the balloon. When the catheter reaches the blockage, the balloon is inflated, expanding the stent. Then the balloon is deflated and removed along with the guidewire and catheter. The stent is left in the coronary artery to prevent it from getting blocked again.
In CABG the surgeon will bypass the blockage using grafts. One end of the graft is attached to the aorta and the other to the coronary artery beyond the blockage. The surgery is done by many methods.
Changes in lifestyle help manage coronary heart disease. It is important to exercise regularly, have regular check ups to monitor blood pressure and watch for complications of hypertension. Stress levels should be managed effectively and prescribed medications taken regularly.