Introduction
An adult heart is made mainly out of cardiac muscle and needs to pump blood through blood vessels which are equivalent to 50,000 miles long. To do this it needs a good supply of blood and glucose. Cardiac muscle cells get their supply from coronary arteries. If one of these arteries were to become blocked then essential nutrients would not reach the heart as the blood supply would be reduced. This would interfere with the heart muscle’s ability to contract.
The narrowing of the arteries by decomposition of fatty material on the wall is called arteriosclerosis, the direct result of this being a lowered blood flow. This reduced blood flow is a progressive condition and may have been occurring many years before symptoms start to show. The triggers for the deposition which will damage the endothelium lining of the artery are associated with carbon monoxide (which is a product of smoking), high blood cholesterol levels, high blood pressure and diabetes mellitus. These factors are synonymous with bad diet and poor health, which consequentially results in an increased risk in heart disease.
The body’s natural response to this damage is monocycles attaching to the lining of the artery. These monocycles will penetrate between the endothelium cells and inside the tunica media, where they develop into macrophages, which will accumulate the fatty materials such as cholesterol and triglycerides. The smooth muscle cells begin to reproduce in response to the growth substances the macrophages produce. The overall result of this is the development of a clump of fatty material covered by a smooth muscle and fibrous tissue on the inside of the artery; this is known as an atherosclerotic plaque.
The exact mechanism of the plaque formation is not fully understood but studies of epidemiology, the pattern of occurrences, of atherosclerosis show that factors occurred with producing the atherosclerotic plaque are: Smoking, diet, obesity, high blood pressure (known as hypertension), heredity factors, high blood cholesterol levels and diabetes mellitus. If the fibrous caps of these atherosclerotic plaques are thin they can rupture and cause a thrombosis; a clot triggered by the expulsion of fatty materials from the ruptured atherosclerotic plaque. This clot can grow in minutes and the artery can be completely blocked.
Although all organs of the body require a blood supply, some more than others and some need a continuous flow. Muscles, for example, especially if they are not being used, remain unharmed even when they are deprived of their blood supply for many minutes, whilst an interrupted blood supply to the brain can cause malfunctions within seconds causing loss of consciousness and if the flow of blood is not restored within a few minutes then irreversible damage can be the result. The heart itself, much like the brain, is dependent on a constant supply of blood. If the heart loses its blood supply, this is known as ischaemic, its ability to pump blood around the body is seriously reduced. This ischaemic heart disease is the cause for most heart attacks. The heart cells duly die causing a heart attack or a cardiac infarction. If this clot is in the brain then the person has a stroke.
Risks and Preventions
- Age & Gender: As you get older, your risk for CAD increases.
- Men have a greater risk of CHD and develop it earlier.
- Risk increases after age 45.
- In women, risk increases after age 55.
Inheritance:
- People with parents who suffered CHD are more likely to develop it themselves.
- People of certain races are at risk especially if they are the minority in the country in which they live.
- Diabetes Mellitus: diabetes greatly increases the chances of developing CHD and strokes.
Risk Factors That Can Be Avoided
- High blood cholesterol: cholesterol is a type of lipid. When passed in the blood they are combined with proteins to create lipoproteins. There are two types of lipoproteins;
- Low-density lipoproteins (LDL): these contain high levels of cholesterol and are more dangerous that high-density lipoproteins, which have, low levels of cholesterol.
It is recommended that a person should keep their blood cholesterol level below 200mg per 100cm3 of blood to reduce risk of developing coronary heart disease. (Euan, 49)
High blood pressure: Short terms increased in blood pressure are standard but steady high blood pressure in a person at rest becomes a severe medical condition called hypertension. It can lead to an increased risk of CHD because an artery increases the thickness of the muscle in response to the rising blood pressure. This makes the lumen narrow which decreases the blood flow to the heart. High blood pressure can be prevented by losing weight, cutting down on salt intake, decreasing alcohol consumption and quitting smoking. (Fred, 57) Overweight or obesity: people who carry overload weight body fat are more probable to develop CHD even if they have no other risk factors.
Lack of physical activity: moderate exercise can help to reduce blood cholesterol, blood pressure and obesity. Cigarette smoking: smokers are more four times as probable to build up CHD, particularly if they smoke cigarettes, than none smokers. The following materials in tobacco are thought to contribute to the risk.
Medication
- Glyceryl Trinitrate – this drug causes “rapid dilation of the blood vessels and so improves the supply of oxygen to the cardiac muscle” (Fred, 57). Dilation of this kind enlarges the lumen in arteries hence giving the blood more room to flow past fatty build-ups (atheroma) under less pressure. This drug provides a fast relief from the symptoms of Angina, but it does not stop MI.
- Calcium antagonists – these “dilate arteries and arterioles by preventing calcium ions moving into the smooth muscle cells” (Robert, 493). Therefore there is less resistance of blood flow in the coronary arteries. Calcium antagonists are for constant use and are prescribed when a patient suffers from acute angina, making a simple walk across a room impossible. They do not work as quick dilators like Glyceryl Trinitrate does.
Surgical Treatment
- Balloon Angioplasty – scientifically known as Percutaneous Transluminal Coronary Angioplasty. This technique was pioneered in the 1970s. A catheter is inserted in to an artery in the leg and when treaded up through the body to the aorta, where it is fed down the coronary artery affected by an atherosclerosis build-up. A balloon is then inflated, compressing the build-up to the walls of the artery and allowing normal blood flow to resume.
- Heart bypass there are four main arteries supplying the heart with blood; the left coronary artery, the right coronary artery, the left circumflex and the left anterior descending. If a 100% blockage occurs in any of these major arteries then it is often necessary to bypass it. The procedure is complicated compared to balloon angioplasty, however if successful the patient can enjoy a much increased quality of life – in many cases bypass surgery can save the patient’s life. In the procedure veins are taken from either the legs or arms and sewn to the aorta and the sewn back beyond the blockage of the affected coronary artery. Depending on how many arteries have an atherosclerosis build up, the patient may require double, triple or even quadruple bypasses to bypass all the damaged arteries.
Works Cited
Euan Ashley A., Niebauer Josef. Cardiology Explained. London: Remedica 2004: 45-50.
Robert A. O’Rourke, R. Wayne Alexander. Hurst’s The Heart, Manual of Cardiology. New York, McGraw Hill Inc., 2004: 493-514.
Fred C. Pampel, Seth Pauley. Progress Against Heart Disease. Connecticut, Praeger, 2004: 55-57.