What is Coronary Heart Disease (CHD)?
Lycette Clarke 5/9/2007
What is Coronary Heart Disease (CHD)?
CHD has two principal forms - angina and heart attacks (myocardial infarction). Both occur because the arteries carrying blood to the heart muscle become blocked or narrowed, usually by a deposit of fatty substances, a process known as arteriosclerosis. Angina is a severe pain in the chest brought on by exertion and relieved by rest. A heart attack is due to obstruction of a coronary artery either as a result of arteriosclerosis or a blood clot: part of the heart muscle is deprived of oxygen and dies.
Basic diagram of the heart as a system
Diagrams from: http://www.pbs.org/wgbh/nova/eheart/human.html
The blockage of the arteries with the excess plaque formed by smoking, alcohol consumption, age (as you get older your risk factor increases) and diet, sex (males are more likely to get CAD), hereditary and the combined contraceptive pill and fat intake
http://www.heartcenteronline.com/myheartdr/common/articles.cfm?ART
This diagram shows the build up of a blockage in an artery. This is most due to the build up of colestral and fats that deposit on the wall of the artery. Colestral is a waxy fat (lipid) which is carried through the blood by lipoproteins. The two main types of lipoprotein, high-density lipoproteins (HLDs) and low density lipoproteins (LDLs)
HLDs (good colestral) carry LDLs (bad colestral) away from the artery walls. LDLs stick to artery walls and can lead to plaque build-up, or arteriosclerosis
Risk factors leading to Coronary Heart Disease
Cigarette smoking, raised blood cholesterol and high blood pressure are the most firmly established, non-hereditary risk factors leading to CHD with cigarette smoking being the "most important of the known modifiable risk factors for CHD", according to the US Surgeon General. A cigarette smoker has two to three times the risk of having a heart attack than a non-smoker. If both of the other main risk factors are present then the chances of having a heart attack can be increased eight times. At least 80% of heart attacks in men under 45 are thought to be due to cigarette smoking. At this age, heavy smokers have 10 to 15 times the rate of fatal heart attacks of non-smokers.
Even light smokers are at increased risk of CHD: a US study found that women who smoked 1-4 cigarettes a day had a 2.5-fold increased risk of fatal coronary heart disease. (Willett, 1987). Other factors include being male, age, having close relative who have had heart attacks being overweight, taking to little exercise, having high blood pressure and eating too much salt or saturated fat or too little fibre. Cigarette smoking increases LDL and decreases HDL levels, raises blood carbon monoxide (and could thereby produce endothelial hypoxia), and promotes vasoconstriction of arteries already narrowed by atherosclerosis. It also ...
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Even light smokers are at increased risk of CHD: a US study found that women who smoked 1-4 cigarettes a day had a 2.5-fold increased risk of fatal coronary heart disease. (Willett, 1987). Other factors include being male, age, having close relative who have had heart attacks being overweight, taking to little exercise, having high blood pressure and eating too much salt or saturated fat or too little fibre. Cigarette smoking increases LDL and decreases HDL levels, raises blood carbon monoxide (and could thereby produce endothelial hypoxia), and promotes vasoconstriction of arteries already narrowed by atherosclerosis. It also increases platelet reactivity, which may favour platelet thrombus formation, and increases plasma fibrinogen concentration and Hct, resulting in increased bloods thickness
The relation between fat intake and the risk of coronary heart disease is not fully understood, however it does seem clear though that a high level of saturated fats and cholesterol in the diet is associated with an increased risk of coronary heart disease.
Heart attacks and other forms of coronary heart disease (CHD) result in approximately 500,000 deaths annually accounting for 25 percent of the Nation's total mortality. Research has revealed an association between moderate alcohol consumption1 and lower risk for CHD. This Alcohol Alert reviews Epidemiologic evidence for this association, (BMJ 2003; 326:1379-1381 (21 June), Ever D Grech) explores lifestyle factors and physiological mechanisms that might suggest ways to explain alcohol's apparent protective effects, and presents available data on the balance between alcohol's beneficial and harmful effects on health. An association between moderate drinking and lower risk for CHD does not necessarily mean that alcohol itself is the cause of the lower risk. For example, a review of population studies indicates that the higher mortality risk among abstainers may be attributable to shared traits other than participants' nonuser of alcohol Substantial evidence has discounted speculation that abstainers include a large proportion of former heavy drinkers with pre-existing health problems (i.e., "sick quitters"). Nevertheless, health-related lifestyle factors that correlate consistently with drinking level could account for some of the association between alcohol and lower risk for CHD. Among the most widely studied of these factors are exercise and diet.
Few studies have adjusted for subjects' levels of physical activity, despite evidence that exercise protects against CHD occurrence and mortality. In a comprehensive review of published studies, Berlin and Colditz concluded that risk for CHD was proportionately lower at higher exercise levels. Measures of activity level vary among studies.( PE and the study of sport) Studies evaluate factors such as job-related physical requirements, frequency of participation in unspecified sports, estimated vigorousness of given activities, calculations of energy expended, and tests of cardiovascular fitness. Results of a community survey indicated that the prevalence of regular exercise was higher among moderate and heavy drinkers than among non-drinkers. Regular exercise was defined as any form of no occupational physical activity performed at least three times per week. The role of exercise in the alcohol-CHD association requires additional study.
Diet is one of the strongest influences on CHD-related death among men ages 50 to 70. International comparisons, laboratory data, and prospective studies suggest that diets high in saturated fat and cholesterol increase the risk for CHD. Epidemiologic data suggest that moderate drinkers may consume less fat and cholesterol than heavier drinkers and abstainers, potentially accounting for a portion of the lower CHD risk associated with alcohol. However, results of other prospective studies indicate that alcohol's association with lower CHD risk is independent of nutritional factors
The risk of coronary arteriosclerosis increases with age, but evidence suggests that the condition may start to develop very early in life. About four out of five people who die of coronary heart disease are age 65 or older. At older ages, women who have heart attacks are more likely than men are to die from them within a few weeks.
Women before menopause rarely suffer from heart disease Coronary heat disease mainly afflicts adult males and manifests itself in the middle ages. Diet individuals with hereditary high levels of blood cholesterol are more prone to develop coronary heart disease. The risk of coronary heart disease rises as blood cholesterol levels increase. When other risk factors (such as high blood pressure and tobacco smoke) are present, this risk increases even more. A person's cholesterol level is also affected by age, sex and heredity.
Smoking tends to increase blood cholesterol levels. Cigarette smokers also have raised fibrinogen levels and platelet counts, which make the blood stickier. Carbon monoxide attaches itself to haemoglobin much more easily than oxygen does. This reduces the amount of oxygen available to the tissues. All these factors make smokers more at risk of developing various forms of atherosclerotic disease. As the atherosclerotic process progresses, blood flows less easily through rigid and narrowed arteries and the blood is more likely to form a thrombosis. This sudden blockage of an artery may lead to a fatal heart attack, a stroke or gangrene.
High blood pressure: increases the heart's workload, causing the heart to enlarge and weaken over time. It also increases the risk of stroke, heart attack, kidney failure and congestive heart failure. When high blood pressure exists with obesity, smoking, high blood cholesterol levels or diabetes, the risk of heart attack or stroke increases several times.
Weight: People who have excess body fat - especially if a lot of it is in the waist area - are more likely to develop heart disease and stroke even if they have no other risk factors. Excess weight increases the strain on the heart, raises blood pressure and blood cholesterol and triglyceride levels, and lowers HDL ("good") cholesterol levels. It can also make diabetes more likely to develop.
Coronary heart disease is much more common in some families than in others. As DNA determines the sizes of the arteries themselves it is probable that characteristics of the heart are passed on to offspring.
Lack of exercise: regular exercise aids a healthy circulation, and the physically inactive are more at risk from heart disease
Other diseases: diabetes and high blood pressure increase the risk of coronary disease. Diabetes seriously increases the risk of developing cardiovascular disease. Even when glucose levels are under control, diabetes greatly increases the risk of heart disease and stroke. About two-thirds of people with diabetes die of some form of heart or blood vessel disease.
Socio-economic disadvantage: as nations become prosperous coronary heart disease becomes less of a problem for the well educated classes, and preferentially affects those in the lower social levels; poor housing and little education are strong indicators of high coronary mortality
Psychological and personality factors: sleep disturbances and stress are predictors of angina, infraction and death due to heart attacks.
Birth control pills mean that the higher doses of oestrogen and progestin, increase a woman's risk of heart disease and stroke, especially in older women who smoked heavily. Newer, lower-dose oral contraceptives carry a much lower risk of cardiovascular disease, except for women who smoke or have high blood pressure. If a woman taking oral contraceptives has other risk factors (and especially if she smokes), her risk of developing blood clots and having a heart attack goes up. It rises even more after age 35.
The tendency of risk factors to cluster in a single individual is being increasingly recognized. Obesity and physical inactivity contribute importantly to the development of multiple risk factors in the American population; this clustering of multiple metabolic risk factors is called the metabolic syndrome. Risk will be further accentuated in smokers with several metabolic risk factors. There is an increasing need to identify persons with multiple risk factors and, because of their high risk, to initiate management directed at all risk factors.
Bibliography
? http://www.heartcenteronline.com
? http://www.bizone.co.uk
? British medical Journal: BMJ 2003; 327:97-100 (12 July), Ever D Grech,
BMJ 2003; 326:1379-1381 (21 June), Ever D Grech
? Sport and PE
? PE and the study of sport
? British Heart foundation, angina information booklet,
? After the heart attack booklet,
? It'll never happen to me leaflet and booklet.
? Congenital heart disease
? Smoking article biomedical sciences, vol 10, issue 1
Sep 1997
