Coronary heart disease (also known as coronary artery disease) is actually a disease of the arteries that supply the heart with blood and nutrients. A diagnosis of coronary artery disease is made if any artery is 60% occluded. A heart attack, or myocardial infarction (death of heart muscle tissue), occurs when an obstruction or spasm disrupts or terminates blood flow to a portion of the heart muscle. The amount of heart muscle damage is determined by the location of the obstruction or spasm and the speed with which medical intervention is begun. Heart attacks of any magnitude produce irreversible injury and myocardial tissue death. It usually takes 5 to 6 weeks to form a fibrous scar around dead cardiac tissue. This area of dead tissue can no longer contribute to the pumping of blood, resulting in a less efficient heart. Massive heart attacks that cause extensive muscle damage result in death.
Although most heart attacks occur after the age of 65, the dysfunctions leading to them often begin before adolescence. These processes are insidious and often go undetected until, without warning, a heart attack occurs. The attack is sudden but the circumstances leading to it are long standing. In fact, there is considerable evidence that the silent phase of coronary heart disease has pediatric origins.
The ongoing framingham study, which began in 1949, identified the risk factors connected with heart disease. Cigarette smoking, high blood pressure, elevated cholesterol levels, diabetes, obesity, stress, physical inactivity, age, gender, and family history were found to be highly related to heart attack and stroke. As the risks were discovered, the realization evolved that heart disease was not the inevitable consequence of aging or bad luck but an acquired disease that was preventable. After a few years, researchers realized that preventive efforts should begin in childhood, and more years passed before they investigated the prevalence of these risks among children and adolescents.
Autopsy studies of 18 year olds have shown a positive relationship between blood cholesterol levels and the prevalence of fatty streaks on the walls of the coronary arteries and aorta. The evidence indicates that the average cholesterol level in children in overfed, under exercised societies such as the united states is too high.
High blood pressure has been reported in children as young as 3 years of age, and blood pressure levels generally continue into adulthood. 4 Almost 19% of high school seniors smoke cigarettes daily, and the use of smokeless tobacco products has increased substantially among 17 to 19 year old men. An estimated one in five youngsters between the ages of 5 and 17 years are substantially overweight; that is, a minimum of 20% above their desirable weight.
Autopsy studies of american combat battle casualties, whose average age was 22 years, in the korean and vietnam wars showed obstructions in the coronary arteries. Native korean and vietnamese soldiers had clean and open arteries. These obstructions are caused by atherosclerosis, which is a slow, progressive disease of the arteries that can originate in childhood. It is characterized by the deposition of plaque beneath the lining of the artery. Plaque consists of fatty substances, cholesterol, blood platelets, fibrin, calcium, and cellular debris that anchor to a roughened site in the artery. Several theories have been advanced regarding the development of rough spots in arteries, but whatever the trigger, the smooth muscle cells beneath the lining erupt and form a network of connective tissue that eventually becomes plaque. Plaque enlarges over many years beneath the linings of arteries, causing them to narrow. The affected portion of the myocardium becomes ischemic (lacking sufficient blood flow). This eventually leads to two possibilities. First, bleeding may occur in the plaque, or second, a blood clot may form on the surface of the plaque. In either case, a heart attack or stroke may occur if the arterial channel is shutdown as a result. The atherosclerotic process is responsible for 80% of the coronary heart disease deaths in the united states.
As many as one third of all heart attacks are imperceptible to the victim. These events usually involve small areas of the heart muscle and may go unnoticed unless verified by an electrocardiogram (ECG). The ECG remains abnormal for about 72 hours after a silent heart attack. If the diagnosis is not made during this time, it will probably be missed. The typical heart attack is very noticeable, and the symptoms are overt.
Atherosclerotic lesions are more likely to form where single arteries branch into two smaller arteries. Vessel diameters reduce where branching occurs. This increases blood turbulence, which produces greater damage at these sites. This combination of events renders these sites more vulnerable to injury and the development of plaque. This phenomenon may occur in the arteries leading to the brain, kidneys, lungs, and legs, as well as the heart.
Coronary heart disease may be delayed or prevented by keeping the risk factors associated with heart disease in check. Most can be modified and controlled through appropriate lifestyle behaviors.
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