Electrocardiography was an invention of the early 20th Century. A Dutch physicist and Nobel Prize winner, Willem Einthoven, not a physician, adapted a newly discovered electrical instrument. This instrument, the string galvanometer, was applied to medicine to record the minute changes in electrical current produced by the human heart, the electrocardiogram (ECG). Early electrocardiograph instruments were quite large and bulky, expensive to own, and appeared first in major medical centers and research laboratories. By the end of World War I, the electrocardiogram had more than proven its value and became the cornerstone of modern clinical cardiology. As technological improvements were further applied to medical instrumentation, it became possible to do ECG's as often as necessary, even in doctors' offices. Electrocardiographic monitoring over time became possible, leading to the eventual establishment of Coronary Care Units in hospitals.

In the early 1940's safe and effective methods of cardiac catheterization were developed, allowing measurement of blood flows and pressures inside the heart, and visualization of the working of the heart by x-rays. This greatly accelerated the surgical treatment of heart conditions, especially congenital anomalies, and valvular problems. With more advanced techniques allowing actual catheterization of coronary arteries, atherosclerosis as it affected the coronary arteries was open to investigation. The space program contributed by encouraging miniaturization of electronic equipment, and by computer advances. Computer enhanced imaging techniques, first applied to pictures taken from space, are now routinely incorporated in the computer-assisted images produced during arteriography, Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI) scanning.

It became obvious that there was a group of diseases that were characterized by abnormalities in arteries. These were arteries that became hardened, inelastic, and lined with a substance containing cholesterol, fatty substances, and calcium. This disease of the arteries was noted with heart problems, stroke, kidney failure, and high blood pressure. It was erroneously assumed earlier that these diseases were the cause of high blood pressure. It has turned out to be more complicated than that…

What are Risk Factors?
Importance of Treatable Risk Factors
The concept of "risk factors" came about from the observations of doctors as the treated their patients. Why did some patients develop heart attack, stroke, and other diseases of arteriosclerosis, while others did not? It was partly due to heredity, but could not be explained solely on that basis. Many individual reports began to show patterns that could be suspected, but not proved statistically. For instance, there was, and is, a much higher incidence of heart attack in men than in women. The incidence of heart attack and stroke also rose, with the increasing age of the individual. The "risk factors" which doctors became concerned about through observation were family history of heart disease, blood cholesterol level, high blood pressure, cigarette smoking, diabetes, heart size, and electrocardiographic abnormalities.

Advancing age, male sex, high blood pressure, cholesterol and other lipids, diabetes, obesity, physical inactivity, electrocardiographic abnormalities, family history, heart enlargement, stress; all these things have been implicated as "risk factors" in coronary heart disease and other arteriosclerotic diseases. Lack of estrogen, or estrogen deficiency in women has been associated with increased risk of cardiovascular disease. This is has been noted in post menopausal women. However, the use of hormonal oral contraceptive medications has been associated with increased risk of heart attack in women, especially those who also smoke cigarettes. The interactions and relationships among these factors, and their relative importance, are still being studied and debated.

Many doctors 40 or 50 years ago minimized the effect of blood cholesterol because they felt cholesterol and calcium plaques that narrowed blood vessels were only a disease present in old age. During World War II, and in the Korean War of the early 1950's, many American servicemen were killed in action. A number of these young men, including teenagers, had postmortem examinations, or autopsies. Pathologists were surprised to find, in very young adults, many more cholesterol deposits in the arteries, including the coronary arteries of the heart, than they would have imagined. These were the young All-American boys who had grown up eating hamburgers, steak, French fries, hot dogs, chocolate candy, milkshakes, apple pie, and ice cream. This brought an awareness that arteriosclerotic changes, and the risk factors that predispose to the disease, must be operating from childhood. This created some urgency to identify these risk factors, so a preventive program and treatment could be devised.

One of the most famous medical research studies ever organized had been started in a small town near Boston, Massachusetts, called Framingham, in 1948. The Framingham Heart Study consists of long-term surveillance of large groups of people over time. Data have been derived from this study for more