Cardiac Disease | Research & Encyclopedia Articles

Cardiac Disease

Throughout history, diseases of the heart have captured the concern and interest of investigators. Ancient Greek and Roman physicians observed the serious and often fatal consequences of heart disease. But effective treatment for heart disease was limited to rest and painkillers until the eighteenth-century discovery of the therapeutic properties of the foxglove plant, whose dried leaf is still used to make the medicine digitalis.

While the heart was once considered a part of the body that could never be improved surgically, the twentieth century has seen a revolution in surgical treatment for heart disease. Blocked coronary arteries can be bypassed using new tissue and failing hearts can be transplanted. Yet heart disease remains the primary cause of death in the United States. Preventive health measures, such as improved diet and regular exercise, have become fundamental tools in the battle against heart disease.

In the twentieth century, physicians acquired the tools to prevent heart disease in some cases and treat it effectively in many others. Major medical advances, such as the development of antibiotic therapy in the 1940s, have dramatically reduced heart disease due to syphilis and rheumatic fever. Developments in surgery, new drugs, diagnostic skill, and increasing knowledge about preventive medicine have also greatly reduced deaths from heart disease. Between 1980 and 1990, the death rate from heart disease dropped 26.7% in the United States, according to the American Heart Association (AHA).

Congenital heart disease, the atrial-septal defect in particular, was first described in 1900 by George Gibson of Edinburgh. This problem, which occurs when there is an opening in the wall (or septum) between two atria, can cause the right ventricle to be overwhelmed with blood, a condition that eventually leads to heart failure. In some cases, however, the holes are small and do not cause problems. For years, there was little physicians could do to help children with the problem. The development of successful surgical procedures to repair atrial septal defects was one of a multitude of dramatic modern advances in heart surgery.

New types of surgery were made possible with a series of technological advances. In 1934, the American John H. Gibbon developed a machine that allowed the heart to stop beating during surgery while the blood was oxygenated outside the body. Gibbon spent nearly 20 years testing the machine on animals. In 1953, Gibbon became the first surgeon to operate on an open heart when he repaired an 18-year-old girl's atrial septal defect.

With new access to the heart, the treatment of heart disease changed dramatically. The development of the first electric pacemaker in 1950 enabled doctors to correct many arrhythmias (abnormal heart rhythms) and numerous types of heart block (a conduction disorder of the heart's electrical signals). In 1992, a total of 113,000 pacemakers were implanted in the United States, according to the American Heart Association.

A significant change in the treatment of coronary heart disease was the development of coronary bypass surgery in 1967 in the United States. The surgery uses blood vessels taken from elsewhere in the body, often the leg, to pass around diseased tissue. By 2001, over half a million coronary artery bypass grafts were performed yearly in the United States, according to the AHA.

Another commonly performed procedure for individuals with coronary heart disease is angioplasty, during which narrowed arteries are stretched to enable blood to flow more easily. The surgery involves threading a tube through the body and stretching the artery by using a plastic balloon that is inflated when the tube is in the coronary artery. A total of 399,000 angioplasty procedures were performed in 1992, according to the AHA.

The most dramatic change in treatment of heart disease was the development of methods to replace the most damaged hearts with healthy human hearts or even animal hearts. The first successful human heart transplant was performed by South African surgeon Christiaan Barnard in 1967. The patient, however, died in 18 days. Though many surgeons tried the operation, success was limited, most patients dying after days or months, until the early 1980s, when effective drugs were developed to fight organ rejection. In 1993, a total of 2,300 heart transplants were performed in the United States, where the one-year survival rate is 81.6%, according to the AHA.

Physician William Osler observed in 1910 that certain types of people were most likely to develop coronary artery disease, particularly individuals who were "keen and ambitious." Contemporary efforts to prevent heart disease focus on identifying types of behavior and activity that increase the risk of heart disease and on encouraging individuals to adopt healthier lifestyles.

The massive body of evidence linking various types of risk factors to heart disease derives from a series of ambitious twentieth-century studies of heart disease in large groups of people over a long period of time. One of the best known of these efforts is the Framingham study, which has traced thousands of residents since 1949. This and other studies have led to findings that individuals are at a greater risk of heart disease if they have high levels of certain types of cholesterol in the blood, if they smoke cigarettes, if they are obese, if they have high blood pressure, and if they are male. Blood cholesterol, a fat-like substance found in all human and animal tissue, is a primary focus of efforts to prevent heart disease. High cholesterol levels are shaped, in part, by diet and can be lowered. Experts suggest limiting consumption of foods high in saturated fats, such as cream, meat, and cheese. Such a diet reduces the risk of high levels of low-density lipoprotein, or LDL, the type of cholesterol which increases the risk of heart disease.

Exercise has also been promoted as a protection against heart disease. Numerous studies have shown that individuals who do not exercise are more likely to develop coronary heart disease. Exercise reduces blood pressure and eases blood flow through the heart. In addition, people who exercise are less likely to be overweight.

Individuals who burn more calories are also more likely to have higher levels of what has been called the "good" cholesterol--high-density lipoprotein, or HDL. This type of cholesterol is believed to reduce the risk of heart disease. Other activities that boost the level of HDL include maintaining average weight and not smoking cigarettes.

The last few decades of the twentieth century have also seen the introduction of numerous drugs that prolong life and activity for individuals with heart disease. Beta-blockers are used to treat angina, high blood pressure, and arrhythmia. They are also given to individuals who have had heart attacks. These drugs block the neurohormone norepinephrine from stimulating the organs of the body. This makes the heart beat more slowly and slows the dilation of certain blood vessels.

Another important class of drugs for the treatment of heart disease is the vasodilators, which cause blood vessels to dilate, or increase in diameter. These drugs, including the so-called ACE inhibitors, are used to ease the symptoms of angina by easing the work of the heart, to forestall complete congestive heart failure, and to prolong life in people who have had heart attacks.

A third important type of drug reduces cholesterol in the blood. The process by which these drugs eliminate cholesterol from the blood varies, but several work by preventing the reabsorbtion of bile salts by the body. Bile salts play a role in digestion, and they contain cholesterol.

Diagnostic advances have also made a difference in the treatment of heart disease. Cardiac catheterization enables doctors to see how the heart works without surgery. The process, which was first explored in humans in 1936, involves sending a tube through an existing blood vessel and filling the tube with a contrast material that can be tracked as it circulates through the heart. In 1992, a total of 1,084,000 of these procedures were performed to diagnose heart problems.

Though knowledge about the treatment and prevention of heart disease has expanded dramatically, heart disease remains an immense threat. A total of 925,000 Americans die each year of cardiovascular disease, a general category including heart disease, stroke, and high blood pressure, all of which are linked. The biggest killer is coronary heart disease, claiming almost 500,000 U.S. deaths each year.

Genetic therapy for heart disease is considered a fertile area for progress. In 1994, surgeons performed a procedure on a woman who had a genetic defect that prevented her liver from removing adequate amounts of LDL cholesterol. She had suffered a heart attack at age 16. The procedure, which took place in Michigan, involved the insertion of genetically modified cells in her liver, to enable the organ to remove LDL cholesterol properly. With the new cells, her heart should no longer be threatened by high levels of cholesterol.

Though much is known about risk factors for heart disease, new theories will continue to be tested in the future. For example, various studies have shown that individuals who eat large amounts of fish (especially containing particular oils called omega-3 fatty acids) or who consume vitamin E have a lower than average rate of coronary heart disease. Ambitious studies are under way to confirm or deny this information.

Researchers are also looking carefully at women and heart disease, a topic that has been overshadowed by research concerning men and heart disease in the past. Estrogen supplements are known to reduce the risk of heart disease in women, but extensive studies have not been conducted. The National Institutes of Health (NIH) is currently funding a long-term study of 27,000 women who will either take estrogen, progesterone, or a placebo. These women will then be evaluated for heart disease and other indicators. Such studies will help document what may and may not be helpful to women seeking protection from heart disease.

In 1998, the American Heart Association published its third list of what it considers to be the most promising research areas in heart disease. These included: gene therapy which could potentially encourage the growth of new blood vessels to and from the heart, thus bypassing diseases vessels; the discovery of new "super aspirins" which seem to have even greater protective effects for both heart attack and stroke; more data to support the association between inflammation and heart attacks; better techniques for early detection of obstructed vessels in the heart (using magnetic resonance imaging, or MRI); hope that damaged left ventricular muscle can regain better functioning, if a mechanical device called a left ventricular assist device (LVAD) takes over the work of the left ventricle for a time; further evidence that tobacco is a crucial risk factor in the development of heart disease, as evidenced by research which showed that as few as 10 cigarettes a day shortens life; more research supporting the importance of diet and exercise on levels of cholesterol in the blood; efforts to encourage people to seek treatment more quickly when a heart attack is suspected; the association between non-responsiveness to nitric oxide, and the development of high blood pressure.

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