HUMAN DISEASES (Part 3 of 7)

Heart Rhythm and Pacemakers

A node of special cells in the heart controls its rhythm by regularly producing energizing electrical signals. Sometimes, abnormal signals cause extra heart beats, or tachycardia.

At other times, especially in older persons, the signals might not be conducted too well through the heart, thus slowing it. When a person's heart rate drops below 40 beats a minute, he usually feels faint and cannot function well. In that case, he often can be fitted with an artificially powered heart pacemaker.

Diagnosis and Treatment of Heart Trouble

A doctor carefully questions and examines anyone suspected of heart trouble for evidence of pain, fatigue, abnormal heartbeat, and so on. He listens to the heart and lungs with a stethoscope. Sometimes, a heart murmur, a rushing noise heard through the stethoscope, provides a clue to a heart problem. A faint murmur can be normal, but a loud one usually indicates a diseased heart valve or other trouble. A chest X ray is usually taken to get a picture of the heart and lungs. An electrocardiogram reveals the electrical activity of a patient's heart.

A doctor can also rely on cardiac catheterization and angiography to diagnose heart disease. Cardiac catheterization involves slipping a catheter, a long tube, through veins into the heart to learn such things as how much blood the heart is pumping, whether its valves are damaged, and whether it is contracting as it should. Angiography involves injecting dye through a catheter into the heart so that subsequent X rays will reveal the internal anatomy of the heart and the blood flow through it.

Rheumatic fever, inflammatory disease probably caused by bacterial infection; damages connective tissue of the heart and joints.

Rheumatic Heart Disease

Rheumatic heart disease has both an acute form and a chronic form. The acute form, rheumatic fever, inflames joints and heart muscle. The joints always recover, but if the condition becomes chronic the heart valves may eventually become scarred. Rheumatic fever most often affects the mitral, or bicuspid, valve of the heart and produces a blockage called mitral stenosis.

Rheumatic fever is a health problem in many of the world's developing nations. It is caused by an unusual body response to an infectious sore throat sparked by the bacterium beta haemolytic streptococcus. Uniquely, the bacterial cell wall and the human heart muscle have a protein in common. A person with a "strep" throat develops antibodies against the bacterial protein. However, the antibodies may also attack that person's own heart muscle, damaging it over the years. Penicillin and other antibiotics treat strep throat and can prevent heart damage. In severe cases after many years, however, surgery might be needed to repair or even replace a damaged heart valve.

Hypertensive Heart Disease

Hypertension, or high blood pressure, is a fairly common disorder. Ordinarily, the heart creates sufficient pressure to send blood throughout the body. However, sometimes resistance to blood flow from the arteries is high and the blood pressure rises above normal. Because the heart must then work harder to maintain the higher pressure, it enlarges.

Blood pressure is maintained by means of a complex interaction between the heart, the nervous system, and a kidney hormone called renin. Some persons with hypertension have too much renin in their blood. High blood pressure increases the wear and tear on blood vessels. It also can cause heart failure, strokes, and kidney disorders. When discovered soon enough, it can be treated with drugs.

Other Kinds of Heart Disease

Sometimes the heart does not develop properly and a child can be born with a serious congenital heart disease. Heart valves might be too narrow or missing altogether, or the septum, a wall separating the heart chambers, might be incomplete. As a result, a hole exists between the heart chambers. Such congenital heart diseases can be discovered by means of cardiac catheterization and angiography and often can be corrected by a heart surgeon.

Some substances are dangerous to the heart. For example, diphtheria bacteria produce a toxin that damages the heart. Excessive alcohol drinking weakens and enlarges the heart.

Persons with heart murmurs caused by faulty valves or congenital heart disease are susceptible to endocarditis, a bacterial infection of the inner lining of the heart. Also, certain viruses can cause myocarditis, inflammation of the heart muscle, and pericarditis, inflammation of the outer lining of the heart.

Blood Vessel Disorders

Thrombus, blood clot that remains attached to place of origin in blood vessel.

Atherosclerosis, the thickening and hardening of arterial walls, may occur in many arteries. Cholesterol and other fats that form in the process obstruct the affected arteries and, at times, produce a thrombus, or clot, in them. Sometimes, these clots break away, especially from the heart, and embolize, or travel to some other part of the circulatory system.

There, they can block a blood vessel and keep oxygen away from a vital body part.

Embolism in the brain, for example, can cause a stroke.

Aneurysm, bulging and thinning of some point in the wall of a blood vessel (usually an artery) or of the heart because of arteriosclerosis ("hardening of the arteries"), embolism, infection, or physical injury; element common to all true aneurysms is injury to the media; after the aneurysm has developed it tends to grow, with danger that the vessel wall will rupture; treatment of aneurysm involves surgical removal of the diseased section of artery and its replacement with a plastic graft.

Aneurysm occurs when the walls of a large artery, especially the aorta, become weak and balloon out. Atherosclerosis can cause an aneurysm. So can syphilis. The venereal disease can also make the aortic valve leak.

Varicose veins, bulging veins in the leg, develop when the walls of the veins weaken. The condition may be inherited or may stem from phlebitis, an inflammation of the veins.

Phlebitis may trigger clots in the veins, which sometimes break away, travel to the lungs, and form a pulmonary embolus. Drugs used to prolong clotting time often correct clotting disorder.

CANCER AND OTHER GROWTH DISORDERS

Cancer the collective name for any of the dangerous tumours, or growths, that can arise in the body is the second ranking cause of death in the United States and Canada. It claims more than 460,000 lives each year in the United States; some 87,000 each year in Canada.

There are more than 100 different kinds of cancer.

Cancer is characterized by rampant, abnormal cell growth. If this occurs within a vital organ or tissue, normal function will be impaired or halted, with possibly fatal results.

Cancer called sarcoma can arise in muscle, bone, connective tissue, blood vessels, and fatty tissue.

Cancer called carcinoma can arise in skin cells and in cells that line the body's cavities and organs. Abnormal proliferation of white blood cells is called leukaemia An aberrant tumour in the body's lymphatic tissue is a lymphoma. Cancer can strike many parts of the body.

Some cancerous tumours are fast growing; they may double their size within a month or so. Others are slow growing and may not spread for many months or even years.

The Cancer Process

Tumours, or neoplasms, are purposeless bulges of excessive cell growth in tissue. If they are local and harmless, they are benign. If they can spread to other tissues and cause the body harm, they are malignant. Malignant tumours are cancerous.

Cell multiplication goes on normally in the human body for replacement of dead cells, but in cancer the multiplication goes somehow awry. Local malignant tumours often can be removed by surgery, thus ending the problem. However, if the cancer cells are not destroyed by surgery or other means, they may metastasise, or leave the local site and spread to other parts of the body. When they do metastasise, the entire body can succumb to the disease.

Cancer is believed to begin with one wildly multiplying cell in a given tissue. The process so resembles the action of cells in an embryo as they divide and shape the body that scientists think that cancer is tied in with the basic chemistry of the cell. After the embryonic cells have performed their tasks, certain chemical repressors lock up portions of DNA in genes in the cell nucleus.

These repressed pieces of DNA no longer trigger the biochemical reactions associated with rapid embryonic cell division. Thus, the seeds of cancer might be in everyone's body.

Then, at some time in the future, an event such as virus infection, radiation intake, inhalation of a carcinogen, or cancer-causing chemical, or an imbalance of hormones might free the genes and permit a mature body cell to revert back to an embryonic like cell. One theory even holds that the gene-bearing chromosomes of normal cells have certain sections capable of making virus like particles. These particles could then infect neighbouring cells and make them produce more particles, until many cells were proliferating wildly.

Tumour angiogenesis factor (TAF), substance that causes rapid growth of tiny blood vessels.

Cancer cells produce antigens against which the body reacts with antibodies. Small pockets of cancer cells, called silent cancers, might constantly be springing up in a person's body, only to be destroyed by the body's immunity system before they could do any harm. If the antibodies are ineffective, however, the cell mass grows to the size of a pinhead. Unless it gets enough blood, the pinhead mass will not get bigger. However, such tumours can give off a substance called tumour angiogenesis factor, which "fertilizes" rapid growth of tiny blood vessels into the tumour Then, it starts growing again because it has an ample supply of food from the blood. When it grows large enough to interfere with a vital body activity, the sufferer dies.

Treatment of Cancer

Cutting out the cancerous tissue through surgery is probably the most effective way of fighting cancer, as long as it has not had a chance to spread. Radiation treatment using radioactive cobalt or radium salts is another method of inhibiting the spread of cancer.

Certain anticancer drugs hinder the growth of cancer cells and prevent their spread.

CANCER SIGNS

There are seven warning signs of cancer. If you notice any of these symptoms be sure to call them to the attention of a physician:

1. A sore that does not heal.

2. A lump or thickening anywhere in the body.

3. Nagging hoarseness or cough.

4. Unusual bleeding or discharge.

5. Persistent indigestion or difficulty in swallowing.

6. A change in bowel or bladder habits.

7. A change in a wart or a mole.

Early detection of cancer through annual physical examinations has been effective in reducing cancer death rates. In its early stages, cancer can often be stopped before it spreads.

Surgery performed early enough can remedy most women suffering from cancer of the uterus or cancer of the ovaries. A simple test, called the Pap smear, given by a physician at regular intervals can indicate the presence of precancerous uterine tissue before it becomes dangerous.

Lung cancer, which is often linked with cigarette smoking, affects males more than any other type of cancer; and it is spreading rapidly among female smokers as well. The next most frequent type among males is prostate cancer. Cancer of the breast is the leading type of cancer among females. Cancer of the colon/rectum ranks second. A woman can frequently discover breast cancer herself before it becomes serious by regular examination of her breasts for lumps.