Heart, blood, and circulatory disorders

Arterial disease, and in particular arteriosclerosis, causes more deaths than any other disease in Western countries. The most common heart disease is actually due to diseased coronary arteries rather than to heart tissue itself. Damage or degeneration of these arteries reduces the blood supply to heart muscle, which ceases to function as a result. Other disorders can affect the rhythm of the heart, the valves, or the muscle directly. The heart can also be affected by general infections such as rheumatic fever, by cancer, usually as a secondary rather than a primary site, and by disorders such as high blood pressure (hypertension), which in turn may result from external factors such as smoking, lack of exercise, and fatty diet.

Over the past 30 years, the treatment of heart disease by surgery has advanced astonishingly. The use of heart-lung machines has enabled the heart to be stopped during operations. Implantation of artificial pacemakers and valves is now routine. Even heart transplant operations are becoming more successful, although all the problems have not yet been solved.

Valvular heart disease may be treated by an operation to replace the disordered valve with an artificial one. First the patient’s heart is by-passed by a heart-lung machine (A), the aorta clamped, and an incision made (B) to expose the diseased valve, which is removed. The replacement is lined up with long stitches (C), which are then drawn tight. Finally all incisions are closed (D). The photograph (right) shows an artificial heart valve stitched into its final position.

Arteriosclerosis

Arterial disorders are particularly dangerous because they affect the blood flow and so can cause damage to the heart, brain, and other parts of the body. With advancing years arteries and their walls become thickened (arteriosclerosis), and fatty material is laid down in the lining (atheroma), narrowing the vessel. Symptoms are unusual before middle age, though studies on American soldiers killed in Vietnam showed the presence of the disease as early as the late teens.
Several factors significantly increase the risk of developing arterial disease: smoking, high blood pressure, the amount of fats (lipids) in the bloodstream, diabetes, and aging. Diet can also affect blood pressure and blood lipid content.

If the surface of an atheromatous plaque is ulcerated, continuous healing and scarring tends to produce an ever-constricting arterial “bottleneck.” Partial blockage in the flow of blood causes symptoms of ischemia (reduced local circulation) in the part of the body supplied by the affected arteries. Symptoms vary accordingly, but in the leg, for example, calf muscle pain may be caused by brief exercise and relieved by resting. If coronary arteries are affected, the symptom is chest pain (angina pectoris), which is particularly likely to occur when walking uphill in cold weather. An atheroma that causes ischemia in a kidney, in contrast, results in increased blood pressure.

Thrombosis

As the ulcerated plaque heals, local blood clotting may occur. If the clot (thrombus) blocks the artery completely, the effects are likely to be immediate and dramatic. In the heart, such blockage (occlusion) prevents blood reaching heart muscles, causing a heart attack (myocardial infarction). Unless the blood flow can be restarted quickly, the muscle dies. In the brain, arterial occlusion results in a type of stroke known as a cerebral infarct. In the legs, total loss of blood supply causes gangrene as tissue dies.

Even if such a clot does not block the artery completely, part of it (an embolus) may break off, travel in the circulation, and lodge in smaller arteries. Blockage may last for a short time only before the clot is broken down. If such a vessel is one of the network supplying the brain, short lived symptoms, such as loss of consciousness, limb weakness, or difficulty with speech, may occur. This is described as a transient ischemic attack (TIA).

Arteriosclerosis is a disorder in which fatty deposits accumulate in an artery, narrowing it and restricting the flow of blood. The artery also loses its elasticity and suppleness. The diagram shows sections of normal and sclerotic arteries. Severe arteriosclerosis may so narrow a vessel that a blood clot forms. The photograph shows a section of an affected coronary artery that carries blood to the muscles of the heart itself.

Aneurysms

Progressive damage to an artery wall can lead to weak points where the vessel wall bulges, producing an aneurysm. The aorta is commonly affected, and if so, may rupture, causing catastrophic hemorrhage. Aneurysms in cerebral vessels compress the surrounding brain tissue, producing various symptoms according to the part of the brain that is affected.

Treatment of arterial disease

The treatment of arterial disease is divided into prevention of clinical symptoms by slowing the progress of the disease, and repair of damaged vessels after symptoms have developed. Arterial damage can probably be minimized if the risk factors can be controlled by not smoking; by avoiding certain fats (particularly animal fats) in the diet; by treating hypertension; through weight loss; and by reduced salt content in the diet. Psychodynamic methods such as biofeedback, meditation, or other means of reducing stress may also be useful, or drug treatment may be necessary.

Exercise, for instance jogging, cycling, or cross-country skiing, improves the blood supply to the heart and muscles, reducing the risk of damage from occlusion of a single artery. People who exercise regularly tend to reduce or avoid smoking and lose excess weight, thereby lowering blood lipid levels and blood pressure.

Because many of the adverse effects of arterial diseases are related to thrombosis, there is great interest in the possibility that agents that inhibit clotting may reduce the progression of the disease. For instance, aspirin in low doses can inhibit platelet aggregation (stickiness), which is part of the clotting process.

Primarily, however, treatment for arterial disease is surgical. Usually, an occluded artery is opened and the atheromatous area is removed. The arteries commonly treated in this way are the carotid arteries in the neck, which supply the brain, and the femoral arteries, which supply the legs.
Diseases of the coronary arteries may be treated either by surgery or with drugs, depending on the exact sites of obstruction and the individual patient’s symptoms. The most common surgical procedure is the coronary artery by-pass graft, in which segments of vein taken from the legs are connected to the aorta and the coronary artery to by-pass the area of occlusion. Surgery is also sometimes required to repair areas of dead muscle after myocardial infarction, especially when the muscular wall (septum) between left and right ventricles has ruptured, or when the muscle controlling the mitral valve is torn.

Two new forms of therapy for coronary artery disease have been developed recently. One employs a thin tube (catheter), which is passed along a coronary artery until a narrowed segment is reached; a balloon on the end of the catheter is then inflated to dilate the constriction. In the other, used if a coronary artery has been obstructed very recently by thrombosis, a clot-dissolving enzyme can be injected into the arteries using a catheter. If this is done within a few hours of coronary thrombosis, heart muscle death can be prevented.

Venous thrombosis

Blood may clot in veins because of damage to the vein wall, poor blood flow, or abnormally thick blood. It is more common in women than men, and particularly in those taking the contraceptive pill. The vein affected is almost always in a leg, which becomes red, swollen, and painful.

Treatment is with anticoagulants, especially heparin. In some cases, part of the clot breaks loose and travels to the lungs, where it obstructs the blood flow. This is called pulmonary embolus and is also treated with anticoagulants. If the clot is large enough to block the main pulmonary vessels, the condition can be fatal.

Varicose veins

Varicose veins also occur most commonly in the legs. They are dilated veins that form when the valves that normally control the pressure in the vessel are damaged. This may be due to obstruction of the veins during pregnancy, trauma, or gradual deterioration through aging. In the elderly, damaged veins may lead to the formation of varicose ulcers, especially around the ankles.
Treatment may be with elastic stockings, which help compress the vessels; with injections to thrombose small veins leading into the varicosed ones, in order to reduce the blood flow through them; or by surgical removal (stripping) of the affected vessels.

Fast-growing and malignant, leukemia cells are stained purple here so that they show up in a sample of blood from a patient with this pervasive form of cancer, which can spread through the circulatory system. There are various types of leukemia, most of which originate in the bone marrow and other blood-forming tissues. Some respond to chemotherapy using drugs that selectively destroy the cancerous cells. Exposure to radioactivity or X rays has been identified as a possible cause.

Heart diseases and disorders

Congestive heart failure occurs when the heart muscle cannot pump enough blood for the body’s needs. This is usually caused by the gradual replacement of heart muscle tissue by fibrosis. The condition can be partially relieved by drugs, such as digitalis, which strengthen the remaining muscle fibers, and by diuretics, which reduce the accumulation of blood.

The rhythm of the heart may be abnormal in many ways. The most extreme occurs when the muscle contracts in a completely uncoordinated way (fibrillation). The patient will die within minutes unless cardiac massage or electric shock (cardioversion) is applied. Pacemakers implanted surgically and a variety of drugs may control other arrhythmias.

Heart valves may be damaged by rheumatic fever or by a process similar to arteriosclerosis that affects them directly. In either case, the valve may become too small (stenosis) or leaky (regurgitant). Treatment is to replace the diseased valve with an artificial one by surgery. Some congenital abnormalities may also need surgical treatment.

Blood diseases and disorders

The red cells in the blood carry oxygen; a deficiency of red cells (anemia) produces symptoms such as fatigue and lethargy because insufficient oxygen reaches the tissues. Dietary deficiencies of iron, vitamin B]2, or folic acid are the commonest causes. Anemia is especially common during pregnancy, because the fetus uses the mother’s reserves. It can also occur as a result of prolonged blood loss, commonly a result of a stomach ulcer or very heavy menstruation, or as a symptom of certain cancers of the digestive tract. Treatment is to replace the missing dietary factor or to treat the cause of blood loss.

An excess of red blood cells (polycythemia) makes the blood thicker than normal and therefore less able to flow through smaller blood vessels. The disease, particularly common in smokers, increases susceptibility to strokes, transient ischemic attacks, and venous thrombosis.
White blood cells are part of the body’s defense mechanism and increase in number during infections. White-cell deficiency is rare, but is found in patients treated with cytotoxic drugs against cancer, or following adverse drug reactions. Abnormal white cell production occurs in leukemia, a form of cancer affecting white blood cells.

Infection of the blood is called septicemia, and generally spreads from a local infection such as an abscess or a wound. Treatment is with antibiotics.

Although blood required for transfusion is kept sterile, certain viral or virus like infections are transmitted by transfused blood nevertheless. At least two types of hepatitis can be transmitted in this way. So can AIDS (acquired immune deficiency syndrome), which can also be transmitted by means of body fluids, such as semen. In AIDS, the balance of different types of white cells in the body is altered, leaving the individual susceptible to unusual infections and certain rare cancers.
Once very rare in America, malaria is now becoming more common as increasing numbers of people travel abroad. It is a blood disorder caused by a parasite that enters the blood from a mosquito bite. The parasite * breeds in red blood cells, which then burst to release the offspring, causing symptoms of fever, shivering, and aches. Various drugs are used to prevent the disease but resistant forms are becoming more common.