Circulation disorders

The complex network of arteries, veins and capillaries that carry blood from the heart, through the systemic circulation and through the lungs, can be regarded as one of the most hard-working systems of the body. Despite its extraordinary strength and resilience, however, it is subject to various disorders, many of which are due, in part at least, to essentially mechanical problems, often associated with aging of the tissues, but sometimes with other factors that seem to make such natural degeneration significantly – perhaps avoidably – worse.

The principal disorder affecting the tissues of the circulatory system is known as arterial disease – more specifically as arteriosclerosis. It is the cause of more deaths among the adult populations of developed countries than any other single factor: most heart attacks are in fact due to disorders of the arteries supplying the heart rather than to disease of the heart tissue itself.

Arteriosclerosis occurs when the tissue of the artery walls become less elastic, thicker or otherwise damaged. All these can cause the lumen of an artery to narrow, which reduces the blood flow and may lead to the artery becoming blocked by a blood clot. When this occurs it is called a thrombosis. A coronary thrombosis occurs when a blood clot in a coronary artery prevents blood reaching the muscles of the heart. A stroke, or cerebral thrombosis, occurs when a clot blocks one of the blood vessels in the brain, leading to the rapid death of the brain tissues deprived of their blood supply. Thrombosis can also occur in blood vessels in other parts of the body, such as the veins in the legs, and if it does, local tissue damage can result.

A particular form of arteriosclerosis, called atherosclerosis, occurs when fatty deposits, called atheromas, develop in the inner layers of the artery walls. This is believed to be due to a defect in the body’s fat metabolism, but is also thought to be associated with an excess of certain types of fat – particularly saturated fats rich in cholesterol – in the diet. The fatty deposits thicken the artery walls and also reduce their elasticity, narrowing the artery and making a blockage, or occlusion, more likely.

Although the specific causes of arterial disease are not known, certain things do seem to increase the likelihood of it developing. Diet, and particularly a diet rich in animal fats, seems to be an important contributory factor; others include a high dietary salt intake, smoking and high blood pressure. Ways to minimize the risk of developing arterial disease include avoidance of such contributory factors, as well as losing excess body weight and taking regular gentle exercise. Because of the hormonal effects of stress on the circulatory system, this is also a possible risk factor, and avoiding stress, or learning how to relax between periods of extreme stress, may also reduce the risks. Experiments with drugs that inhibit clotting, such as coumarin, may also prove beneficial, although results cannot yet be regarded as conclusive.