The physiology and anatomy of the cardiovascular system is most intricate. And, since the whole body depends on the circulation of the blood as a means of sustaining life, any minor alteration in anatomy or function is of vital importance. There is a multitude of conditions which may impair the central cardiac system. Of primary import are those infections which may damage the inner moving parts of the heart, and those conditions which overstrain the work of the heart. The body has certain innate protective measures which guard against any damaging forces which attack the heart. The situation of the heart in the body is sufficient protection against most outer dangers. Infections are combated by the same body responses which react to fight the attacking germs in other tissues. And automatic adjustments in the dynamics of the fluid system occur to improve the efficiency of the circulation during exertion.
Valvular Heart Disease. Yet in some instances the protective forces are not sufficient. In some infectious forms of heart disease the germs or their toxic products leave the valves of the heart scarred and deformed so that they cannot function properly. This is valvular heart disease. Physicians can tell by the use of a stethoscope during examination if the heart valves function normally; in addition to the normal sounds of the valves snapping closed may be heard additional vibrations, or the normal sounds may be replaced by abnormal ones. All abnormal sounds are called murmurs. The sounds of each valve are heard maximally at a specific site on the chest, so the physician can easily distinguish the sound of each valve. Valvular disease may be of the type where the valves do not close sufficiently, or where they do not open adequately. In the former type some of the blood is actually forced backward in the system with each beat. This is termed valve insufficiency, and in layman’s language is often referred to as “leakage of the heart.” Failure of the valves to open properly does not allow the adequate flow of blood out of the heart chamber with each beat, and is called valve stenosis. In either case the heart works inefficiently. To keep the tissues supplied, the heart must work harder than normal for even ordinary activity, and with added exertion the tissue demands may be more than the heart can deliver. Of the infectious forms of heart disease, rheumatic fever is the greatest offender, and it is one of the foremost crippling illnesses of today.
There are several other less common infections of the heart, such as endocarditis (inner- heart-inflammation) and pericarditis (outer- heart-inflammation).
Congenital Heart Disease. This form of heart disease is that which is present since the time of birth due to defective development of the heart. Such defects may be in the heart itself or in the large vessels which lead directly off the heart. In recent years surgical correction of some type of deformities have been possible. The interference of such defects with the ability of the heart to perform its work act similarly to valvular disease impairments.
Toxic Heart Disease. In toxic heart disease the heart is stimulated to function at a faster rate for long periods of time and often overcompensates so that the rhythm is entirely upset. The stimulation may result from the toxin’s direct action on the organ, or from the body’s efforts to rapidly eliminate the toxin. In most cases this is precisely a disturbance in cardiac physiology and not accompanied by anatomical alteration, so the system often is reverted back to normal with elimination of the offending toxin. As examples, this form of heart disease may occur in hyperthyroidism (overactive thyroid gland) and uremia (kidney wastes in blood).
Disturbances in Cardiac Rhythm. These comprise another group of cardiac diseases. For centuries the heart has been considered the seat of the emotions, and many such disturbances are merely manifestations of emotional conflicts. Certainly the stress of modern life plays a major role in predisposing to overwork of this structure. And when organic changes are present, the added insult from emotional influences may precipitate disease which otherwise would never have manifested itself. But there are also conditions wherein there is actually tissue change causing the disturbance in rate and rhythm of the heart. More often this malfunction is a consequence of another disease rather than a primary disease in itself.
The initiation of each beat of the heart is relayed by nerves from the brain just as in any other structure. The heart is also provided with an intrinsic mechanism of its own for co-ordinated action between both upper chambers (right and left atrium) and both lower chambers (right and left ventricle). The atriae contract first by impulse from extrinsic nerve source. As these upper chambers contract, the impulse is conducted within the heart wall to the lower chambers, and their action follows. If the heart wall has been damaged by a disease process, this normal relay of impulses is interrupted, and the harmony between the upper and the lower halves is upset. This is called heart block, and as a result the atriae and the ventricles beat independent of one another, with markedly impaired circulation.
Vascular Disease. Vascular disease (that is. disease of the blood vessels) can give rise to heart disease. The mechanism of cardiac involvement is essentially by an increased resistance in the vascular tree against which the heart must work. When the arteries have lost their elasticity through arteriosclerosis (artery hardening), there is little yield in volume of the vascular system to accept the blood the heart expels with each thrust of a beat. When the smaller vessels remain constricted with a small lumen, the heart has to pump with greater pressure to drive blood through to the capillaries in the tissues; this is high blood pressure, a major medical problem of today. And when a shunt between an artery and a vein exists, some of the oxygenated blood finds its way back to the lungs before giving up its oxygen, and some of the nonoxygenated blood is allowed to reach the tissues, so that a more rapid transport is required to keep the tissues supplied. All such conditions make the heart work harder in performing its function of pumping blood to all cells of all organs of the body.
Coronary Heart Disease. Such disease entails an involvement of the blood vessels which supply the heart itself with blood. The heart is a muscle, and unlike other muscles it functions every moment of every hour without rest, but like other muscles it requires oxygen and other nutriments as fuels in order to contract. Such is supplied to the heart through vessels which lead off the main artery system (see Fig. 105), just as any other organ has a special blood supply route. But in this case, any impairment of circulation is more vital, since life itself is contingent on this organ. Many tissues can tolerate a lack of oxygen for relatively long periods and still survive, but the heart is forever working and requires a constant supply.
General terms for impairment of the coronary circulation are coronary insufficiency or coronary occlusion. Such may result from such things as a blood clot formation within the vessel, called coronary thrombosis; or from hardening of the vessels’ walls, coronary sclerosis. Coronary artery disease is of greater and greater import. With prolongation of the life expectancy of man by reduction of deaths from many diseases, this disease becomes more prevalent as more people reach older age. The surgical field has little to offer against this disease.
Blood Diseases. Blood diseases, such as anemia, often lead to heart disease, by necessitating a greater circulation rate because the blood cannot carry the normal amount of oxygen. Thus, more trips back to the lungs are required to keep the tissues supplied. Greater demand is placed on the heart.
Heart Failure. The result of almost all forms of heart disease if they progress untreated is heart failure. This expression perhaps is a misnomer, but it has been used for decades to designate the condition which results if the heart fails in its function of transporting sufficient blood to all tissues. Not only must the heart deliver sufficient blood to the tissues, it is also responsible for relaying the forces which return the blood to the central system for more oxygen.
The blood must circulate continuously through the entire circuit. If the heart’s action is not of sufficient force to pump the blood all the way around the circuit, there is a tendency for the stagnation of blood in the peripheral tissues. When the heart fails to get the blood out of the peripheral tissues, they may suffer nutritional and oxygen wants, for the fresh blood cannot enter. Abnormal fluid exchanges occur with the delayed flow through the capillary beds, and fluid collects in the tissues. This condition, called edema, occurs most frequently in the capillary beds of the lungs, feet, and abdomen, but may involve other areas. The result is called congestive heart failure.
The heart is a muscle. Like any other muscle, when put to excessive use, it enlarges and strengthens itself in order to be able to perform the increased demands placed on it. This is but one of the several compensatory measures the cardiovascular system is able to make to meet increased circulatory demands in the very active individual, or the person with a circulatory defect. The demonstration of an enlarged heart in a person is evidence that that heart is laboring under abnormal strain. It is one of the earlier signs of cardiovascular disease. Shortness of breath from congestion of the capillary beds in the lungs or from general oxygen wants of the body, and edema, are other indications.
Heart disease is one of the foremost diseases of today. This is primarily because it is a disease of older people, for the most part, and more people are living to older ages. In more rccent times, the prevention of infectious diseases which cripple the heart have been brought under control, to a certain extent, and a greater understanding of conditions which overstrain the heart has been apparent. Nevertheless, this group of diseases is responsible for the greatest number of deaths each year in the United States. Many research and educational programs have been organized to help bring heart disease under greater control.
In the surgical patient, coincidental heart disease does not necessarily add greatly to the operative risk, provided that it is treated concurrently with the surgical treatment. In the past it had more frequently been necessitated to forego operation because of co-existing heart disease, but today fewer operations need be denied on this account. Frequently the operation is delayed to determine the cardiac reserve (that is, evaluate the functional capacity of the heart). Physical examination is often aided by functional tests and special examinations, such as electrocardiography. After treatment of the heart condition has been inaugurated, there is usually but little increased risk in operation. Often no specific therapy is required. A person whose heart has sufficient reserve capacity to enable him to carry on normal daily routines without limitations can safely undergo major anesthesia and operation.
Heart disease complicates surgery only in so far as it modifies the usual treatment plan. The patient requires careful evaluation before and all through the surgical program, and certain steps in the management may require modification. Often an internist or a cardiologist is engaged to care for the cardiac patient in co-operation with the surgeon. But the instances where necessary surgery is precluded by heart disease are becoming less frequent. The average patient after special cardiac preparation suffers little more strain from the anesthetic and the operation than he would experience from normal daily activity.
Often the individual’s general health is improved and the outlook on life made brighter by the surgical correction of some disabling condition. Moreover, the correction of a source of constant ill health may even improve the heart status. To be sure, heart disease complicates surgical management, but seldom complicates the results.