There is a multitude of conditions which may impair the central cardiac system. Many of these are now correctable by surgical procedures, and in the last few years the number of conditions which may be benefited by surgery has increased. For the purposes of this book, heart disease may be divided into acquired heart disease and congenital heart disease. The former is that which develops in a previously normal system from a disease process during life; the latter is a heart defect which has been present since birth.
Congenital heart disease is that which has been present from birth due to defective development of the heart. It cannot be within the scope of this work to discuss in detail the development of the heart in the embryo and fetus. Suffice it to say, in the embryo and prenatal infant numerous shunts and short-circuits and extra pathways are necessary for the oxygenation of all tissues of the unborn infant. Before birth all oxygen is acquired by circulation between the infant and the placenta (afterbirth). In this structure occur exchanges of gases, whereby the waste products are diverted to the mother’s blood stream and the oxygen absorbed into the infant’s. After birth, the various shunts and extra pathways normally obliterate since they are no longer needed; and if they remain they may be harmful rather than beneficial. In certain cases of congenital heart disease these short-circuits do not obliterate. Most of these short-circuits are between the systemic and the pulmonary sides of the circulation. The two sides of the circulation are not completely separated as they normally are. The oxygenated and unoxygenated blood becomes mixed in the central circulatory system. Therefore the blood pumped out to the tissues may not be completely oxygenated. This gives rise to the condition commonly referred to as “blue baby.” The circulatory system is not normal and works under a handicap.
In acquired heart disease the majority of lesions are of the heart valves. In congenital heart disease the defects frequently involve the great vessels leading to and from the heart. In many forms of congenital disease there is more than one abnormality; these may be within the heart or abnormal communications between the great vessels.
The results of an impaired central circulatory system have been discussed under the heading Heart Failure. The same changes occur in those types of heart disease which may be correctable by surgery. A failing circulation may of course modify any surgical procedure, including those on the heart itself.
ACQUIRED DISEASES OF THE HEART
The heart requires a constant supply of oxygen and nutriments to perform its continuous pumping action; it receives this normally through the coronary vessels which lie over the heart muscular wall. In coronary heart disease this blood supply is deficient. This may be from decrease in size of the caliber of the vessels by coronary spasm; by hardening of the coronary vessels (coronary sclerosis); or by blood clot in the vessels (coronary thrombosis). Treatment for this condition is usually with medical measures directed at increasing the caliber of the coronary vessels, decreasing the heart’s oxygen demands, and relieving clot formation. However, more lately several surgical procedures have been advocated which are designed to direct more blood to the heart muscle. The results of some of these methods appear promising.
Internal mammary artery ligation is a method wherein an artery which stems close to the origin of the coronary arteries is tied off. This directs more blood into the coronary stream to increase the flow to the heart. The procedure is a relatively minor one, usually performed under local anesthesia, through a small incision between two ribs just to the side of the breast bone. Currently the procedure is of debatable value among various advocants.
Internal mammary transplant is an operative procedure directed at increasing the blood supply to the heart by transplanting into the heart muscle an artery which lies between the heart and the rib cage (internal mammary artery). This is a major chest operation, and again its definitive value is sometimes questionable—that is, it is not applicable to all cases of coronary heart disease.
Pericarditis induction is another surgical procedure designed to increase oxygen supply to the heart muscle. This operative procedure is designed to induce inflammation of the pericardium, the sac encasing the heart. Whenever inflammation is produced, there is increased blood supply by increase in the caliber and number of capillaries (as seen in the studies of inflammation). When the inflammation is induced, the oxygenation to the area is increased. Essentially the procedure involves opening the pericardial sac and placing within it an irritating foreign body substance, such as talcum; the pericardium is closed and the foreign body inflammatory reaction ensues. This is a major operative procedure applicable to some forms of coronary insufficiency diseases.
Other surgical means of increasing the blood supply to the myocardium have been advocated. Many are currently in their investigative stages, some with seemingly encouraging applications.
Valve stenosis has been mentioned and its resultant circulatory impairments studied. In this condition the valve is scarred and does not open sufficiently; the heart must work harder to force the blood out of the partially obstructed chamber. Any one of the four heart valves may be affected, but some are involved more frequently than others. (Congenital stenosis may also occur, usually in conjunction with other heart and great vessel defects.) Operation is most effective in accomplishing a cure in many cases. The operation may be by closed cardiotomy or open cardiot- omy, the latter method more recently of greater effectiveness. The valve leaflets may be operatively amended (valvulotomy), or the scarred areas between the valves severed (commissurotomy). Major preoperative studies and preparation are necessary for this formidable operative undertaking.
Valve insufficiency (valve regurgitation) is discussed with the resulting circulation impairment. Any valve may be so affected. The heart labors under a strain as the blood leaks back into the chamber through the incompetent valve. The heart must work harder to maintain circulation. Like any other muscle doing excessive work, the heart enlarges in attempts to become a stronger pump. Valve insufficiency is most often a result of rheumatic fever. Some valve stenosis may be associated.
Valve insufficiency has more recently been attacked surgically by open cardiotomy. Various tissues have been transplanted to replace the diseased valve leaflets, such as fascia, segments of arteries and veins, and other pliable tissues. Artificial devices have been employed; plastic artificial valves have been designed which replace the diseased valve. This field of work has met with success and further advances seem promising. At present modern methods are applicable to many cases of this serious disease.
Pericarditis is an inflammation of the pericardium, the sac which encases the heart. The disease may be acute or chronic, the latter often associated with other diseases. Pneumonia, tuberculosis, spreading cancer, and metabolic disturbances may cause pericarditis as a part of such diseases. Complete body survey and extensive laboratory tests may be necessary to isolate the exact cause so that specific treatment may be instigated. Various physical signs may suggest the disease, but x-ray, fluoroscopy, EKG, circulation pressures, blood tests, and bacterial studies are usually necessary. Acute pericarditis may become chronic. As the disease progresses, excessive fluid may accumulate in the pericardial sac, the condition known as pericardial effusion. There results interference of the heart filling as the heart is crowded by the fluid; circulation is impaired. For both diagnosis and treatment the fluid may have to be drawn off by inserting a needle into the distended pericardial sac; this is called pericardiocentesis.
As the inflammation of the pericardial sac subsides and heals, there may result scar formation of the sac and adhesions between its two layers. This marked scarring around the heart is referred to as constrictive pericarditis. The work of the heart may be greatly impaired, and operative correction may be indicated. This may be by removal of all or part of the outer layer of the pericardium (pericardiectomy) or by releasing the adhesive bands (pericardiolysis).
CONGENITAL DISEASES OF THE HEART
Patent ductus arteriosus is a persistence after birth of an opening between the aorta and the pulmonary artery. This opening (the ductus arteriosus) is necessary to the circulation of the infant before birth. It allows the blood to pass from the right ventricle into the aorta rather than to the nonfunctioning lungs. After birth, this short blood vessel communication normally obliterates so that the blood passes through the pulmonary circulation. In some cases it does not obliterate and the blood takes both this abnormal and the normal routes. The abnormal route allows mixing of the oxygenated and unoxygenated blood; the system is not efficient and the heart pumps under a strain. The length of the abnormal communication may be Vt to 1 inch long. Its diameter varies from pinhead size up to Vi inch. Correction of this condition is by operative ablation of the abnormal artery. This is done through a chest incision by ligating (tying) it or by removing it. This restores the circulation to normal pathways if no other congenital defects exist concurrently.
Coarctation of the aorta is the condition where there is narrowing of the aorta, the body’s major arterial trunk. The aorta comes directly off the top of the heart and then turns on itself to run downward through the trunk of the body. It is at this turn (arch of the aorta) that coarctation usually occurs. The narrowed segment may greatly obstruct the flow of blood, and since this is the body’s main artery the entire body suffers circulatory impairment. The heart itself has to work harder to force the blood through the obstructed area. There is no effective medical treatment for coarctation. Since life expectancy is greatly reduced in this condition, surgery is indicated in anyone whose general condition will permit operation. The procedure entails removal of the obstructed segment of the aorta; the vessel is then reconstructed by re-uniting it, or by the placement of a graft or artificial tube device. When this is the only defect, normal circulation is restored by this operation.
Tetralogy of Fallot is a rather common congenital disease of the heart wherein there are four main defects:
an opening in the septum between the two ventricles,
an abnormal attachment of the aorta to the heart so that it takes part of its origin from the right ventricle (dextroposition of the aorta),
stenosis of the pulmonary valve,
enlargement of the right ventricle.
In this condition there is obstruction to the blood flow through the lungs and the blood does not get normally oxygenated. The circulation of the entire body is affected. This condition is present since birth and demonstrates a typical picture of “blue baby.” Again extensive examination and testing are necessary to confirm the condition. Since there is no medical treatment for this disease complex, and since the outlook in untreated patients is poor, surgical treatment should be offered anyone so afflicted. The operation is usually done in early childhood. The procedure involves three main accomplishments:
connecting a systemic vessel to the pulmonary artery,
connecting the aorta to the pulmonary artery,
relieving the stenosis of the pulmonary valve.
Life has been greatly prolonged in many persons horn with this heart affliction.
Septal defects are openings between the heart chambers which are normally completely separated by a septum. These allow mixing of the oxygenated blood on the left side with the unoxygenated blood on the right side. When the defect is in the septum separating the right and left ventricles it is called interventricular si.ptal defect, and such an abnormal opening in the septum between the auricles is known as interatrial sfptal defect.
Other defects in the walls of the heart which separate it into chambers may occur, such as atrioventricular defects. Complete absence of the ventricular septum does rarely occur, in which case there is essentially a single ventricle.
In the unborn child there is a normal opening between the two auricles. After birth, when the infant begins obtaining oxygen through its own lungs, this shunt is no longer necessary, and it normally seals closed. Should it remain open, the blood intermixes between the two auricles.
Almost all septal defects are amenable to operative correction. Usually this necessitates open cardiotomy, but methods with closed cardiotomy have been used. The opening may be sutured shut when it is small, but large defects may require closure with a tissue graft or an artificial substance. Closure of a septal defect restores the normal circulation if there is no other coexistent congenital heart lesion.
Other congenital defects of the heart and great blood vessels occur with various abnormalities and combinations of abnormalities. The more common specific defects are presented above; other defects which may occur are numerous but less common. Many are amenable to surgical correction or improvement.