Heart surgery encompasses the operations performed on the heart and its neighboring vessels to correct or alleviate heart
disease. Performing surgery on the heart requires that the heart and lungs be emptied of blood and immobilized, so that the structures on and within the heart can be seen clearly and repaired. During heart surgery, blood flow is diverted from the patient's own heart and lungs to a heart-lung machine which performs the functions of the patient's heart and lungs for the period of time required to perform the operation. This technique is termed cardiopulmonary bypass. During most heart operations the blood and body are cooled to slow the metabolism of the body's organs and reduce their demand for oxygen, thereby minimizing organ injury. The infusion of a potassium-containing solution directly into the coronary arteries prevents the heart from beating during the operation.
For very complex operations, particularly in infants, it is sometimes necessary to stop not only the heart but all blood flow to the rest of the body. The patient is cooled to very low temperatures, and blood flow from the heart-lung machine is stopped. During this time, the critical portions of the heart operation are performed. Once these portions of the procedure have been completed, blood flow to the rest of the body is resumed and the patient is rewarmed, after which the heart is allowed to beat spontaneously again. Once the function of the heart is determined to be satisfactory by the surgeon, the heart gradually resumes its workload.
In children, heart disease typically results from congenital heart defects, anomalies present at the time of birth. Typical problems include defects in the tissue separating the ventricles or atria, holes between the aorta and the pulmonary artery, narrowing of the aorta and transposition of the ventricles, aorta, and pulmonary artery. Many patients may have combinations of the above defects or other rarer lesions, making surgical repair quite complex. The trend in heart surgery to repair congenital defects has been toward as complete an anatomic repair as early as possible in children showing symptoms.
In adults, heart surgery usually occurs as a result of acquired disease involving the coronary arteries or the heart valves. Most commonly, disease of the coronary arteries is due to narrowing or stenosis of the coronary arteries due to atherosclerosis. In many circumstances, these narrowings or obstructions allow bypass around the site of blockage to a part of the vessel that is less diseased. A combination of the patient's own arteries and veins can be used to perform this operation, a procedure known as coronary artery bypass grafting.
The heart valves are most commonly affected by diseases that prevent proper emptying of the heart chambers or allow blood to flow back into emptied chambers. When these diseases become severe, replacement of the heart valves is necessary. During surgery, the diseased valve is removed and replaced with an artificial heart valve. Replacement valves can be mechanical or from pigs.
Some patients have sustained such severe damage to their hearts that surgical correction is not possible. Cardiac transplantation is an option for such patients. The patient's heart is removed and replaced with an undiseased heart from an individual who has suffered brain death but whose heart remains viable. At the present time, approximately 90 percent of cardiac transplant recipients will survive one year and 70 percent will live for five years following the operation.