Kirklin, John W.

AMONG the many interesting congenital cardiac malformations amenable to surgery today, four will be discussed, namely, coarctation of the aorta, ventricular septal defect, Tetralogy of Fallot, and transposition of the great vessels. Recommendations for surgical therapy are based on the experience at the Mayo Clinic. Coarctation of the aorta continues to be most satisfactorily treated by operation and the hospital mortality risk is extremely low. In general, the optimal age for surgery is about 10 to 12 years. Unusually severe systemic hypertension or cardiac enlargement constitute an indication for somewhat earlier surgery. When infants with isolated coarctation of the aorta show severe cardiac failure, and this certainly occurs although uncommonly, operation should be advised at that age. The risk even then is very low, but few cases may require reoperation at age 12 because of failure of adequate growth of the anastomosis. The indications for repair of ventricular septal defect must take into account the estimated size of the lesion and its hemodynamic effects. Patients with small ventricular septal defects who have normalsized hearts and normal electrocardiograms, that is, those without clinical evidence of significant hemodynamic derangement, are not advised by us to undergo repair of the defect at present. Patients with ventricular septal defect and mild or moderate pulmonary artery hypertension (that is, patients whose pulmonary artery pressure is less than 75% of systemic artery pressure) can be operated upon at essentially no hospital risk. Operation is clearly advisable in all of these patients. Patients with ventricular septal defect who have severe pulmonary artery hypertension associated with a large pulmonary blood flow (and thus with only mild elevation of pulmonary vascular resistance) can be operated upon with a low hospital mortality rate, in the neighborhood of 5%.

Preferential right-to-left shunting of inferior vena caval blood and left-to-right shunting of right-lung blood has been demonstrated to occur in experimental atrial septal defects in dogs as in the congenital defects in human beings. Existence of these preferential shunts proves that uniform mixing of blood does not occur in either atrium.

A total of 696 patients with atrial septal defect (ASD) of either the secundum (90.5%) or the sinus venosus (9.5%) type were operated on at the Mayo Clinic from 1954 through 1965. Pulmonary hypertension (PHT, defined as pulmonary artery systolic pressure of 60 mm Hg or greater) or chronic congestive cardiac failure (CCF) (or both) was associated with 80% of the hospital deaths. For the years 1958 through 1965 (531 cases), the hospital mortality for these three groups was 10% (three of 30), 14% (one of seven), and 18% (two of 11), respectively; only two (0.4%) of the remaining 483 patients died, and both were more than 45 years old (among a total of 93 patients more than 45 years old). There have been no operative deaths among those less than 45 years of age and without PHT or CCF (390 cases) in the years 1958 through 1965. No operative deaths occurred in the years 1963 through 1965. Of 16 patients 60 years or older (1954 through 1965), one has died. A 6- to 12-year follow-up was possible on 397 patients operated on from 1954 through 1960. In the absence of PHT or CCF, 330 survived operation. Among the 53 patients more than 45 years old, four died later (not definitely related to closure of ASD), three were not well, 32 were in excellent health, and 14 were lost to follow-up in 1966. Among the 277 patients less than 45 years old, 10 died later (all but one probably unrelated to closure of ASD), three were unwell, 186 were in excellent health, and 78 were lost to follow-up in 1966. Forty-two patients with PHT survived operation in the period from 1954 through 1960. Ten had pulmonary resistance of more than 640 dynes sec cm -5 ; four of these were well, two had died (with PHT), two had severe PHT, one was in CCF, and one was moderately disabled. Thirty-two had pulmonary resistances of 640 dynes sec cm -5 or less; three of these had died (unrelated to closure of ASD), five were moderately disabled, 16 were in excellent health, and eight were lost to follow-up in 1966. Eighteen patients with CCF survived operation in the period from 1954 through 1960. All had had grade IV disability (New York Heart Association classification). There were three late deaths (one due to severe pulmonary vascular disease and two unrelated to closure of ASD), one patient had grade IV disability, five had grades I to II disability, eight were in excellent health, and one was lost to follow-up in 1966. Paroxysmal arrhythmia occurred in 75 of 397 patients (19%) operated on from 1954 through 1960. In 53 patients it was present preoperatively and persisted postoperatively in 15 of them (28%); in an additional 22 it appeared for the first time after closure of the ASD.

The first 50 cases at the Mayo Clinic of insertion of an aortic valvular homograft after excision of the aortic valve are reported. The hospital mortality rate was 6%. An aortic diastolic murmur was noted in 17% of the surviving patients just prior to their dismissal from the hospital. In none was there evidence of hemodynamically significant aortic valvular incompetence. At follow-up examination 3 to 12 months postoperatively, an aortic diastolic murmur was audible in 44% of the traced patients. Only one patient had hemodynamically significant aortic valvular incompetence. The patients were not given anticoagulant therapy, and there were no thromboembolic complications.

The effect of the mitral Starr-Edwards ball-valve prosthesis on cardiac function was investigated in the dog. Fifteen dogs were studied for the first 48 hours after replacement of the mitral valve (the chordae tendineae [see Figure in the PDF file] had been totally resected, partially resected, or preserved). The cardiac output and left atrial pressure were similar in these three groups of animals and in two animals subjected to sham operation. Ten dogs (five with intact chordae and five with excised chordae) were studied two months after the insertion of a Starr-Edwards prosthesis. In these animals normal hemodynamic values were obtained at rest and during infusion of acetylcholine, except for a marked (liastolic gradient across the prosthesis, which developed at high cardiac output and heart rate. Six dogs were able to complete a standard test of substantial, unrestrained, graded exercise and gave a normal heart rate response. Heart rate increased and was maintained during maximal efforts, to levels of about 300 beats/min, demonstrating that heart rate need not be a limit of cardiac performance. No evidence of left ventricular dysfunction or of a decrement in cardiac performance could be demonstrated in dogs early or late after replacement of the mitral valve with a Starr-Edwards prosthesis. The presence or absence of chordae tendineae was irrelevant to cardiac performance.

1. The results of closure of atrial septal defects in 155 patients over 45 years of age have been reviewed. 2. The over-all operative mortality rate was 6.5%; the operative mortality rate in the last 48 patients was 2.1%. 3. The late results of operation were considered excellent in 83% and good in 13% of the patients. 4. Long-term follow-up studies suggest that patients have significantly longer survival with closure of their defects. 5. It is concluded that operation for atrial septal defect in the older patient may be done at a low risk with an excellent prospect of a good, long-term result in almost all cases.

Cardiac output, stroke volume, and atrial, pulmonary arterial, left ventricular, and systemic arterial pressures were measured preoperatively, during operation, and for 48 hours thereafter in 14 patients undergoing prosthetic replacement of the mitral valve. Cardiac output was usually abnormally low after repair, being lowest 3 to 6 hours after operation. This pattern was different from that in a patient undergoing plication of the posterior leaflet and very different from that in a patient undergoing removal of a left atrial myxoma, who served as controls. Ventricular filling pressure was high, there was no significant diastolic pressure difference across the Starr-Edwards prosthesis, and there was no pressure difference across the left ventricular outflow tract. Blood gas levels and pH were within satisfactory range. The data are interpreted as indicating that impairment of ventricular performance, particularly left, usually contributes significantly to the low cardiac output in these patients. This is probably related in part to preoperative ventricular function. Possible additional contributing factors are discussed.

Seventeen of 44 patients undergoing operation for complete correction of transposition of the great arteries survived operation and were dismissed to return home. Three late deaths followed. Mortality remains high among infants less than one year old and among patients of all ages who have severely elevated pulmonary vascular resistance. Nine of the last 13 patients, in whom repair was accomplished by the Mustard technique, have survived. Late results in all surviving patients have generally been excellent.

Renal performance of seven patients undergoing replacement of the aortic valve was investigated. The initial portion of cardiopulmonary bypass was characterized by low arterial blood pressure and anuria. With a subsequent rise in arterial pressure during bypass, urine flow suddenly increased in five patients. In two patients urine flow did not resume until immediately after cardiopulmonary bypass. The high rate of urine flow at these times is thought to be partially due to a glucose-induced osmotic diuresis. The glomerular filtration rate (inulin clearance) and the effective renal plasma flow (PAH clearance) fell with induction of anesthesia and opening of the chest, but there was no further drop in these functions as a result of total body perfusion. Urine osmolality fell significantly during and immediately after cardiopulmonary bypass. The changes in urine osmolality are thought to be due in part to the osmotic diuresis and in part to a temporary reduction in the renal medullary hyperosmolality secondary to hemodynamic changes. All of the alterations in renal function were reversible in the patients studied.

Sixteen patients with diffuse hypertrophic subaortic stenosis have been treated surgically. Thirteen of 14 patients undergoing excision of hypertrophied muscle from the left ventricular outflow tract via left ventriculotomy or aortotomy have survived. Operation has provided excellent symptomatic relief, associated with eradication or significant reduction of the systolic pressure gradient between the left ventricle and the aorta while the patient is at rest. Operation is recommended for those patients with this disease who are experiencing significant and limiting symptoms related to obstruction of the left ventricular outflow tract.