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A total of 550 intracardiac operations were performed with the aid of profound hypothermia and circulatory arrest between March, 1971, and December, 1979. Both cooling and rewarming were effected by means of an extracorporeal heat exchanger. Overall mortality was 20%, falling to 10% in 1979. Highest risks were associated with operations in the neonatal period and for unusually complex defects. The technique has proved safe for straightforward corrections in young age groups and is especially valuable for selected complex lesions in older children and those requiring reoperation. Although circulatory arrest has greatly extended the range of corrective heart operation in infancy, we believe there is still a significant place for palliative procedures in appropriate circumstances. Neurologic complications attributed to the technique have been uncommon, and only 4.5% of the survivors have any recognizable residual neurologic lesion, whether coincidental or resulting from circulatory arrest. The technique is simple, reliable, and generally safe.

Experimentally induced hypothermia (20 degrees C) for 60 minutes in dogs provokes a significant decrease in the platelet count, which reverses during subsequent rewarming, and the constant release of a heparin-like factor, which reacts as a specific inhibitor of factor Xa. This phenomenon is also rapidly reversible, and heparin values are not significantly different from control levels after 90 minutes of rewarming. The mean maximal concentration of heparin-like material is 0.54 U/ml, or about double control levels. Its half-life is approximately 90 minutes. The level of circulating antithrombin III was not modified during hypothermia and rewarming.

Infants with ventricular septal defect (VSD) who are symptomatic despite intensive medical therapy require surgical intervention. Choice of treatment depends upon the cumulative mortality and morbidity rates of the two-stage approach of initial pulmonary artery banding followed by debanding and VSD closure as compared to the risk of primary intracardiac repair in infancy. Sixteen infants underwent pulmonary artery banding at Columbia-Presbyterian Medical Center between 1967 and 1976, with one operative death but with a significant incidence of morbidity and late death. Forty patients underwent pulmonary artery debanding and closure of VSD with three operative deaths. This second-stage procedure was frequently complicated by repair of acquired lesions. During the same 10 year period 37 infants underwent primary closure of VSD with eight operative deaths. The morbidity related to this procedure is low. With the use of profound hypothermia and circulatory arrest, results have significantly improved and the risk of early correction now compares favorably with the cumulative mortality rate of the two-stage approach. Primary intracardiac repair is the procedure of choice.

An initial series of 180 patients subjected to definitive repair of cardiac malformations during infancy is presented. The operations were performed with profound hypothermia and circulatory stasis. Statistics relating to the entire series of patients are presented and discussed, after which the results among eleven individual groups of patients categorized by type of cardiovascular lesion are analyzed. There were 113 survivors, representing an over-all mortality rate of 37 per cent. The mortality rate was highest among patients severely ill preoperatively and among those with complex malformations. Deaths were also more frequent among infants under 6 months of age and less than 5 kilograms in weight. Analysis shows a steady increase in percentage of patient survival over the years reported from December, 1967, to April, 1975.

Primary aortic arch reconstruction was undertaken in three neonates with interrupted aortic arch and ventricular septal defect Total ascending aortic occlusion without cardiopulmonary bypass or profound hypothermia permitted, in each case, a rapid tension-free end-to-side descending-to-ascending aortic anastomosis without resulting neurologic or cardiac sequelae. This technique offers distinct advantages over previously described methods and should be considered whenever interrupted aortic arch is present with a ventricular septal defect.

The late hemodynamic and radiologic findings were good or excellent in 96 percent of 23 infants in whom tetralogy of Fallot was repaired with the use of profound hypothermia. These results encourage continuation of the policy of early repair rather than palliation in tetralogy of Fallot. The preoperative cineangiocardiographic assessment of the type and severity of the pulmonary stenosis accurately predicted the findings at operation and the type of repair required. In infants between 1 and 21 months of age and 3 and 10 kilograms in weight, a main pulmonary artery (MPA) diameter of less than 7 mm. was the cineangiocardiographic measurement most accurately predicting the necessity for an outflow patch across the pulmonary ring. Postoperative studies showed significant increases in the MPA and pulmonary ring diameters. A method of cineangiocardiographic assessment of pulmonary incompetence is presented. Severe mechanical pulmonary incompetence in some patients produced mild hemodynamic effects by radiologic criteria.

A bilateral thoracotomy with cardiopulmonary bypass and profound hypothermia has become our preferred method of procurement of organs for combined heart-lung transplantation and has replaced the sternotomy without cardiopulmonary bypass as initially used. This technique has provided good exposure and has facilitated dissection and hemostasis of the posterior aspect of the middle mediastinum.

Cold injury has been suggested as a potential limitation to the use of temperatures below 10° to 15° C in clinical myocardial preservation. The isolated effects of profound hypothermia on myocardial function and energy metabolism were studied in the working rat heart preparation. Each heart was isolated and stabilized; then initial aortic flow, coronary flow, and heart rate were measured. The heart then was perfused in the Langendorf mode with oxygenated Krebs-Henseleit buffer for 20 minutes at 0.5°, 4°, 10°, 15°, or 20° C. After being rewarmed to 37° C, the heart was returned to the working mode for final functional measurements. In a control group, the perfusion temperature was kept at 37° C. Recovery of function in hearts exposed to hypothermic perfusion was not significantly different from that observed in the hearts kept at 37° C. When cold exposure time to 0.5° C perfusion was extended to 2 hours, heart function still returned to the same level as that of control hearts maintained at 37° C, and adenosine triphosphate (ATP) and glycogen levels were higher than those in the control group. Thus, under these conditions, cold exposure per se, even for 2 hours at temperatures near 0° C, has no deleterious effect upon myocardial function and energy metabolism.

We have previously demonstrated the technical feasibility of an en bloc double lung transplantation in acute canine experiments. We have now conducted survival experiments in cynomolgus monkeys. Profound hypothermia and circulatory arrest were used to avoid the need for cardiopulmonary bypass in these very small animals. Because of the complexities of this technique, few long-term survivals resulted, but these experiments did confirm excellent lung function and satisfactory tracheal healing. On the basis of these experiments, we have performed our first clinical double lung transplantation on a 42-year-old woman with end-stage emphysema caused by α2-antitrypsin deficiency. The patient has returned to normal activities with excellent lung function.

Dissection for closure of a Blalock-Taussig shunt can occasionally be difficult or hazardous at the time of corrective operation. The technique traditionally used for closure of a Potts anastomosis, in which profound hypothermia and circulatory arrest are used, has been applied successfully in 11 operations for control of 12 Blalock-Taussig anastomoses. The technique is described.

Since 1970, 7 patients varying in age between 1 month and 3 years have had successful correction of an aortopulmonary septal defect. Three of these patients had associated cardiac lesions which were repaired at the same time. Extracorporeal circulation was used in 3 patients and profound hypothermia with limited extracorporeal circulation in 4. In 5 patients the defect was closed with a Dacron patch through a transaortic approach. The advantages of this method are discussed.

Summary Development of an improved method for instantaneous freezing (-196° C.) of sequential cerebral biopsies permits the accurate determination of ATP (adenosine triphosphate) disappearance during complete circulatory arrest and recovery. Control cerebral ATP concentrations in biopsies from 30 normothermic dogs equalled 2.42 ± 0.16 micromoles per gram (S.D.). Simultaneous aortic and vena caval occlusion, for periods of 4, 6, or 8 minutes, resulted in a 50 per cent decrease of cerebral ATP within 3.8 minutes. Electroen-cephalographic silence occurred at 20.9 ± 3.1 seconds, coincident with the loss of less than 10 per cent of control ATP content. Reappearance of brain ATP after resumption of flow correlated inversely with the duration of circulatory arrest. Eleven dogs were cooled to 5° to 11° C. (esophageal) with the use of high-flow extracorporeal perfusion for 50 minutes with attendant reduction of cerebral ATP to 88.6 ± 7.4 per cent of normothermic control levels. EEG silence occurred at 16.8° ± 3.5° C. (esophageal), coincident with the loss of less than 10 per cent of control ATP concentrations. Circulatory arrest resulted in a 50 per cent reduction in cerebral ATP after 13.3 minutes. Recovery of ATP with rewarming was observed after 30 and 60, but not 90, minutes of hypothermic arrest. EEG recovery was associated with return of ATP concentrations to 89 per cent of normothermic control levels. Profound hypothermia results in a three- to fourfold increase in survival of cerebral ATP during circulatory arrest. We wish to thank Robert Gelein and Marvin Nunn for valuable technical assistance.