The technique of modified ultrafiltration is a more efficient application of the concept of ultrafiltration during cardiopulmonary bypass. It has been shown to be superior to the conventional method of ultrafiltration.

The method can save considerable quantities of donor blood by returning not only the red cells, but also the white cells, platelets, and clotting factors back to the patient, components which otherwise would be discarded. The elevation of the hematocrit made possible by this method after bypass will permit an “acceptable” hematocrit to be achieved when temperatures become normal after ultrafiltration. The return of platelets and clotting factors along with a high hematocrit will contribute towards significantly minimizing the postoperative loss of blood, and, consequently, the amount of blood requiring to be transfused. The possibility of elevation of the hematocrit allows for a lower hematocrit during bypass. This can achieve a considerable saving of donor blood, particularly in small children who invariably need blood added to the prime, making bloodless pediatric surgery a real possibility. The technique also minimizes the rise in total water in the body after cardiopulmonary bypass in children and promises favorably to alter the course of leaking capillaries as seen frequently in neonates and infants. It has been shown to improve hemodynamics at a crucial time when the patient has been weaned from cardiopulmonary bypass and needs optimum conditions for recovery. From the point of view of research, ultrafiltration offers a window to look at the inflammatory process induced by cardiopulmonary bypass.

It promises to be a valuable technique to investigate the elimination and possibly quantification of toxic metabolites produced during bypass. It also allows evaluation and assessment of different protocols for bypass, involving varying rates of flow and temperature, for their response to the production of these toxic metabolites, thus offering the potential to achieve a model of cardiopulmonary bypass which is as physiological as possible. With advances in the systems of perfusion, aided by computers, it should be possible to control the rate of ultrafiltration and precisely regulate the transfusion of the venous reservoir fluid with the aid of feedback loops from the venous and arterial pressures in the heart. This could make ultrafiltration an integral part of routine cardiopulmonary bypass.

There is a clear and present danger for the patient considered for Fontan's operation in the presence of excessive ventricular hypertrophy and/or mass. Such ventricular hypertrophy and/or mass probably reflects singly, or in combination, banding of the pulmonary trunk and subaortic stenosis, as well as other factors. While one can construct a number of therapeutic algorithms for patients seen at various ages with a restrictive ventricular septal defect and subaortic stenosis in the setting of double inlet left ventricle and discordant ventriculoarterial connections, the optimal management should be to minimize the potential risks for development of subaortic stenosis and excessive ventricular hypertrophy and/or mass.

Transesophageal echocardiography has gained an established role in the evaluation and management of the adult patient with acquired cardiac disease. Unlike the transthoracic approach, the transesophageal approach provides excellent imaging of posterior cardiac structures in virtually all patients.

Follow-up cardiac catheterization and angiography was performed in 23 patients after complete, staged repair of pulmonary atresia with ventricular septal defect and multiple systemic-to-pulmonary collateral arteries. Time interval from repair varied from 0.2 to 89 months (mean 26 months). Major residual anomalies of arborization of the pulmonary arteries, with or without pulmonary vascular disease, were present in six patients, two of whom had die patch on the ventricular septal defect perforated because of systemic or suprasystemic right ventricular pressure in the early postoperative period after repair. Both of these children later died, while the other four patients were found to have moderately to severely elevated ventricular pressure ratios and pulmonary arterial pressure measurements, though they are all alive at follow-up intervals from 20 months to 6.8 years. The remaining 17 patients all had hemodynamically satisfactory or good results, with pulmonary arterial mean pressures ranging from 8 to 30 mm Hg (mean 22 mm Hg) and pressure ratios between the ventricles from 0.24 to 0.75 (mean 0.43)—the higher ratios generally reflecting gradients across the conduit valve. Angiography demonstrated that the hypoplastic pulmonary arteries increased in size to normal dimensions, during staging, in most patients, though abnormalities of arborization persisted in several. Analysis of the data from the entire cohort of 58 patients, who were accepted for staging towards repair, showed a significant association between early age at entry to the program and likelihood of complete repair being achievable.

Cardiopulmonary bypass in neonates is markedly different from the procedure used in children above 10 kg and in adults. There are two major reasons for this—first, the mismatch between the volume of the heart-lung machine circuit and that of the blood in the patient and second, the immaturity of tissues in the first three months of life.

Lung biopsies were taken from 30 children aged three months to 15 years (median, 11 months) who had pulmonary hypertensive congenital heart disease and were living at an altitude of 1750 meters. They had either a ventricular septal defect and/or patency of the arterial duct, atrioventricular septal defect or complete transposition with a ventricular septal defect. Biopsies were studied using quantitative morphometric light microscopic techniques. All patients with a ventricular septal defect with or without patency of the arterial duct showed a significant increase in mean percentage arterial medial thickness of both pre- and intraacinar pulmonary arteries compared with those of normal children of similar age living at sea level (p<0.001 for both pre- and intraacinar vessels) and with children with a ventricular septal defect living at sea level (p<0.001 for both pre- and intraacinar vessels). Extension of muscle to more peripheral pulmonary arteries was also greater. Intimal proliferation and fibrosis was seen in 10 patients, in three of whom it was severe. Intimal proliferation occurred more frequently than in children with a ventricular septal defect living at sea level. The findings were similar in patients with atrioventricular septal defect and complete transposition with ventricular septal defect. These findings suggest that patients with congenital heart disease who live at a relatively high altitude develop pulmonary vascular disease more rapidly than do those living at sea level.

We studied 28 fetal rats with atrioventricular septal defect with a common orifice produced from 300 fetuses treated with bis-diamine (200mg) on the ninth and tenth day of pregnancy. After undergoing rapid whole- body freezing on the 21st day, they were studied by means of serial cross-sectional photographs of the frozen thorax. Forty-one fetuses with normal hearts subsequent to treatment with bis-diamine served as controls. Atrioventricular septal defect was isolated in three, or was associated with either tetralogy of Fallot (n=14) or common arterial trunk (n=11). Fetal hydrops was associated with evidence of regurgitation of the atrioventricular valves. In a subgroup with larger right atrial volumes (increased by more than two standard deviation over the mean in the controls), the following parameters were significantly increased: subcutaneous edema, pericardial effusion, thickening of the left atrioventricular valve, cardiac chamber volumes and masses. The superior and inferior caval veins, and the descending aorta were significantly smaller in fetuses with atrioventricular septal defect than in controls. Fetal atrioventricular septal defect, therefore, was associated frequently with hydrops and increased volumes of the right atrium and both ventricles. Hydropic changes included cutaneous edema and increased pericardial, pleural, and peritoneal fluid.

The advent of cardiopulmonary bypass in 1953, and its subsequent continuous refinements, have securely established the specialty of cardiovascular surgery. In conjunction with the improved methods of myocardial preservation, this has allowed the safe repair of acquired and complex congenital cardiac defects. During the years, the many variables of the systems used for cardiopulmonary bypass have been altered to the point that most operations are now reproducible with, relatively, low morbidity and mortality. Although in its present form the system is quite reasonable for most routine surgery, it is far from perfect. There remains, therefore, a quest for alterations to improve the system as an ongoing process. Certain complications of open-heart surgery persist and many new and unique approaches to the concept of organ protection and the treatment of these complications must be developed and refined.

One of the most challenging applications of cardiopulmonary bypass is corrective cardiac surgery in the neonate. The small size and high metabolic demand of these patients require miniaturized but efficient equipment. Even with the most advanced components, the volume required to prime the perfusion circuit is typically more than twice the blood volume of a neonate. Neonates have limited cardiac and pulmonary reserves and, therefore, great care is required to preserve those organs that have often already been subjected to hypoxemia, congestive heart failure, or low cardiac output prior to surgery. There is a tendency toward extravascular movement of fluids in newborns subjected to bypass that can adversely affect outcome. Careful monitoring and precise management of perfusion are essential to a successful procedure and optimal recovery of these patients.

We have studied 140 patients undergoing corrective surgery for aortic coarctation between 1952 and 1972, following them for a mean period of 23 years. Of the patients, 19 underwent surgery in infancy (age range 15 days to 190 days, mean 84 days), 52 during childhood, with a mean age of 11.8 years (range 1 years), and 69 as adults (age range 18−50 years, mean 30.5 years). All infants were symptomatic at presentation and fared poorly because of associated cardiac lesions. Their operative mortality was 11%, and mortality prior to discharge from hospital was 21%. Of the survivors, 38% required surgery for recurrent coarctation. There were three late deaths. Of the survivors, 90% were asymptomatic at long-term follow-up. Only six children (11%) were symptomatic at presentation. There was no operative or early postoperative mortality, and only three late deaths (6%). Of the 49 survivors, 96% were asymptomatic, and only six required antihypertensive medication. The recoarctation rate was 9% (four patients). In the group undergoing surgery as adults, 42% were symptomatic at presentation with 90% being hypertensive. There were two postoperative deaths and a late mortality of 22%, which was mainly related to the cardiovascular complications. None of the adults had suffered recoarctation, but 48% remained hypertensive. Our study confirms that the prognosis of patients with aortic coarctation presenting in infancy is related to presence of associated cardiac anomalies and operative complications. The prognosis in older patients, and particularly adults, is related to residual hypertension and resultant cardiovascular disease. Surgical correction reduces symptoms and improves life expectancy, regardless of the age at operation, with the best overall prognosis being obtained for those undergoing surgery as children.

The diameter of the pulmonary outflow tract was measured from the right ventricular cineangiogram at different phases of the cardiac cycle prior to balloon valvoplasty in 54 patients with congenital pulmonary valvar stenosis. Measured at the level of the hinge point of the valvar leaflets, the pulmonary outflow tract was found to be largest at end-diastole and smallest at end-systole. The mean increase in diameter from systole to diastole was 25.3% (range 6–53%) for 47 patients with typical valvar stenosis, and 24.3% (range 14–41%) for seven patients with dysplastic valvar leaflets (p>0.5). Dilatation using balloons less than 1.2 times the size of the maximal end-diastolic diameter produced a mean reduction in the pressure gradient from right ventricle to pulmonary trunk of 71.1%, compared to 76.2% with bigger balloons (p>0.3). Two patients with an initial ratio between balloon and outflow tract of 0.9 required a second dilatation. The timing of measurement of the diameter of the pulmonary outflow tract should be standardized. Oversized balloons probably are not necessary for pulmonary valvoplasty.