Is it necessary to routinely fenestrate an extracardiac fontan?

OBJECTIVES: This study was conducted to assess the need for, and use of, fenestration of an extracardiac conduit Fontan. BACKGROUND: Fenestration of a Fontan connection has been proposed as a means of improving outcomes of single ventricle palliation. The benefit of fenestration is likely to be greatest in the early postoperative period when patients may experience increased pulmonary vascular resistance and decreased ventricular function due to the effects of cardiopulmonary bypass, aortic cross-clamping and positive pressure ventilation. However, there are potential drawbacks to fenestration. The utility of fenestration with extracardiac Fontan operation has not been determined. METHODS: Since 1992, 81 patients have undergone a modification of the Fontan procedure in which an extracardiac inferior cavopulmonary conduit is used in combination with a previously staged bidirectional Glenn anastomosis. We conducted a retrospective review of these patients. RESULTS: Fenestration was performed selectively in 32 patients (39%), including only 2 of the last 38 (5%). In seven patients, a fenestration was placed or clipped in the early postoperative period without cardiopulmonary bypass. There were two operative deaths. Prolonged (>2 weeks) pleural drainage occurred in 13 patients, 8 with fenestration and 5 without. In addition to undergoing earlier Fontan in our experience, patients who had a fenestration placed had significantly higher preoperative pulmonary vascular resistance, significantly higher common atrial pressure after Fontan and significantly lower post-Fontan systemic arterial oxygen saturation. Fontan pressure did not differ between nonfenestrated and fenestrated patients. At follow-up ranging to five years, there were two late deaths and no patients developed protein losing enteropathy. CONCLUSIONS: Fenestration is not necessary in most Fontan patients when an extracardiac conduit technique is performed as described in this article, and therefore, should not be performed routinely with the extracardiac conduit Fontan. The need for fenestration should be assessed after cardiopulmonary bypass when hemodynamics can be evaluated accurately. Fenestration can be placed and revised easily without bypass and with minimal intervention in patients with an extracardiac conduit Fontan.

One-stage complete unifocalization in infants: when should the ventricular septal defect be closed?

BACKGROUND: The decision whether to close the ventricular septal defect at the time of unifocalization in patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collaterals may be difficult. The purpose of this study was to develop morphologic and physiologic methods to aid in deciding whether to close the ventricular septal defect in patients undergoing one-stage unifocalization. METHODS: Between July 1992 and April 1996, 27 infants with pulmonary atresia, ventricular septal defect, and aortopulmonary collaterals were treated at our institution. Midline complete unifocalization was performed in 25 patients-the ventricular septal defect was closed in 17 and left open in eight. Two patients with severe distal collateral stenoses underwent staged unifocalization. Pulmonary artery and collateral sizes were measured from preoperative angiograms and used to calculate the indexed cross-sectional area of the total neopulmonary artery bed. An intraoperative pulmonary flow study previously validated with experiments in neonatal lambs was performed in six patients: the unifocalized neopulmonary arteries were perfused with a known flow and pulmonary artery pressures were recorded. RESULTS: The neopulmonary artery index was greater in patients who underwent ventricular septal defect closure than in those who did not (p = 0.001), although the values did overlap. This index correlated with the postoperative right ventricular/left ventricular pressure ratio (p = 0.037). Mean pulmonary artery pressures obtained during the intraoperative flow study and after bypass were comparable. CONCLUSION: The total neopulmonary artery index correlates with postrepair right ventricular/left ventricular pressure ratio and is useful in deciding when to close the ventricular septal defect if it is larger than 200 mm2/m2. The pulmonary flow study is helpful in deciding whether to close the ventricular septal defect in all patients.

Pulmonary artery growth after bidirectional cavopulmonary shunt: is there a cause for concern?

OBJECTIVE: Our objective was to analyze changes in pulmonary artery size after bidirectional cavopulmonary shunt. METHODS: All 47 patients who underwent bidirectional cavopulmonary shunt between March 1990 and May 1995 who had preoperative and postoperative angiograms available for review were selected for study. This included 24 patients who had also undergone a modified Fontan operation. Clinical records were reviewed retrospectively and cross-sectional follow-up was obtained by direct physician contact. Angiograms were reveiwed, and the right and left pulmonary artery diameters were each measured at two locations: immediately distal to their origin and at the narrowest point. In addition, the lower lobe pulmonary artery branch was measured just distal to its origin. Cross-sectional areas (left, right, and total) at each point of measurement were indexed to body surface area. Angiographic and hemodynamic data were analyzed. RESULTS: Changes in the various measures of pulmonary artery size after bidirectional cavopulmonary shunt varied considerably. On average the absolute diameters increased for all measures, but the increase in diameter was significant only for the lower lobe arteries. All pulmonary artery indices decreased on average, but these changes did not approach significance. Patients who underwent pulmonary artery augmentation at the time of bidirectional cavopulmonary shunt had significantly smaller pulmonary artery indices before pulmonary artery augmentation, relative to those who did not undergo pulmonary artery repair, and significantly greater changes (possibly to a large extent owing to pulmonary artery repair) in the right and left pulmonary artery index after bidirectional cavopulmonary shunt. Lower lobe indices did not differ preoperatively or exhibit different degrees of change in size between patients who did and did not undergo pulmonary artery repair. One patient died after Fontan completion (pulmonary artery index: 305 mm2/m2), and none of the factors analyzed correlated with Fontan outcomes. CONCLUSIONS: A more appropriate measure of pulmonary artery growth is the indexed cross-sectional area of the lower lobe branch of the right and left pulmonary arteries, which is less likely to be altered surgically with systemic-pulmonary shunts, pulmonary artery repair, and the bidirectional cavopulmonary anastomosis itself. Pulmonary artery indices, including the lower lobe index, do not change significantly after bidirectional cavopulmonary shunt during medium-term follow-up and do not influence the Fontan outcome.

Early results of the extracardiac conduit Fontan operation.

BACKGROUND: Among the modifications of the Fontan operation, the extracardiac approach may offer the greatest potential for optimizing early postoperative ventricular and pulmonary vascular function, insofar as it can be performed with short periods of normothermic partial cardiopulmonary bypass and without cardioplegic arrest in most cases. In this study, we reviewed our experience with the extracardiac conduit Fontan operation, with a focus on early postoperative outcomes. METHODS AND RESULTS: Between July 1992 and April 1997, 51 patients (median age 4.9 years) underwent an extracardiac conduit Fontan operation. Median cardiopulmonary bypass time was 92 minutes and has decreased significantly over the course of our experience. Intracardiac procedures were performed in only 5 patients (10%), and the aorta was crossclamped in only 11 (22%). Intraoperative fenestration was performed in 24 patients (47%). There were no early deaths. Fontan failure occurred in 1 patient who was a poor candidate for the Fontan procedure. Transient supraventricular tachyarrhythmias occurred in 5 patients (10%). Median duration of chest tube drainage was 8 days. Factors significantly associated with prolonged resource use (mechanical ventilation, inotropic support, intensive care unit stay, and hospital stay) included longer bypass time and higher Fontan pressure. At a median follow-up of 1.9 years, there was 1 death from bleeding at reoperation. CONCLUSIONS: The extracardiac conduit Fontan procedure can be performed with minimal mortality and morbidity. Improved results may be related to advantages of the extracardiac approach and improved preservation of ventricular and pulmonary vascular function.

Hemidiaphragmatic paralysis increases postoperative morbidity after a modified Fontan operation.

OBJECTIVES: After a Fontan procedure, forward pulmonary blood flow is augmented during inspiration because of negative intrathoracic pressure. Total pulmonary blood flow is higher during inspiration. With hemidiaphragmatic paralysis, inspiratory augmentation of pulmonary flow is lost or diminished. The objective of this study was to compare early postoperative morbidity after the modified Fontan operation in patients with and without hemidiaphragmatic paralysis. METHODS: A case-control analysis was performed comparing 10 patients with documented hemidiaphragmatic paralysis against 30 patients without paralysis who were matched for diagnosis, fenestration, and age. The following early postoperative outcomes were assessed: duration of ventilator support, duration of hospital stay, incidence of ascites, prolonged effusions, and readmission. RESULTS: Preoperatively, there were no significant differences between the 2 groups. However, among the postoperative outcomes, the duration of hospital stay (25.4 +/- 16.6 days vs 10.8 +/- 6.3 days; P =.03), incidence of ascites (70% vs 3%; P <.001), prolonged pleural effusions (60% vs 13%; P =.007), and readmission (50% vs 7%; P =.007) were significantly greater in patients with hemidiaphragmatic paralysis than in those without hemidiaphragmatic paralysis. CONCLUSIONS: Hemidiaphragmatic paralysis after the modified Fontan operation is associated with an increase in early morbidity. Care should be taken to avoid injury to the phrenic nerve. Patients with prolonged effusions should be evaluated for hemidiaphragmatic paralysis.

Endothelin receptor blockade prevents the rise in pulmonary vascular resistance after cardiopulmonary bypass in lambs with increased pulmonary blood flow.

BACKGROUND: Children with increased pulmonary blood flow may experience morbidity as the result of increased pulmonary vascular resistance after operations in which cardiopulmonary bypass is used. Plasma levels of endothelin-1, a potent vasoactive substance implicated in pulmonary hypertension, are increased after cardiopulmonary bypass. OBJECTIVES: In a lamb model of increased pulmonary blood flow after in utero placement of an aortopulmonary shunt, we characterized the changes in pulmonary vascular resistance induced by hypothermic cardiopulmonary bypass and investigated the role of endothelin-1 and endothelin-A receptor activation in postbypass pulmonary hypertension. METHODS: In eleven 1-month-old lambs, the shunt was closed, and vascular pressures and blood flows were monitored. An infusion of a selective endothelin-A receptor blocker (PD 156707; 1.0 mg/kg/h) or drug vehicle (saline solution) was then begun 30 minutes before cardiopulmonary bypass and continued for 4 hours after bypass. The hemodynamic variables were monitored, and plasma endothelin-1 concentrations were determined before, during, and for 6 hours after cardiopulmonary bypass. RESULTS: After 90 minutes of hypothermic cardiopulmonary bypass, both pulmonary arterial pressure and pulmonary vascular resistance increased significantly in saline-treated lambs during the 6-hour study period (P <.05). In lambs pretreated with PD 156707, pulmonary arterial pressure and pulmonary vascular resistance decreased (P <. 05). After bypass, plasma endothelin-1 concentrations increased in all lambs; there was a positive correlation between postbypass pulmonary vascular resistance and plasma endothelin-1 concentrations (P <.05). CONCLUSIONS: This study suggests that endothelin-A receptor-induced pulmonary vasoconstriction mediates, in part, the rise in pulmonary vascular resistance after cardiopulmonary bypass. Endothelin-A receptor antagonists may decrease morbidity in children at risk for postbypass pulmonary hypertension. This potential therapy warrants further investigation.

A prospective randomized study comparing volume-standardized modified and conventional ultrafiltration in pediatric cardiac surgery.

BACKGROUND: Modified ultrafiltration has been touted as superior to conventional ultrafiltration for attenuating the consequences of hemodilution after cardiac surgery with cardiopulmonary bypass in children. We conducted a prospective randomized study to test the hypothesis that modified and conventional ultrafiltration have similar clinical effects when a standardized volume of fluid is removed. METHODS: From October 1998 to September 1999, 110 children weighing 15 kg or less (median weight 6.1 kg, median age 6.3 months) undergoing surgery with cardiopulmonary bypass for functionally biventricular congenital heart disease were randomized to conventional (n = 67) or arteriovenous modified ultrafiltration (n = 43) for hemoconcentration. The volume of fluid removed with both methods was standardized as a percentage of effective fluid balance (the sum of prime volume and volume added during cardiopulmonary bypass minus urine output): in patients weighing less than 10 kg, 50% of effective fluid balance was removed, whereas 60% was removed in patients weighing 10 to 15 kg. Hematocrit, hemodynamics, ventricular function, transfusion of blood products, and postoperative resource use were compared between groups. RESULTS: There were no significant differences between groups in age, weight, or duration of cardiopulmonary bypass. The total volume of fluid added in the prime and during bypass was greater in patients undergoing conventional ultrafiltration than in those receiving modified ultrafiltration (205 +/- 123 vs 162 +/- 74 mL/kg; P =.05), although the difference was due primarily to a greater indexed priming volume in patients having conventional ultrafiltration. There was no difference in the percentage of effective fluid balance that was removed in the 2 groups. Accordingly, the volume of ultrafiltrate was greater in patients receiving conventional than modified ultrafiltration (95 +/- 63 vs 68 +/- 28 mL/kg; P =.01). Preoperative and postoperative hematocrit levels were 35.6% +/- 6.6% and 36.3% +/- 5.6% in patients having conventional ultrafiltration and 34.4% +/- 6.7% and 38.7% +/- 7.5% in those having modified ultrafiltration. By repeated-measures analysis of variance, patients receiving modified and conventional ultrafiltration did not differ with respect to hematocrit value (P =.87), mean arterial pressure (P =.85), heart rate (P =.43), or left ventricular shortening fraction (P =.21) from baseline to the postbypass measurements. There were no differences between groups in duration of mechanical ventilation, stay in the intensive care unit, or hospitalization. CONCLUSIONS: When a standardized volume of fluid is removed, hematocrit, hemodynamics, ventricular function, requirement for blood products, and postoperative resource use do not differ between pediatric patients receiving conventional and modified ultrafiltration for hemoconcentration after cardiac surgery.

Revision of previous Fontan connections to total extracardiac cavopulmonary anastomosis: A multicenter experience.

BACKGROUND: Conversion to total extracardiac cavopulmonary anastomosis is an option for managing patients with dysfunction of a prior Fontan connection. METHODS: Thirty-one patients (19.9 +/- 8.8 years) underwent revision of a previous Fontan connection to total extracardiac cavopulmonary anastomosis at four institutions. Complications of the previous Fontan connection included atrial tachyarrhythmias (n = 20), progressive heart failure (n = 17), Fontan pathway obstruction (n = 10), effusions (n = 10), pulmonary venous obstruction by an enlarged right atrium (n = 6), protein-losing enteropathy (n = 3), right atrial thrombus (n = 2), subaortic stenosis (n = 1), atrioventricular valve regurgitation (n = 3), and Fontan baffle leak (n = 5). Conversion to an extracardiac cavopulmonary connection was performed with a nonvalved conduit from the inferior vena cava to the right pulmonary artery, with additional procedures as necessary. RESULTS: There have been 3 deaths. Two patients died in the perioperative period of heart failure and massive effusions. The third patient died suddenly 8 months after the operation. All surviving patients were in New York Heart Association class I (n = 20) or II (n = 7), except for 1 patient who underwent heart transplantation. Early postoperative arrhythmias occurred in 10 patients: 4 required pacemakers, and medical therapy was sufficient in 6. In 15 patients, pre-revision arrhythmias were improved. Effusions resolved in all but 1 of the patients in whom they were present before revision. The condition of 2 patients with protein-losing enteropathy improved within 30 days. CONCLUSIONS: Conversion of a failing Fontan connection to extracardiac cavopulmonary connection can be achieved with low morbidity and mortality. Optimally, revision should be undertaken early in symptomatic patients before irreversible ventricular failure ensues.

Intestinal perforation from gastrointestinal histoplasmosis in acquired immunodeficiency syndrome. Case report and review of the literature.

Gastrointestinal involvement with histoplasmosis in patients with the acquired immunodeficiency syndrome is a rare but documented phenomenon. Most patients present with diarrhea, fever, and abdominal pain. We present a case of a woman who tested positive for the human immunodeficiency virus antibody who developed an intestinal perforation due to Histoplasma capsulatum of the ileum. The patient, whose only risk factor was a blood transfusion 8 years earlier, had been previously diagnosed as having disseminated histoplasmosis with gastrointestinal involvement. While receiving oral antifungal treatment (itraconazole), she developed two separate areas of ileal perforation due to H capsulatum. Complications from gastrointestinal involvement with histoplasmosis, such as perforation, should be considered in patients infected with the human immunodeficiency virus with signs and symptoms suggesting abdominal disease.

Extracardiac conduit Fontan procedure without cardiopulmonary bypass.

There are a number of potential advantages of extracardiac conduit cavopulmonary anastomosis for palliation of functional single ventricle heart disease, including the ability to perform the operation with no aortic cross-clamping and with minimal duration of extracorporeal circulation. In many patients, it may be possible to perform the procedure without cardiopulmonary bypass altogether. In this report, we present our technique for performing the extracardiac conduit Fontan operation without cardiopulmonary bypass.

Neutrophil degranulation and complement activation during fetal cardiac bypass.

BACKGROUND: Fetal cardiac bypass results in dysfunction of the fetoplacental unit (FPU) characterized by increased placental vascular resistance and respiratory acidosis. However the mechanisms of this dysfunction are not completely understood. To test the hypothesis that complement activation and neutrophil degranulation may contribute to the placental dysfunction associated with fetal bypass, we compared placental hemodynamics, complement activation, and neutrophil degranulation among fetuses exposed to cardiac bypass with a miniaturized bypass circuit including an in-line axial flow pump (Hemopump), fetuses undergoing bypass with a conventional roller pump circuit, and control fetuses that were similarly exposed but did not undergo bypass. METHODS: Twenty-six Western Cross sheep fetuses (median 122 days gestation) were randomly assigned to undergo cardiac bypass for 30 minutes with the Hemopump circuit (n = 8), to undergo bypass for 30 minutes with the conventional (roller pump) circuit (n = 10), or to undergo identical exposure and cannulation but not bypass (n = 8, controls). Blood samples were collected to measure white cell count and differential, and C3a and lactoferrin levels prior to bypass, at the end of bypass, and 1 and 2 hours after bypass. Hemodynamics and blood gases were also monitored. RESULTS: There was a fall in white cell count over time that continued after bypass in all groups; neutrophils and lymphocytes were affected similarly. C3a levels rose significantly from prebypass to postbypass in the roller pump group (p<0.0001) but not in either of the other groups. Lactoferrin levels rose significantly from start of bypass in both bypass groups (Hemopump p = 0.01; roller pump p<0.0001) but not in controls. The elevation in lactoferrin level coincided with worsening placental gas exchange and deteriorating cardiac function. CONCLUSIONS: Complement and neutrophil activation occurred with fetal cardiac bypass but only neutrophil activation mirrored the FPU and cardiac dysfunction, suggesting that products of neutrophil activation may be important contributing factors. Improved FPU function with a bypass circuit that has less extracorporeal surface and does not require a large priming volume may be due in part to a reduction in the magnitude of this inflammatory response.

Ultrasound evaluation of the inferior epigastric artery.

Color-flow Doppler ultrasound was used to assess the anatomic characteristics of the inferior epigastric artery (IEA) bilaterally in 20 nonatherosclerotic (group I; mean age, 28 years) and 20 atherosclerotic (group II; mean age, 57 years) subjects. Forty-nine percent of the IEAs were located laterally within the rectus sheath with 34% in a mid and 17% in a medial location. Seventeen percent had a large branch within 5 cm of the origin. Average length of the IEA was 10.7 +/- 3.2 cm. Average proximal and distal internal diameters were 3.0 +/- 0.45 and 1.9 +/- 0.35 mm, respectively. Neither length nor vessel diameter showed any correlation with age or body surface area. Sixty-two percent of the IEAs were greater than or equal to 9 cm in length and 1.5 mm in distal diameter. Stenosis of the vessel (more than 50% diameter) was noted at the proximal 1 cm segment in 20% of the IEAs in the atherosclerotic group but none of the IEAs in the nonatherosclerotic group. Beyond this proximal segment, there was freedom from atherosclerotic stenosis as demonstrated by the IEAs' similarity of length and diameter irrespective of age in these atherosclerotic and nonatherosclerotic populations.

Incidence and implications of systemic to pulmonary collaterals after bidirectional cavopulmonary anastomosis.

BACKGROUND: Systemic to pulmonary arterial collaterals often develop after bidirectional cavopulmonary anastomosis (BCPA). It has been proposed that such collaterals may be related to perioperative outcome and duration of effusions after the modified Fontan procedure. However, the incidence and significance of collaterals after BCPA remain uncertain. METHODS: To evaluate risk factors for, and significance of, such collaterals, we reviewed angiographic and clinical data for all 76 patients who underwent BCPA between January 1990 and June 1996 and had follow-up catheterization during or before 1997. RESULTS: The median age at BCPA was 10 months, and the median duration from BCPA to follow-up catheterization was 18 months. Arterial collaterals were detected on follow-up catheterization in 45 patients (59%). Factors associated with collateral development included a prior right-sided systemic-to-pulmonary arterial shunt, lower pre-BCPA end-diastolic ventricular pressure and pulmonary vascular resistance, and use and duration of cardiopulmonary bypass during the BCPA operation. Fourteen of the 45 patients (30%) underwent coil embolization of the collaterals. Forty-three patients have undergone extracardiac conduit Fontan, with 1 early and 1 late death. Collaterals were present in 22 of these patients, 7 of whom underwent pre-Fontan embolization. The duration from BCPA to Fontan was longer in patients with collaterals, but these patients were not more likely to have prolonged effusions than those without, and the duration of tube thoracostomy was significantly shorter in patients with collaterals. Embolization of collaterals did not affect the duration of effusions. CONCLUSIONS: Systemic-to-pulmonary arterial collaterals are common after BCPA. In contrast to prior reports, collaterals were not associated with a higher incidence of prolonged effusions after the Fontan procedure in our experience, and did not correlate with poor outcome.

Issues and outcomes in the management of supravalvar aortic stenosis.

BACKGROUND: Supravalvar stenosis of the aorta is an uncommon congenital cardiac anomaly that involves not only the supravalvar aorta but the entire aortic root. Despite considerable attention to the importance of maintaining the integrity of the aortic root during supravalvar reconstruction, there has been little focus on the management of other components of the aortic root and left ventricular outflow tract, including the aortic valve, subvalvar region, and coronary arteries. METHODS: We reviewed the records of 36 consecutive patients with supravalvar aortic stenosis who underwent repair from 1992-1998 (median age, 4 years). Discrete stenosis was present in 29 patients, whereas the remaining 7 had the diffuse form of the disease. Associated anomalies of the aortic root and adjacent structures were present in 23 patients. The median pressure gradient across the left ventricular outflow tract was 70 mm Hg. Supravalvar stenosis was relieved by extended aortoplasty with a Y-shaped patch in 18 patients, resection of the stenotic segment of ascending aorta at the sinotubular junction with end-to-end anastomosis of the ascending aorta in 7, the Ross procedure in 4, and other techniques in 7. Additional procedures included aortic valvuloplasty in 10 patients, resection of subvalvar stenosis in 11, and procedures on the coronary arteries in 2. RESULTS: There was 1 perioperative death, and no reoperations or other significant complications. During follow-up (median 33 months), there were no deaths and 3 reoperations for replacement of the aortic valve with a pulmonary autograft (n = 1) or mechanical prosthesis (n = 2). The median pressure gradient across the left ventricular outflow tract was 10 mm Hg. CONCLUSIONS: In patients with supravalvar aortic stenosis, abnormalities of the aortic valve, subaortic region, and coronary arteries are frequently present as well. Management of these issues is as critical to the long-term outcome of these patients as reconstruction of the supravalvar aorta. Aggressive valvuloplasty may help decrease the incidence of late aortic valve replacement, whereas the Ross procedure may be a preferable approach in some patients with complex outflow tract obstruction.

Neonatal repair of truncus arteriosus: continuing improvement in outcomes.

BACKGROUND: Repair of truncus arteriosus in the neonatal and early infant periods has become standard practice at many centers. We reviewed our recent experience with repair of truncus arteriosus in neonates, with a focus on early and intermediate outcomes. METHODS: From July 1992 to December 1999, 65 patients 1 month of age or less underwent primary complete repair of truncus arteriosus. Median age was 10 days, and median weight was 3.2 kg. Major associated anomalies included moderate or severe truncal valve regurgitation in 15 patients (23%), interrupted aortic arch in 8 (12%), coronary artery abnormalities in 12 (18%), and nonconfluence of the pulmonary arteries in 3 (5%). Median durations of cardiopulmonary bypass and cardioplegic arrest were 172 minutes and 90 minutes, respectively. Circulatory arrest was employed only in 7 patients undergoing concomitant repair of interrupted arch. Reconstruction of the right ventricular outflow tract was achieved with an aortic (n = 39) or pulmonary (n = 26) allograft valved conduit (median diameter, 12 mm). Replacement (n = 6) or repair (n = 5) of a regurgitant truncal valve was performed in 11 patients, and interrupted arch was repaired in 8. RESULTS: There were three early deaths (5%). Early reoperations included reexploration for bleeding in 3 patients, emergent replacement of a pulmonary outflow conduit that failed acutely in 1 patient, and placement of a permanent pacemaker in 1. Mechanical circulatory support was required in 1 patient. During the median follow-up of 32 months, there were two deaths. The Kaplan-Meier estimate of survival was 92% at 1 year and beyond. The only demographic, diagnostic, or operative factors significantly associated with poorer survival over time were operative weight of 2.5 kg or less (p = 0.01) and truncal valve replacement (p = 0.009). Actuarial freedom from conduit replacement among early survivors was 57% at 3 years. CONCLUSIONS: Repair of truncus arteriosus in the neonatal period can be performed routinely with excellent survival, even in patients with major associated abnormalities.

Wound healing after harvesting of the internal thoracic and the superior and inferior epigastric arteries.

Wound healing of sternal incisions and midline or paramedian abdominal incisions was studied at 2 weeks postoperatively in three groups of dogs. Group 1, 10 dogs, had harvesting of bilateral internal thoracic arteries, superior epigastric arteries, and inferior epigastric arteries. Group 2, 5 dogs, had removal of the same arteries, but the superior and inferior epigastric arteries were harvested through paramedian rather than midline incisions. Group 3, 5 dogs, served as control and had median sternotomies and midline abdominal incisions only. All wounds healed without complication. Wound breaking strength of the skin of the chest incisions was significantly greater (p < 0.05) in the control group (group 3) (52.6 lb) compared with groups 1 (38.0 lb) and 2 (34.8 lb). Wound breaking strength of the skin of the abdominal incisions was significantly greater (p < 0.05) in group 2 (50.4 lb) when paramedian incisions were made compared with group 1 (35.1 lb). Hydroxyproline content was similar for all groups and all incisions. We conclude that abdominal wound breaking strength is significantly greater when paramedian incisions are performed to harvest the inferior epigastric arteries. Harvesting bilateral internal thoracic, superior epigastric, and inferior epigastric arteries may lower sternal wound breaking strength.

Extracardiac conduit variation of the Fontan procedure.

The ECF operation is designed to improve postoperative outcome by enhancing factors that are critical in optimal functioning of the Fontan circulation, including preservation of ventricular and pulmonary vascular function, avoidance of dysrhythmias, and prevention of stasis and flow turbulence in the Fontan circuit. Preoperative strategies include an early bidirectional Glenn procedure, and avoiding ancillary intracardiac procedures at the time of the Fontan by performing them at the time of the Glenn operation. Operative strategies include minimizing the duration of CPB by performing the conduit to pulmonary artery anastomosis off bypass, using partial instead of full CPB by cannulating the IVC alone, avoiding hypothermia, avoiding cross-clamping of the aorta, avoiding atrial incisions and suture lines, using a tubular conduit to construct the Fontan pathway, making a large conduit to pulmonary artery anastomosis, incorporating the conduit into aggressive pulmonary arterioplasties, and offsetting of the superior and inferior cavopulmonary anastomoses.

How do food passage rate and assimilation differ between herbivorous lizards and nonruminant mammals?

What digestive adaptations permit herbivorous nonruminant mammals to sustain much higher metabolic rates than herbivorous lizards, despite gross similarity in digestive anatomy and physiology? We approached this question by comparing four herbivorous species eating the same diet of alfalfa pellets: two lizards (chuckwalla and desert iugana) and two mammals (desert woodrat and laboratory mouse). The mammals had longer small and large intestines, greater intestinal surface area, much higher (by an order of magnitude) food intake normalized to metabolic live mass, and much faster food passage times (a few hours instead of a few days). Among both reptiles and mammals, passage times increase with body size and are longer for herbivores than for carnivores. The herbivorous lizards, despite these much slower passage times, had slightly lower apparent digestive efficiencies than the mammals. At least for chuckwallas, this difference from mammals was not due to differences in body temperature regime. Comparisons of chuckwallas and woodrats in their assimilation of various dietary components showed that the woodrat's main advantage lay in greater assimilation of the dietary fiber fraction. Woodrats achieved greater fiber digestion despite shorter residence time, but possibly because of a larger fermentation chamber, coprophagy, and/or different conditions for microbial fermentation. We conclude with a comparative overview of digestive function in herbivorous lizards and mammals, and with a list of four major unsolved questions.

Percutaneous fetal access and uterine closure for fetoscopic surgery. Lessons learned from 16 consecutive procedures in pregnant sheep.

BACKGROUND: Maternal morbidity and preterm labor from fetal surgery might be minimized by a percutaneous technique for fetal access and uterine closure. METHODS: In each of 16 ewes, we inserted three trocars percutaneously into the amniotic cavity using ultrasound and fetoscopic guidance. In six ewes, percutaneous uterine closure after the procedure was attempted. We assessed feasibility and acute complications of our technique during surgery and at autopsy. RESULTS: We achieved percutaneous fetal access in 14 ewes and closed the uterus percutaneously in all six ewes attempted. Fetal injury was related to amnioinfusion or fixation of chorioamniotic membranes. Other complications were trocar dislodgment and damage to uterine wall and chorioamniotic membranes. The latter complication was prevented using balloon-tipped trocars. CONCLUSIONS: Percutaneous intraamniotic access and uterine closure for fetoscopic surgery can be achieved reliably with little maternal and fetal morbidity in sheep. Minor modifications are desired to apply this approach in humans.

Post-cardiopulmonary bypass pulmonary hypertension in lambs with increased pulmonary blood flow. A role for endothelin 1.

BACKGROUND: After cardiopulmonary bypass (CPB), pulmonary hypertension and its associated increased vascular reactivity are a major source of morbidity, particularly for children with increased pulmonary blood flow. Although post-CPB pulmonary hypertension is well described, its mechanisms remain incompletely understood. Plasma levels of endothelin 1. a potent vasoactive substance implicated in pulmonary hypertension, are increased after CPB. The purpose of the present study was threefold: to characterize the changes in pulmonary vascular resistance and vascular reactivity induced by hypothermic CPB; to investigate the effects of preexisting increased pulmonary blood flow on these changes; and to better define the role of endothelin 1 in the pathogenesis of post-CPB pulmonary hypertension. METHODS AND RESULTS: Vascular pressures and blood flows were monitored in 14 1-month-old lambs with increased pulmonary blood flow (after in utero placement of an aortopulmonary shunt) and 6 age-matched control lambs. During the 2-hour study period after 105.3 +/- 20.6 minutes of hypothermic CPB the increase in pulmonary vascular resistance was significantly augmented in lambs with increased pulmonary blood flow compared with control lambs (P < .05). Pretreatment with PD 145065 (a nonselective endothelin receptor blocker; 50 micrograms.kg-1.min-1) completely blocked this increase in pulmonary vascular resistance and blocked the increase in pulmonary vascular resistance in response to acute alveolar hypoxia after CPB (96.3 +/- 88.5% versus -9.7 +/- 16.4%; P < .05). Plasma endothelin 1 levels increased after CPB in all lambs. CONCLUSIONS: Preexisting increased pulmonary blood flow alters the response of the pulmonary circulation to hypothermic CPB; the increase in pulmonary vascular resistance induced by CPB is augmented in lambs with increased pulmonary blood flow. Pretreatment with endothelin 1 receptor blockers eliminated the increase in pulmonary vascular resistance and the pulmonary vasoconstricting response to alveolar hypoxia, suggesting a role for endothelin 1 in post-CPB pulmonary hypertension. Endothelin 1 receptor blockers may decrease morbidity in children at risk for pulmonary hypertension after surgical repair with CPB and warrants further study.