Visual light spectroscopy reflects flow-related changes in brain oxygenation during regional low-flow perfusion and deep hypothermic circulatory arrest

OBJECTIVES

Regional low-flow perfusion has been used to minimize ischemic brain injury during complex heart surgery in children. However, optimal regional low-flow perfusion remains undetermined. Visible light spectroscopy is a reliable method for continuous determination of capillary oxygen saturation (SgvO2). We used visible light spectroscopy to follow deep and superficial brain SgvO2 during cardiopulmonary bypass, regional low-flow perfusion, and deep hypothermic circulatory arrest.

METHODS

Visible light spectroscopy probes were inserted into the superficial and deep brain of neonatal (3.9-4.5 kg) piglets, targeting the caudate and thalamic nuclei. The piglets were subjected to cardiopulmonary bypass and cooled to a rectal temperature of 18 degrees C using pH stat. Regional low-flow perfusion was initiated through the innominate artery at 18 degrees C, and pump flows were adjusted to 40, 30, 20, and 10 mL/kg/min for 10-minute intervals followed by 30 minutes of deep hypothermic circulatory arrest. Regional low-flow perfusion was reestablished, and flows were increased in a stepwise manner from 10 to 40 mL/kg/min. SgvO2 was continuously monitored. Carotid flow was measured using a flow probe, and cerebral blood flow (milliliters per kilogram body weight per minute) was calculated.

RESULTS

There were no significant differences between the deep and superficial brain tissue oxygenation during regional low flow brain perfusion before deep hypothermic circulatory arrest. However, after deep hypothermic circulatory arrest, the superficial brain SgvO2 was lower than the deep brain SgvO2 (24 +/- 12 vs 55.3 +/- 8, P = .05, at flows of 30 mL/kg/min, and 34.2 +/- 17 vs 62.5 + 8, P = .06, at a flow rate of 40 mL/kg/min). During regional low-flow perfusion, SgvO2 was maintained at flows of 30 to 40 mL/kg/min (cerebral blood flows of 15 to 21 mL/kg/min and 19 to 24 mL/kg/min, respectively), but was significantly lower at pump flows of 20 mL/kg/min (cerebral blood flow of 10 to 14 mL/kg/min) and 10 mL/kg/min (cerebral blood flow of 5 to 9 mL/kg/min) compared with the values obtained just before regional low-flow perfusion (pre-deep hypothermic circulatory arrest, 37 +/- 6 vs 65.5 +/- 4.4, P < .05, and 21.6 +/- 3.7 vs 65.5 +/- 4.4, P < .01, respectively; and post-deep hypothermic circulatory arrest, 32 +/- 4.5 vs 65.5 +/- 4.4, P < .05, and 16.6 +/- 4.7 vs 65.5 +/- 4.4, P < .01, respectively).

CONCLUSIONS

Regional low-flow perfusion at pump flows of 30 to 40 mL/kg/min with resulting cerebral blood flows of 14 to 24 mL/kg/min was adequate in maintaining both deep and superficial brain oxygenation. However, lower pump flows of 20 and 10 mL/kg/min, associated with cerebral blood flow of 9 to 14 mL/kg/min, resulted in significantly reduced SgvO2 values.

The extracardiac conduit Fontan operation using minimal approach extracorporeal circulation: Early and midterm outcomes

OBJECTIVE

Our approach to the extracardiac conduit Fontan operation has evolved over time from full-pump, to partial-pump, to completely off-pump. This study is designed to report our overall experience with the extracardiac conduit Fontan operation and to evaluate the evolution in bypass technique on postoperative outcomes.

METHODS

From September 1992 to April 2005, 285 patients, median age 4.5 years (1.4-44 years), median weight 16 kg (9.4-94 kg), underwent a primary extracardiac conduit Fontan procedure. Early and late outcomes were analyzed for the entire cohort and for 2 patient groups depending on whether an oxygenator was used in the bypass circuit (166 patients; 58%) or not (119 patients; 42%).

RESULTS

Early failure (including death and takedown) occurred in 7 patients (2.5%). Prevalence of new early postoperative sinus node dysfunction necessitating a permanent pacemaker was 0.4%, and that of new tachyarrhythmias necessitating discharge home on a regimen of antiarrhythmia medications was 2.5%. Ten-year actuarial freedom from Fontan failure, new sinus node dysfunction necessitating a permanent pacemaker, and reoperation for conduit thrombosis or stenosis was 90%, 96%, and 98%, respectively. Fenestration rate was lower (P = .001) in the no-oxygenator group (8%) than in the oxygenator group (25%). Patients in the no-oxygenator group had lower intraoperative Fontan pressure (12.0 +/- 2.3 vs 13.5 +/- 2.4 mm Hg, P < .001), common atrial pressure (4.6 +/- 1.8 vs 5.3 +/- 1.8 mm Hg, P = .003), and transpulmonary gradient (7.5 +/- 2.1 vs 8.3 +/- 2.2 mm Hg, P = .013) than did the oxygenator group.

CONCLUSIONS

The extracardiac conduit Fontan operation coupled with minimal use of extracorporeal circulation is associated with favorable intraoperative hemodynamics, low fenestration rate, minimal risk of thrombosis or stenosis, and minimal early and late rhythm disturbance.

Esophageal saturation during antegrade cerebral perfusion: a preliminary report using visible light spectroscopy

BACKGROUND

Visible light spectroscopy (VLS) is newer technology that measures real-time tissue oxygenation. It has been validated in detecting mucosal ischemia in adults. During complex neonatal heart surgery, antegrade cerebral perfusion (ACP) maintains cerebral saturation. Whether ACP maintains peripheral tissue perfusion in humans is not known.

METHODS

Five patients undergoing neonatal open heart surgery with hypothermic cardiopulmonary bypass (CPB) were studied using a VLS esophageal probe in addition to bilateral near infrared cerebral oximetry. Three of five patients required ACP for arch repair, while two patients did not. VLS and cerebral saturation data were collected and analyzed in 5 min intervals prior to CPB, during CPB, and during ACP.

RESULTS

In the two patients undergoing heart surgery with routine hypothermic CPB, both cerebral and esophageal saturations were maintained. However in all three neonates requiring ACP, although cerebral saturations did not decrease, esophageal saturation fell below the ischemic threshold (35%). Following establishment of normal CPB, esophageal saturation returned to baseline.

CONCLUSIONS

Antegrade cerebral perfusion maintains cerebral oxygen delivery, however, it does not adequately perfuse the esophagus in neonates. This could have clinical implications.

Aortopulmonary window with anomalous origin of the right coronary artery from the pulmonary artery: Two cases highlighting the importance of complete pre-operative echocardiographic evaluation of the coronary arteries in all conotruncal anomalies

This report describes two infants with an aortopulmonary window in association with anomalous origin of the right coronary artery from the pulmonary artery. In both cases the diagnosis was made pre-operatively by transthoracic echocardiography, with the initial clue being extensive collateral flow within the myocardium. In each case there was surgical confirmation of the echocardiographic findings. These two cases demonstrate that coronary artery evaluation should be an integral part of every new echocardiographic evaluation, particularly in the setting of conotruncal anomalies.

Coarctation of the aorta in the right aortic arch with left aberrant innominate artery

Right aortic arch with an aberrant left innominate artery is a rare combination. We report a unique case of coarctation of the aorta in a patient with right aortic arch and aberrant left innominate artery. The diverticulum of Kommerell gave rise to the left innominate artery and a left ligamentum arteriosum, completing a vascular ring. This unusual case raises interesting points regarding the development of coarctation in the context of a right-sided arch and the approach to management of these patients.

Unifocalization of Major Aortopulmonary Collaterals in Single-Ventricle Patients

BACKGROUND

Unifocalization of major aortopulmonary collateral arteries (MAPCAs) in pulmonary atresia with ventricular septal defect and intracardiac repair has become the standard of care. However, there are no reports addressing unifocalization of MAPCAs in single-ventricle patients. It is unknown whether their pulmonary vascular bed can be reconstructed and low enough pulmonary vascular resistance achieved to allow for superior or total cavopulmonary connections.

METHODS

We reviewed data on all patients with functional single ventricles and unifocalization procedures of MAPCAs. From 1997 to 2005, 14 consecutive children with various single-ventricle anatomies were operated on.

RESULTS

Patients had a median of three surgical procedures (range, 1 to 5). Two patients had absent, all others diminutive central pulmonary arteries, with an average of 3.5 +/- 1.2 MAPCAs. Seven patients (50%) had bidirectional Glenn procedures, and 3 of these had Fontan procedures. Median postoperative pulmonary artery pressures measured 12.5 mm Hg (Glenn) and 14 mm Hg (Fontan), respectively. Six patients are alive today (46%), with 1 patient lost to follow-up. Three patients died early and 3 late after initial unifocalization to shunts. One other patient survived unifocalization, but was not considered a candidate for a Glenn procedure and died after high-risk two-ventricle repair. Another patient with right-ventricle-dependent coronary circulation died of sepsis late after Glenn.

CONCLUSIONS

In selected patients with functional single ventricles and MAPCAs, the pulmonary vascular bed can be reconstructed sufficiently to allow for cavopulmonary connections. Venous flow to the pulmonary vasculature decreases cardiac volume load and is likely to increase life expectancy and quality of life for these patients.

Homograft valved right ventricle to pulmonary artery conduit as a modification of the Norwood procedure

BACKGROUND

The use of a right ventricle to pulmonary artery (RV-PA) conduit in the Norwood procedure has been proposed to increase postoperative hemodynamic stability. A valve within the conduit should further decrease RV volume load. We report our clinical experience with this modification.

METHODS AND RESULTS

From February 2002 through August 2005, we performed 88 consecutive Norwood procedures using RV-PA conduits. We used composite valved conduits made from cryopreserved homograft and polytetrafluoroethylene (PTFE) in 66 cases (54 pulmonary, 12 aortic homografts), other valved conduits in 14, and unvalved PTFE in 8 cases. Hospital survival was 88.6% overall and increased to 93.1% after the initial year. Early interventions were required in 18 patients (16 for cyanosis). Prestage II cardiac catheterization was performed at a mean age of 126 days. Mean Qp/Qs was 1, with mean aortic saturation 71%, mean O2 extraction 24%, and mean right ventricular end-diastolic pressure 9 mm Hg. Patient weight, use of an aortic homograft valve in the conduit, stage I palliation within the first year of our experience, and low O2 extraction and high transpulmonary gradient prestage II were risk factors for overall death. Early interventions were more frequent in aortic valve conduits compared with all other conduits.

CONCLUSIONS

The valved RV-PA conduit was associated with low early mortality after the Norwood procedure. The majority of these patients had normal cardiac output and well-maintained RV function. There may be a higher risk for early conduit interventions and death when aortic valve homografts are used in the RV-PA conduit.

Profile of serum S100beta levels during maturation in fetal and neonatal sheep

Serum levels of the protein S-100beta are dependent on three factors: rate of production, permeability of the blood-brain barrier, and rate of clearance. In the developing fetus and neonate all of these factors change at different rates. This study was performed to determine how serum S-100 levels varied during fetal and early postnatal life. Blood samples were obtained from 41 fetal and neonatal lambs. The blood was separated in a centrifuge and the serum drawn off and assayed for S-100beta using a commercially available radioimunoassay kit. S-100beta did not appear in the blood until halfway through pregnancy. Thereafter, levels steadily increased until 1 month after birth. Following this, S-100beta levels decreased progressively until by 1 year of age, they had reached a plateau. S-100beta levels change significantly with normal fetal and neonatal maturation. Valid interpretation of other data from subjects of similar developmental stage must take into consideration this physiological variation.

Neonatal Brain Protection and Deep Hypothermic Circulatory Arrest: Pathophysiology of Ischemic Neuronal Injury and Protective Strategies

Deep hypothermic circulatory arrest (DHCA) has been used for the past 50 years in the surgical repair of complex congenital cardiac malformations and operations involving the aortic arch; it enables the surgeon to achieve precise anatomical reconstructions by creating a bloodless operative field. Nevertheless, DHCA has been associated with immediate and late neurodevelopmental morbidities. This review provides an overview of the pathophysiology of neonatal hypoxic brain injury after DHCA, focusing on cellular mechanisms of necrosis, apoptosis, and glutamate excitotoxicity. Techniques and strategies in neonatal brain protection include hypothermia, acid base blood gas management during cooling, and pharmacologic interventions such as the use of volatile anesthetics. Surgical techniques consist of intermittent cerebral perfusion during periods of circulatory arrest and continuous regional brain perfusion.

Preliminary results of fetal cardiac bypass in nonhuman primates

OBJECTIVE

Fetal cardiac surgery has potential benefits for treatment of some congenital heart defects. However, placental dysfunction as a result of fetal bypass, fetal stress, and fetal exposure to external milieu needs to be overcome to optimize the outcomes of fetal cardiac bypass. In this study we evaluated the technical feasibility of cardiac bypass in the nonhuman primate fetus and the efficacy of different anesthetic approaches.

METHODS

Twelve baboon fetuses, average gestation 146 +/- 8 days and weight 696 +/- 184 g, were used. Three fetuses were excluded from the study because of nuchal cord presentations. The animals were separated into two anesthesia groups: isoflurane (n = 6) and fentanyl and midazolam (n = 3). A miniature roller pump circuit without oxygenator was used for fetal bypass for 30 minutes. No blood transfusion was performed. Fetal blood gas samples were collected before bypass, during bypass, and at 15 and 60 minutes after bypass.

RESULTS

All fetuses in the isoflurane group were successfully placed on the cardiac bypass circuit. However, 2 animals in the fentanyl and midazolam group were not placed on the bypass circuit because of sustained elevation in maternal uterine tone. All maternal baboons survived. Of the 6 fetuses in the isoflurane group, 5 survived for 60 minutes; however, placental function continued to deteriorate after bypass (Pa o 2 33 +/- 3 mm Hg before bypass, 23 +/- 6 mm Hg 15 minutes after, and 18 +/- 9 mm Hg 60 minutes after).

CONCLUSION

The technical feasibility of cardiac bypass in nonhuman primate fetuses weighing less than 1000 g was confirmed. Isoflurane anesthesia appears to be superior to fentanyl and midazolam anesthesia for fetal cardiac surgery because of adequate uterine relaxation.

Pulmonary expression of the hepatocyte growth factor receptor c-Met shifts from medial to intimal layer after cavopulmonary anastomosis

OBJECTIVE

Pulmonary arteriovenous malformations occur in up to 60% of patients after cavopulmonary anastomosis. We compared the effects of cavopulmonary anastomosis and pulmonary artery banding on lung gene expression in an ovine model to study the abnormal pulmonary vascular remodeling after the exclusion of inferior vena caval blood independent of reduced pulmonary blood flow. We previously demonstrated by contrast echocardiography that pulmonary arteriovenous malformations develop by 8 weeks after cavopulmonary anastomosis but not after pulmonary artery banding. Hepatocyte growth factor, a pleiotropic factor with morphogenic, mitogenic, and angiogenic activities, signals via its specific receptor c-Met to induce the antiapoptotic factor Bcl-2. In this study, we examined pulmonary artery expression of these factors and their potential role in pulmonary artery remodeling after cavopulmonary anastomosis and pulmonary artery banding.

METHODS

Eighteen lambs aged 35 to 45 days were placed into 3 groups: cavopulmonary anastomosis, pulmonary artery banding, and control (n = 6/group). In the cavopulmonary anastomosis group, the superior vena cava was anastomosed to the right pulmonary artery in an end-to-end fashion. In the pulmonary artery banding group, the left pulmonary artery was banded to reduce blood flow to 20% of control. The control group had a simple right pulmonary artery clamp for 30 minutes. Lung was harvested for Western blot, reverse transcriptase-polymerase chain reaction, and immunostaining at 2 weeks (n = 3/group) and 5 weeks (n = 3/group) after surgery.

RESULTS

The expression of c-Met mRNA after cavopulmonary anastomosis was increased by twofold compared with the control or pulmonary artery banding group. The total lung expression of c-Met by Western blot was also up regulated at 2 weeks (P <.05). However, total lung expression of hepatocyte growth factor and Bcl-2 by Western and reverse transcriptase-polymerase chain reaction was not different from the control and pulmonary artery banding groups at both 2 and 5 weeks after surgery. Immunohistochemical analysis revealed that c-Met expression was localized to the intimal layer of the pulmonary artery in the cavopulmonary anastomosis, while its expression in the control and pulmonary artery banding lungs was localized to the medial layer. Localization of Bcl-2 on the intimal layer in lambs with cavopulmonary anastomosis followed the same pattern as c-Met.

CONCLUSIONS

After cavopulmonary anastomosis, pulmonary artery expression of the hepatocyte growth factor receptor c-Met and one of its downstream effectors, Bcl-2, had increased in the intimal layer and decreased in the medial layer. Because the hepatocyte growth factor signaling promotes increased endothelial cell survival, it may have a role in pulmonary artery remodeling following cavopulmonary anastomosis. In addition, the change of c-Met expression in the medial layer after cavopulmonary anastomosis suggests a possible mechanism for the smooth muscle cell alteration related to abnormal angiogenesis.

A method for selectively limiting lumen diameter in corrosion casting

Corrosion casting is a technique frequently used to evaluate the form and spatial relationship of three dimensional biological structures, such as vascular networks, in vitro [Scann. Microsc. 5 (1991) 1097; Schraufnagel, D.E. The lung microstructure. In: Motta, P.M., Murakami, T. Fujita, H. eds. Scanning Electron Microscopy of Vascular Casts: Methods and Applications. Boston: Kluwer Academic Publishers; 1992:123-137]. However, because corrosion casts tend to reproduce the complexity of surrounding vascular structures as well as the structures of interest, the use of this technique in highly complex vascular systems may obscure important changes such as A-V shunts because they may get lost among the myriad of capillaries. We developed a novel modification for creating vascular corrosion casts by utilizing polystyrene microspheres to selectively embolize normal capillary networks and thereby reduce the overall complexity of the cast. his technique may aid investigators in the evaluation of a variety of vascular beds and is useful in demonstrating non-capillary arteriovenous communications.

Arch reconstruction without circulatory arrest: current clinical applications and results of therapy

Laboratory and clinical data have confirmed the deleterious effects of deep hypothermic circulatory arrest. Long-term data and rigorous neuropsychiatric data are currently sparse, but that which are available show adverse outcomes following circulatory arrest, and therefore support the use of continuous perfusion techniques. There are no available long-term data on continuous perfusion techniques with respect to neurologic outcomes, but using these techniques the incidence of postoperative seizures or other neurologic events is rare. Currently available bypass systems and microsurgical techniques have allowed continuous flow and regional perfusion to become practical alternatives. Several innovative techniques for avoiding circulatory arrest during neonatal aortic arch reconstruction for univentricular and biventricular hearts are described. It would appear prudent and desirable to provide continuous perfusion now that long-term survival after repair of even the most complex cardiac anomalies including single ventricle defects is commonplace.

Neonatal truncus arteriosus repair: surgical techniques and clinical management

Truncus arteriosus is now ideally repaired in the neonatal period with low morbidity and mortality. Published reports have documented mortality rates in the range of 4% to 5% with mean age at repair as low as 11 days. The physiologic basis for improved outcomes with earlier repair is the avoidance of damaging sequelae of pulmonary overcirculation and heart failure. Data show that baseline mean pulmonary artery pressure is lower in infants undergoing earlier repair. Improved operative outcomes also have been achieved with aggressive truncal valve repair versus replacement in the presence of truncal valve dysfunction, right ventricular outflow tract reconstructive techniques that are patient anatomy-specific, and use of regional perfusion techniques for repair of associated interrupted aortic arch. In addition, a heightened awareness of anomalies of coronary artery ostial location, number, angle of takeoff, and degree of patency can result in avoidance of inadvertent injury to the artery and associated myocardial insult.

Effect of enalaprilat on postoperative hypertension after surgical repair of coarctation of the aorta

OBJECTIVE

Hypertension in pediatric patients after surgical repair of coarctation of the aorta can be difficult to control and may lead to morbidity. The renin-angiotensin system mediates at least part of this hypertension. Enalaprilat, the only intravenous angiotensin-converting enzyme inhibitor, is used to treat hypertension in pediatric patients in other settings. However, its effect on postoperative hypertension during the early postoperative period in patients undergoing surgical repair of coarctation of the aorta is unknown.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Operating room and the pediatric intensive care unit.

PATIENTS

Fourteen consecutive pediatric patients between the ages of 1 and 18 yrs scheduled to undergo surgical repair of coarctation of the aorta.

INTERVENTIONS

Patients were randomized to receive enalaprilat or saline placebo. Infusions were begun intraoperatively within 15 mins of aortic repair and repeated every 6 hrs.

MEASUREMENTS AND MAIN RESULTS

Plasma renin activity was measured at baseline and on postoperative day 1. Blood pressure was determined at 30 mins and at 2, 4, and 6 hrs after infusion and scored relative to the preoperative blood pressure. The blood pressure in the enalaprilat group was consistently lower at 30 mins, 2 hrs, and 4 hrs after infusion (p <.05), but not at 6 hrs. Plasma renin activity was significantly lower in the placebo group on postoperative day 1. Length of stay in the pediatric intensive care unit trended shorter in the treated group.

CONCLUSIONS

Conclusions are limited by a small cohort. Angiotensin-converting enzyme inhibitor therapy resulted in improved blood pressure control after coarctation repair. Further improvement of blood pressure control may be achievable by use of a larger dose of enalaprilat or a 4-hr enalaprilat-dosing interval.

Fetal myocardial protection is markedly improved by reduced cardioplegic calcium content

BACKGROUND

Fetal cardiac surgery holds a clear therapeutic benefit in the treatment of lesions that increase in complexity due to pathologic blood flow patterns during development. Fetal and neonatal myocardial physiology differ substantially, particularly in the regulation of myocardial calcium concentration. To examine issues of calcium homeostasis and fetal myocardial protection, a novel isolated biventricular working fetal heart preparation was developed.

METHODS

Hearts from 20 fetal lambs, 115 to 125 days gestation, were harvested and perfused with standard Krebs-Henseleit (K-H) solution. The descending aorta was ligated distal to the ductal insertion and the branch pulmonary arteries were ligated to mimic fetal cardiovascular physiology. Hearts were arrested for 30 minutes with normocalcemic (n = 8), hypocalcemic (n = 6), or hypercalcemic (n = 6) cold crystalloid cardioplegia before reperfusion with K-H solution.

RESULTS

Compared with normocalcemic cardioplegia, hypocalcemic cardioplegia improved preservation of left ventricular (LV) systolic function (88% +/- 2.2% vs 64% +/- 15% recovery of end-systolic elastance, p = 0.02), diastolic function (12% +/- 21% vs 38% +/- 11% increase in end-diastolic stiffness, p = 0.04), and myocardial contractility (97% +/- 9.6% vs 75.2% +/- 13% recovery of preload recruitable stroke work [PRSW], p = 0.04). In contrast, the fetal myocardium was sensitive to hypercalcemic arrest with poor preservation of LV systolic function (37.5% +/- 8.4% recovery of elastance), diastolic function (86% +/- 21% increased stiffness), and overall contractility (32% +/- 13% recovery of PRSW). Myocardial water content was reduced in hearts arrested with hypocalcemic cardioplegia (79% +/- 1.8% vs 83.7% +/- 0.9%, p = 0.0006).

CONCLUSIONS

This study demonstrates the sensitivity of the fetal myocardium to cardioplegic calcium concentration. Hypocalcemic cardioplegia provides superior preservation of systolic, diastolic, and contractile function of the fetal myocardium.

Induced fibrillation is equally effective as crystalloid cardioplegia in the protection of fetal myocardial function

BACKGROUND

Fetal cardiac intervention represents a potential advance in the treatment of congenital cardiac lesions that increase in complexity during development. Prenatal repair of a primary defect might prevent pathologic blood-flow patterns that can result in hypoplasia of a cardiac chamber or great vessel. However, strategies to optimize fetal myocardial protection have not been studied. A biventricular working fetal heart preparation was used to evaluate the cardioprotective properties of induced fibrillation and crystalloid cardioplegia.

METHODS

Hearts from 16 fetal lambs at 115 to 125 days' gestation were harvested and perfused with Krebs-Henseleit solution. The descending aorta was ligated distal to the ductal insertion and the branch pulmonary arteries were ligated to simulate the parallel circulation of the fetus. Hearts were arrested with normothermic fibrillation (n = 8) or hypothermic crystalloid cardioplegia (n = 8) before reperfusion with Krebs-Henseleit solution. Baseline and postarrest myocardial function measurements were obtained from analysis of pressure-dimension relationships.

RESULTS

Fibrillatory and cardioplegic arrest were equally effective at preserving postarrest systolic function (left ventricle, 70% +/- 5% vs 68% +/- 15%, P =.52; right ventricle, 68% +/- 4.5% vs 65% +/- 4.5%, P =.26) and preventing increased diastolic stiffness (left ventricle, 32% +/- 5.3% vs 38% +/- 11%, P =.24; right ventricle, 25% +/- 3.3% vs 27% +/- 2.1%, P =.46). Myocardial water content was unchanged in hearts arrested with fibrillation and cardioplegia (84% +/- 1.5% vs 83.7% +/- 0.9%, P =.71).

CONCLUSIONS

Normothermic fibrillation and hypothermic crystalloid cardioplegia provide equal protection of the fetal myocardium. In the setting of diminished fetal myocardial reserve and because of the limited ability to manipulate the surrounding temperature in the fetus, normothermic fibrillation may be preferable for in utero repairs of selected congenital heart defects.

Electrical resynchronization: a novel therapy for the failing right ventricle

BACKGROUND

Many patients with congenital heart disease develop right ventricular (RV) failure due to anatomy and prior therapy. RV problems may include right bundle-branch block (RBBB), volume loading, and chamber enlargement. Because the failing RV may have regional dyskinesis, we hypothesized that resynchronization therapy might augment its performance.

METHODS AND RESULTS

We studied 7 patients with RV dysfunction and RBBB, using a predefined pacing protocol. QRS duration, cardiac index (CI), and RV dP/dt were measured in 4 different pacing states. Atrioventricular pacing improved CI and RV dP/dtmax and decreased QRS duration as compared with atrial pacing or sinus rhythm.

CONCLUSIONS

Atrioventricular pacing in patients with RBBB and RV dysfunction augments RV and systemic performance. RV resynchronization is a promising novel therapy for patients with RV failure.

Robotic-assisted endoscopic thoracic aortic anastomosis in juvenile lambs

BACKGROUND

Advances in robotic technology have enabled a wider range of applications for minimally invasive techniques in cardiac surgery, including mitral valve repair and coronary artery bypass grafting. With increased technical sophistication, robotic-assisted techniques can be developed for the endoscopic repair of certain congenital cardiac lesions.

OBJECTIVE

The purpose of this study was to assess the feasibility of closed chest thoracic aortic anastomosis in a juvenile ovine model.

METHODS

Lambs, aged 45 to 55 days, underwent surgery that was performed using the da Vinci robotic surgical system. Using 3 ports, the surgeon dissected the descending thoracic aorta and mobilized it free from attachments, using single-lung ventilation and CO2 insufflation. Snares were introduced through 2 stab wounds for aortic occlusion proximally and distally. In 4 lambs, the aorta was completely transected and reanastomosed using interrupted nitinol sutures. One lamb underwent longitudinal aortotomy, and patch aortoplasty was performed with the placement of a Gore-Tex patch. Snares were released and the animals were recovered once hemodynamically stable. Animals were sacrificed at 6 to 12 hours after surgery and the descending aorta was harvested. Burst-pressure testing was performed on the anastomoses.

RESULTS

All 5 lambs survived the procedure with stabilization of hemodynamic parameters following surgery. The mean aortic clamp time was 47 +/- 17 minutes, and the anastomosis was completed in 26 +/- 5 minutes. The mean burst pressure was 163 +/- 9 mm Hg.

CONCLUSIONS

Endoscopic thoracic aortic anastomosis can be performed safely and with adequate exposure in a juvenile large-animal model using computer-assisted surgical techniques. With further refinements, these approaches could be applied to the repair of congenital anomalies of the aorta, including interrupted aortic arch and aortic coarctation.

Intermediate term follow-up of the end-to-side aortic anastomosis for coarctation of the aorta

BACKGROUND

Classic techniques for repairing coarctation of the aorta, especially in neonates, have a significant incidence of recurrent obstruction. By connecting the descending aorta to the proximal aortic arch, the end-to-side aortic anastomosis isolates hypoplastic distal arch and encroaching ductal tissue from the anastomotic site.

METHODS

Follow-up data were available for 88 patients (54 male) who underwent an end-to-side aortic anastomosis from November 1992 until November 1999. The median postoperative follow-up was 1.9 years (range, 0.1 to 6.3 years). Fifty-four patients were corrected as neonates. Thirty-four patients were operated on out of the neonatal period (> 1 month of age). A systolic blood pressure gradient > or = 20 mm Hg and a Doppler flow velocity > or = 2.5 ms across the area of repair were considered a recurrent obstruction.

RESULTS

No patients in the pediatric group had a recurrent obstruction. In the neonatal group, 3 patients (5.5%) had recurrent obstruction. Of those, 2 patients had a reintervention performed; one reintervention was a balloon angioplasty and the other one was a reoperation. Kaplan-Meier analysis of the neonatal group revealed a 95.8% freedom from reintervention at 1 and 2 years.

CONCLUSIONS

The end-to-side aortic anastomosis is an effective repair for coarctation of the aorta. Even when performed in the neonatal period, recurrence of coarctation is rare.

The role of oxidative stress in the development of pulmonary arteriovenous malformations after cavopulmonary anastomosis

BACKGROUND

Cavopulmonary anastomosis is used for palliation of cyanotic heart disease. Clinically significant pulmonary arteriovenous malformations occur in up to 25% of patients after surgical intervention. Cavopulmonary anastomosis creates several modifications to pulmonary physiology that may contribute to the development of pulmonary arteriovenous malformations, including reduced pulmonary blood flow and the exclusion of inferior vena caval effluent.

OBJECTIVE

By comparing the expression of angiogenic and stress-related proteins after cavopulmonary anastomosis and pulmonary artery banding, we sought to determine which genes were upregulated independent of reduced pulmonary blood flow.

METHODS

Lambs aged 35 to 45 days were placed into 1 of 3 groups: cavopulmonary anastomosis (n = 6), pulmonary artery banding (n = 6), and sham control (n = 6) animals. In our model pulmonary arteriovenous malformations are detectable by means of bubble-contrast echocardiography 8 weeks after cavopulmonary anastomosis. Lung tissue was harvested for Western blotting at 2 and 5 weeks after surgery.

RESULTS

Cavopulmonary anastomosis and pulmonary artery banding both increased angiogenic gene expression, but only cavopulmonary anastomosis induced the expression of endothelial stress-related genes. Vascular endothelial growth factor was upregulated 2.5-fold after both cavopulmonary anastomosis (P =.002) and pulmonary artery banding (P =.007). Only cavopulmonary anastomosis upregulated 2 stress-related genes, HO1 and GLUT1, 2.7-fold (P =.002) and 3.8-fold (P =.03), respectively. Hypoxia-inducible factor was upregulated 4-fold (P =.003) after cavopulmonary anastomosis. Pulmonary artery banding failed to induce the increased expression of any of these proteins.

CONCLUSIONS

Reduced pulmonary blood flow induces a pulmonary angiogenic response but not an endothelial stress response. These results suggest that oxidative stress is more relevant to the formation of pulmonary arteriovenous malformations than angiogenic signaling alone because pulmonary artery banding does not result in pulmonary arteriovenous malformations. Oxidative stress of the pulmonary endothelium resulting from cavopulmonary anastomosis may predispose the affected vasculature to arteriovenous shunting.