Late Clinical Outcomes of the Fontan Operation in Patients with Tricuspid Atresia

OBJECTIVE: Evaluation of the long-term clinical results of the Fontan operation in patients with tricuspid atresia. METHODS: A retrospective analysis was made at the Instituto de Cardiologia do Rio Grande do Sul (Institute of Cardiology of Rio Grande do Sul), from August 1980 through January 2000, of 25 patients with a long-term follow-up, out of a series of 36 patients who underwent the Fontan operation or one of its variants due to tricuspid atresia. Their mean age at surgery was 5.4±3.1 years, and their mean weight was 15.8±6.1 kg, the majority of them (63.9%) being males. Four patients underwent the classical Fontan operation, 12 the Kreutzer variant, 6 the Björk variant, 9 total cavopulmonary shunt with a fenestrated tube, and 5 total cavopulmonary shunt with a nonfenestrated tube. RESULTS: The patients were followed-up on an outpatient basis, with a mean long-term survival time of 5.5±4.2 years (50 days to 17.8 years) and a late mortality rate of 8%. Arterial saturation increased from 77.2±18.8% in the preoperative period to 91±6.7% upon the last outpatient visit (p>0.05). At the final check, most (67%) patients were asymptomatic and 87% could tolerate exercise. Ten (40%) patients experienced some kind of complication during the long-term follow-up, such as cardiac arrhythmia, cyanosis, protein-losing enteropathy, neurological events, right heart failure, intolerance to exercise and reoperation. CONCLUSION: The results indicate that, once the immediate postoperative period is over, during which the adaptations to the new circulatory physiology occur, the evolution of patients with tricuspid atresia who underwent the Fontan operation is satisfactory, in spite of a low, yet significant, morbidity.

Cavopulmonary anastomosis improves left ventricular assist device support in acute biventricular failure

Objective: Right ventricular failure during left ventricular assist device (WAD) support can result in severe hemodynamic compromise with high mortality. This study investigated the acute effects of cavopulmonary anastomosis on right ventricular loading and WAD performance in a model of severe biventricular failure. Methods: LVAD support was performed by means of centrifugal pump implantation in 14 anesthetized dogs (20-30 kg) with severe biventricular failure obtained by ventricular fibrillation induction. Animals were randomized to be submitted to classical cavopulmonary anastomosis (Glenn shunt) or to control group and were maintained under WAD support for 2 h. Left and right atrial, right ventricular and systemic pressures were monitored, white total pulmonary flow was simultaneously recorded by transonic flowmeters located on the superior vena cava and pulmonary trunk. Blood gas and venous lactate determinations were also obtained. Results: Ventricular fibrillation maintenance resulted in acute WAD performance impairment after 90 min in the control group, while animals with Glenn circuit maintained normal WAD pump flow (55 +/- 13 ml kg(-1) min(-1) vs 21 +/- 4 ml kg(-1) min(-1), p < 0.001) and better peripheral perfusion (blood lactate of 29 +/- 10 pg/ml vs 46 +/- 9 pg/ml, p < 0.001). Left and right atrial pressures did not change significantly, while right ventricular pressure was tower in animals with Glenn circuit (13 +/- 3 mmHg vs 22 +/- 8 mmHg, p = 0.005). Right ventricular unloading with Glenn shunt also resulted in superior total pulmonary flow (59 +/- 13 ml kg(-1) min(-1) vs 17 +/- 3 ml kg(-1) min(-1), p < 0.001). Conclusion: The concomitant use of cavopulmonary anastomosis during LVAD support in a model of severe biventricular failure limited right ventricular overloading and resulted in better hemodynamic performance. (C) 2008 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Test of a Modular Fault Current Limiter for 220 V Line Using YBCO Coated Conductor Tapes With Shunt Protection

A modular superconducting fault current limiter (SFCL) consisting of 16 elements was constructed and tested in a 220 V line for a fault current between 1 kA to 7.4 kA. The elements are made up of second generation (2G) YBCO-coated conductor tapes with stainless steel reinforcement. For each element four tapes were electrically connected in parallel with effective length of 0.4 m per element, totaling 16 elements connected in series. The evaluation of SFCL performance was carried out under DC and AC tests. The DC test was performed through pulsed current tests and its recovery characteristics under load current were analysed by changing the shunt resistor value. The AC test performed using a 3 MVA/220 V/60 Hz transformer has shown the current limiting ratio achieved a factor higher than 10 during fault of up to five cycles without conductor degradation. The measurement of the voltage for each element during the AC test showed that in this modular SFCL the quench is homogeneous and the transition occurs similarly in all the elements.

Extrahepatic portal vein thrombosis after umbilical catheterization: is it a good choice for Rex shunt?

Background: Extrahepatic portal vein thrombosis (EHPVT) is an important cause of portal hypertension in children. Rex shunt has been used successfully to treat these patients. Methods: We report our experience in 19 infants and children (5 months to 14 years) with HPVT eligible for a mesenteric-portal surgical shunt with left internal jugular vein autograft. Eight children had idiopathic EHPVT, nine had post-umbilical catheterization EHPVT, one had portal vein agenesis, and one had posttransplant EHPVT. Results: It was possible to perform the Rex shunt in all patients except for 8 of 9 cases in the post-umbilical catheterization EHPVT group. A Warren procedure was performed in 4 of those patients and a proximal splenorenal shunt in 1. Current follow-up ranges from 3 to 26 months. Shunt thrombosis occurred in one patient with portal vein agenesis and associated cardiac anomaly. Portal hypertension has significantly improved after surgery. None of our patients have experienced new bleeding episodes until now. Conclusions: The Rex shunt should be considered in the treatment of children with idiopathic EHPVT experiencing repeated gastrointestinal bleeding episodes refractory to endoscopic treatment. Nevertheless, the role of this operation for children with post-umbilical catheterization EHPVT is yet to be clearly evaluated. (C) 2011 Elsevier Inc. All rights reserved.

Long-Term Follow-Up After Successful Transjugular Intrahepatic Portosystemic Shunt Placement in a Pediatric Patient with Budd-Chiari Syndrome

Orthotopic liver transplantation is the standard of care in patients with Budd-Chiari syndrome (BCS), and transjugular intrahepatic portosystemic shunt (TIPS) has become an important adjunct procedure while the patient is waiting for a liver. No long-term follow up of TIPS in BCS patients has been published in children. We report successful 10-year follow-up of a child with BCS and iatrogenic TIPS dysfunction caused by oral contraceptive use.

Intracardiac Cavopulmonary Connection in Patients with Univentricular Heart Using Intra-atrial Lateral Tunnel and Intra-atrial Conduit Techniques

Background: In this study, we analyzed the time course of hemodynamic efficiency and follow-up in Fontan candidates who underwent the bidirectional Glenn procedure for staged intracardiac cavopulmonary connection (ICPC). Methods: Between 1991 and 2008, 52 patients with univentricular heart (mean age, 3.3 years; range, 2-8 years; 27 female patients [51.9%]) underwent ICPC. The cardiac malformations were as follows: tricuspid atresia, 25 cases (48.0%); common ventricle, 16 cases (30.7%); and pulmonary atresia with intact ventricular septum, 11 cases (21.1%). The intracardiac cavopulmonary procedure was indicated for all 52 cases. In 42 patients (80.7%), an intra-atrial lateral tunnel was constructed with a bovine pericardium patch. In the last 10 consecutive cases (19.3%), we performed a modified surgical technique in which we implanted an intra-atrial corrugated bovine pericardium tube sutured around the superior and inferior vena cava ostium. In all cases, a 4-mm fenestration was made to reduce the intratunnel pressure. All 52 patients had previously undergone a Glenn operation. Results: There were 2 hospital deaths (3.8%) and no recorded late deaths. During the follow-up, all patients were medicated with antiplatelet drugs. To evaluate the hemodynamic performance, we used Doppler echocardiography, computed tomography, and magnetic nuclear resonance studies. There were no prosthesis thromboses during this follow-up period. To evaluate cardiac arrhythmias, we conducted a Holter study. The last 10 patients with an intra-atrial conduit (IAC) presented with sinus rhythm and no arrhythmias during the last 4 years. The 50 surviving patients (96.1%) have been followed up for 6 to 204 months; all these patients are free of reoperation. Conclusion: The Glenn operation, which is performed at an early age, prepares the pulmonary bed to receive the ICPC. The midterm results of the intracardiac Fontan procedure seem to be good. The modified surgical procedure (IAC) can be a good alternative technique to the Fontan procedure in suitable patients.

Rex Shunt for Acute Portal Vein Thrombosis After Pediatric Liver Transplantation in Children With Biliary Atresia

Background/Purpose. Posttransplantation portal vein thrombosis (PVT) can have severe health consequences, and portal hypertension and other consequences of the long-term privation of portal inflow to the graft may be hazardous, especially in young children. The Rex shunt has been used successfully to treat PVT patients since 1998. In 2007, we started to perform this surgery in patients with idiopathic PVT and late posttransplantation PVT. Herein we have reported our experience with this technique in acute posttransplantation PVT. Methods. Three patients of ages 12, 15, and 18 months underwent cadaveric (n = 1) or living donor (n = 2) orthotopic liver transplantation (OLT). All patients had biliary atresia with portal vein hypoplasia; they developed acute PVT on the first postoperative day. They underwent a mesenteric-portal surgical shunt (Rex shunt) using a left internal jugular vein autograft (n = 2) or cadaveric iliac vein graft (n = 1) on the first postoperative day. Results. The 8-month follow-up has confirmed shunt patency by postoperative Doppler ultrasound. There have been no biliary complications to date. Conclusions. The mesenteric-portal shunt (Rex shunt) using an autograft of the left internal jugular or a cadaveric vein graft should be considered for children with acute PVT after OLT. These children usually have small portal veins; reanastomosis is often unsuccessful. In addition, this technique has the advantage to avoid manipulation of the hepatic hilum and biliary anastomosis. Although this study was based on a limited experience, we concluded that this technique is feasible, with great benefits to and low risks for these patients.

Hepatic Veins and Inferior Vena Cava Thrombosis in a Child Treated by Transjugular Intrahepatic Portosystemic Shunt

We report the case of a 9-year-old boy with portal hypertension, due to Budd-Chiari syndrome, and retrohepatic inferior vena cava thrombosis, submitted to a transjugular intrahepatic portosystemic shunt (TIPS) by connecting the suprahepatic segment of the inferior vena cava directly to the portal vein. After 3 months, the withdrawal of anticoagulants promoted the thrombosis of the TIPS. At TIPS revision, thrombosis of the TIPS and the main portal vein and clots at the splenic and the superior mesenteric veins were found. Successful angiography treatment was performed by thrombolysis and balloon angioplasty of a severe stenosis at the distal edge of the stent.

Rex Shunt for the Treatment of Portal Vein Thrombosis After Pediatric Liver Transplantation: A Case Report

Background and Purpose. Late portal vein thrombosis (PVT) can be extremely well tolerated, although portal hypertension and other consequences of the long-term deprivation of portal inflow to the graft may be hazardous, especially in young children. Recently, the ""Rex shunt"" has been used successfully to treat these patients. We now report the initial experience with this novel technique. Methods. A 3-year-old girl with PVT at 7 months after whole organ cadaveric liver transplant displayed portal hypertension with an episode of gastrointestinal bleeding, requiring a mesenteric-portal surgical shunt (""Rex shunt"") using a left internal jugular vein autograft. Results. Upon current follow-up of 6 months, postoperative Doppler ultrasound confirmed shunt patency. Endoscopic status was significantly improved after surgery with resolution of portal hypertension. There was no recurrence of bleeding. Conclusions. The mesenteric-portal shunt (""Rex shunt""), using a left internal jugular vein autograft, should be considered for children with late PVT after liver transplantation. Although this is an initial experience, we may conclude that this technique is feasible, with great potential benefits and low risks for these patients.

The ventriculoomental bursa shunt

Object The aim of this study is to access the efficacy of the omental bursa (lesser sac) as a receptacle of cerebrospinal fluid (CSF) and to use it as an alternative to the ventriculoatrial or ventriculopleural shunts when the peritoneum reduces or loses its CSF absorption capacity. Methods Three patients with hydrocephalus presented with malfunctioning of ventriculoperitoneal shunts, secondary to peritoneal blockage caused by previous episodes of shunt infections in two and peritonitis in one patient. All patients underwent previous shunt revisions due to ventriculitis and shunt obstruction ranging from three to eight times. In order to keep the peritoneal cavity as the main receptacle of CSF absorption site, the distal catheter was inserted in the omental bursa, through the foramen of Winslow, jointly by a pediatric surgeon. We denominated this new technique of CSF diversion as ventriculoomental bursa (VOB) shunting. The children have been followed at least for 1 year (range 12 to 28 months) with no recurrence of shunt. Conclusions VOB shunting may be considered an acceptable technique to CSF shunting when the anterior peritoneum loses or decreases its CSF absorption capacity.

Blood gases and cardiovascular shunt in the South American lungfish (Lepidosiren paradoxa) during normoxia and hyperoxia

The South American lungfish (Lepidosiren paradoxa) has an arterial P(O2), (Pa(O2)) as high as 70-100 mm Hg, corresponding to Hb-O(2) saturations from 90% to 95%, which indicates a moderate cardiovascular right to left (R-L) shunt. In hyperoxia (50% O(2)), we studied animals in: (1) aerated water combined with aerial hyperoxia, which increased Pa(O2) from 78 +/- 2 to 114 +/- 3 mm Hg and (2) and aquatic hyperoxia (50% O(2)) combined room air, which gradually increased Pa(O2) from 75 +/- 4 mm Hg to as much as 146 +/- 10 mm Hg. Further, the hyperoxia (50%) depressed pulmonary ventilation from 58 +/- 13 to 5.5 +/- 3.0 mLBTPS kg h(-1), and Pa(CO2) increased from 20 +/- 2 to 31 +/- 4 mm Hg, while pHa became reduced from 7.56 +/- 0.03 to 7.31 +/- 0.09. At the same time, venous P(O2) (Pv(O2)) rose from 40.0 +/- 2.3 to 46.4 +/- 1.2 mm Hg and, concomitantly, Pvco, increased from 23.2 +/- 1.1 to 32.2 +/- 0.5 mm Hg. R-L shunts were estimated to about 19%, which is moderate when compared to most amphibians. (C) 2010 Elsevier B.V. All rights reserved.

Limb constriction as a complication of intra-uterine vesico-amniotic shunt: Fetoscopic release

Complete fetal bladder outlet obstruction was first diagnosed in a fetus at 13.5 weeks. After sequential vesico-centesis had shown good renal function, a vesico-amniotic shunt was inserted at 17 weeks with a Rodeck catheter. The procedure was successful and amniotic fluid volume re-accumulated to normal levels. A detailed scan at 20 weeks showed that the distal free end of the catheter was wound round the left fetal thigh. As the fetus grew, there was progressive constriction of the fetal thigh by the catheter. By 29 weeks, Doppler blood flow changes to the left leg were apparent. Fetoscopic surgery was performed at 30 weeks to release the constriction. The catheter was divided successfully, but the divided end of the shunt subsequently retracted into the fetal abdomen, producing urinary ascites, bilateral hydroureter and hydronephrosis. The baby was delivered at 31.5 weeks in good condition. Endoscopic resection of anterior and posterior urethral valves was performed at 6 months of age. At 2 years, the child has normal renal function, growth parameters and developmental milestones. Mild indentation of the left thigh was still apparent, although there was no functional impairment. Copyright (C) 2002 S. Karger AG, Basel.

An efficient method for optimal location and sizing of fixed and switched shunt capacitors in large distribution systems

This paper proposes a computationally efficient methodology for the optimal location and sizing of static and switched shunt capacitors in large distribution systems. The problem is formulated as the maximization of the savings produced by the reduction in energy losses and the avoided costs due to investment deferral in the expansion of the network. The proposed method selects the nodes to be compensated, as well as the optimal capacitor ratings and their operational characteristics, i.e. fixed or switched. After an appropriate linearization, the optimization problem was formulated as a large-scale mixed-integer linear problem, suitable for being solved by means of a widespread commercial package. Results of the proposed optimizing method are compared with another recent methodology reported in the literature using two test cases: a 15-bus and a 33-bus distribution network. For the both cases tested, the proposed methodology delivers better solutions indicated by higher loss savings, which are achieved with lower amounts of capacitive compensation. The proposed method has also been applied for compensating to an actual large distribution network served by AES-Venezuela in the metropolitan area of Caracas. A convergence time of about 4 seconds after 22298 iterations demonstrates the ability of the proposed methodology for efficiently handling large-scale compensation problems.

Ventilação térmica "Féria" - tipo Shunt

As instalações de ventilação em estudo destinam-se a realizar o arejamento geral e permanente de habitações - pelo menos durante o período do ano em que a temperatura exterior obriga a manter as janelas fechadas - e a assegurar a evacuação de gases e fumos resultantes da combustão em aparelhos de aquecimento por queima (esquentadores e fogões (de uso corrente nas habitações)).