Common arterial trunk in functionally univentricular hearts: a case series

INTRODUCTION

The association of a univentricular heart defect with common arterial trunk is extremely rare. There is a lack of population-based outcome studies reported in the literature.

METHODS

The hospital records, echocardiographic and other imaging modality data, outpatients' records, operation notes, and other electronic data were reviewed. Patients were reviewed, and the final outcomes of surgery were observed.

RESULTS

Six cases (two males) with common arterial trunk presented over a 30-year period. Five had a complete unbalanced atrioventricular septal defect (83%) and one (17%) had tricuspid atresia associated with common arterial trunk. All had antenatal diagnosis. Two cases (33%) were excluded from initial surgical palliation due to Trisomy 21 in one and severe truncal valve regurgitation in one. Initial surgical palliation was performed in four cases (67%) at median age of 31 days (2-60) and consisted of disconnection and reconstruction of the pulmonary arteries and establishing controlled pulmonary blood flow. There were no early deaths. Conversion to cavopulmonary shunt was not possible in two due to severe airway problems in one and pulmonary arteries anatomy in one. They died at 11 and 16 months, respectively. Two patients (33%) underwent cavopulmonary shunt with 1 (17%) being alive at 18 months - 12 months after cavopulmonary shunt. The second patient proceeded to Fontan completion at 19 months but required catheter takedown 3 months later and died 3.5 years later.

CONCLUSIONS

Univentricular hearts with common arterial trunk carry extremely poor short- to medium-term outcomes. This should inform antenatal and postnatal counselling and decision-making.

Heart failure in single right ventricle congenital heart disease: physiological and molecular considerations

Because of remarkable surgical and medical advances over the past several decades, there are growing numbers of infants and children living with single ventricle congenital heart disease (SV), where there is only one functional cardiac pumping chamber. Nevertheless, cardiac dysfunction (and ultimately heart failure) is a common complication in the SV population, and pharmacological heart failure therapies have largely been ineffective in mitigating the need for heart transplantation. Given that there are several inherent risk factors for ventricular dysfunction in the setting of SV in addition to probable differences in molecular adaptations to heart failure between children and adults, it is perhaps not surprising that extrapolated adult heart failure medications have had limited benefit in children with SV heart failure. Further investigations into the molecular mechanisms involved in pediatric SV heart failure may assist with risk stratification as well as development of targeted, efficacious therapies specific to this patient population. In this review, we present a brief overview of SV anatomy and physiology, with a focus on patients with a single morphological right ventricle requiring staged surgical palliation. Additionally, we discuss outcomes in the current era, risk factors associated with the progression to heart failure, present state of knowledge regarding molecular alterations in end-stage SV heart failure, and current therapeutic interventions. Potential avenues for improving SV outcomes, including identification of biomarkers of heart failure progression, implications of personalized medicine and stem cell-derived therapies, and applications of novel models of SV disease, are proposed as future directions.

Velocity vector imaging for the assessment of segmental ventricular function in children with a single right ventricle after cavopulmonary anastomosis

OBJECTIVE

Ventricular function assessment is very important for the treatment and prognostic classification of children with a single right ventricle (SRV) after cavopulmonary anastomosis (CPA). However, unusual ventricular shapes can result in inaccurate measurements. The aim of this study was to evaluate velocity vector imaging (VVI) for assessing segmental ventricular function in children with SRV after CPA.

METHODS

Twenty-one children with SRV after CPA and 21 age- and sex-matched children with normal biventricular anatomy and function were included. The longitudinal velocity, displacement, strain and strain rate were measured in the two groups in six segments by VVI. The velocity, displacement, strain and strain rate of the SRVs were compared with max(dp/dt) measured during simultaneous cardiac catheterization in the SRV subjects.

RESULTS

The control group consisted of 13 males and 8 females (69% males) with a mean age of 6.7 ± 3.5 years and mean weight of 20.5 ± 6.5 kg, and the study group consisted of 13 males and 8 females with a mean age 6.7 ± 3.7 years and mean weight of 20.6 ± 6.8 kg. Age, weight and sex distribution were similar between the groups (all, p > .05). Strain and strain rate values in all six segments were significantly lower in the study group than in the control group (all, p < .05). The max(dp/dt) of the SRV was 522.84 ± 158.32 mmHg/s, and the strain rate of the basal segment at the rudimentary chamber correlated best with max(dp/dt) (r = 0.74, p < .01).

CONCLUSIONS

Segmental ventricular dysfunction was present in children with SRV after CPA, and it could be assessed using VVI.

Early Diagnostic Features of Left-to-Right Shunt-Induced Pulmonary Arterial Hypertension in Piglets

BACKGROUND

We aimed to establish early diagnostic characteristics of left-to-right shunt-induced pulmonary arterial hypertension (PAH) in a piglet model.

METHODS

A shunt-induced PAH in piglets (n = 9) was successfully established by anastomosis of vascular prosthesis from aorta to pulmonary artery with follow-up for 6 months by a number of diagnostic procedures.

RESULTS

PAH developed with mean pulmonary arterial pressure [PAP] of 30.2 ± 6.0 mm Hg immediately after operation and 33.5 ± 8.7 mm Hg at 3 months after operation with pulmonary vascular resistance increased to 4.0 ± 0.9 Wood units. There was a weak correlation on systolic PAP between catheterization and echocardiography but the Tei index was significantly correlated to systolic PAP. Magnetic resonance imaging demonstrated that the end-diastolic volume index, systolic volume index, ejection fraction of the ventricle, and ventricular mass index were sensitive indices. Technetium-99m single-photon emission computed tomography indicated increased blood flow in the upper and middle zones of both lungs. Positron emission tomography-computed tomography (PET-CT) demonstrated a higher kilo count (kct) of ¹⁸F-fluorodeoxyglucose in the right ventricular wall and both chambers at 3 months postoperatively (right ventricular wall: 5,708.3 ± 428.4 versus 3,965.5 ± 138.6 preoperatively, p = 0.003; both chambers: 2,963.6 ± 219.4 versus 1,710.1 ± 35.4 preoperatively, p < 0.05) as well as at 6 months for both chambers (p < 0.05).

CONCLUSIONS

In this successful left-to-right shunt-induced PAH model in piglets, sensitive indices including the Tei index, systolic volume index, ejection fraction, ventricular mass index, lung perfusion, and glycometabolism by PET-CT in early PAH are determined. For the first time, we report that glycometabolism by PET-CT is useful in early diagnosis. These indices may be used for the early diagnosis in the left-to-right shunt-induced PAH.

Cardiac performance and quality of life in patients who have undergone the Fontan procedure with and without prior superior cavopulmonary connection

BACKGROUND

A superior cavopulmonary connection is commonly performed before the Fontan procedure in patients with a functionally univentricular heart. Data are limited regarding associations between a prior superior cavopulmonary connection and functional and ventricular performance late after the Fontan procedure.

METHODS

We compared characteristics of those with and without prior superior cavopulmonary connection among 546 subjects enrolled in the Pediatric Heart Network Fontan Cross-Sectional Study. We further compared different superior cavopulmonary connection techniques: bidirectional cavopulmonary anastomosis (n equals 229), bilateral bidirectional cavopulmonary anastomosis (n equals 39), and hemi-Fontan (n equals 114).

RESULTS

A prior superior cavopulmonary connection was performed in 408 subjects (75%); the proportion differed by year of Fontan surgery and centre (p-value less than 0.0001 for each). The average age at Fontan was similar, 3.5 years in those with superior cavopulmonary connection versus 3.2 years in those without (p-value equals 0.4). The type of superior cavopulmonary connection varied by site (p-value less than 0.001) and was related to the type of Fontan procedure. Exercise performance, echocardiographic variables, and predominant rhythm did not differ by superior cavopulmonary connection status or among superior cavopulmonary connection types. Using a test of interaction, findings did not vary according to an underlying diagnosis of hypoplastic left heart syndrome.

CONCLUSIONS

After controlling for subject and era factors, most long-term outcomes in subjects with a prior superior cavopulmonary connection did not differ substantially from those without this procedure. The type of superior cavopulmonary connection varied significantly by centre, but late outcomes were similar.

Surgical removal of pulmonary arteriovenous malformations subsequent to total cavopulmonary connection conversion long after a Björk procedure

Because the cavopulmonary shunt procedure is widely used for palliation of complex congenital heart diseases, pulmonary arteriovenous malformations (PAVMs) are relatively well-known complications. The reported patient was a 23-year-old woman who experienced PAVMs in the right lower lobe after a classical Glenn anastomosis and Björk procedure for tricuspid atresia. Her arterial oxygen saturation (SaO2) 14 years after the Björk procedure was ~80 %. She then underwent a total cavopulmonary connection (TCPC) conversion to reduce her PAVMs in the right lower lobe using the "hepatic factor." However, her situation remained unchanged, and she experienced severe systemic cyanosis (SaO2, 70 %) and dyspnea during physical exertion without hemoptysis due to increased blood flow to the PAVMs. Although interventional embolization was considered, it was impossible due to considerable dilation of the main PAVM. Thus, right lower lung lobectomy was performed. After surgery, the patient's SaO2 increased to 90 %. To the authors' knowledge, this is the first case report of a lung resection for residual PAVMs after TCPC conversion.

The intra/extracardiac conduit fenestrated fontan

The intra/extracardiac conduit technique for the Fontan procedure has important advantages relative to the extracardiac conduit. Fenestration is easily achieved and there is less risk of injury to the crista terminalis, so that the risk of late atrial arrhythmias may be reduced.

Comparison of shunt types in the Norwood procedure for single-ventricle lesions

BACKGROUND

The Norwood procedure with a modified Blalock-Taussig (MBT) shunt, the first palliative stage for single-ventricle lesions with systemic outflow obstruction, is associated with high mortality. The right ventricle-pulmonary artery (RVPA) shunt may improve coronary flow but requires a ventriculotomy. We compared the two shunts in infants with hypoplastic heart syndrome or related anomalies.

METHODS

Infants undergoing the Norwood procedure were randomly assigned to the MBT shunt (275 infants) or the RVPA shunt (274 infants) at 15 North American centers. The primary outcome was death or cardiac transplantation 12 months after randomization. Secondary outcomes included unintended cardiovascular interventions and right ventricular size and function at 14 months and transplantation-free survival until the last subject reached 14 months of age.

RESULTS

Transplantation-free survival 12 months after randomization was higher with the RVPA shunt than with the MBT shunt (74% vs. 64%, P=0.01). However, the RVPA shunt group had more unintended interventions (P=0.003) and complications (P=0.002). Right ventricular size and function at the age of 14 months and the rate of nonfatal serious adverse events at the age of 12 months were similar in the two groups. Data collected over a mean (+/-SD) follow-up period of 32+/-11 months showed a nonsignificant difference in transplantation-free survival between the two groups (P=0.06). On nonproportional-hazards analysis, the size of the treatment effect differed before and after 12 months (P=0.02).

CONCLUSIONS

In children undergoing the Norwood procedure, transplantation-free survival at 12 months was better with the RVPA shunt than with the MBT shunt. After 12 months, available data showed no significant difference in transplantation-free survival between the two groups. (ClinicalTrials.gov number, NCT00115934.)

[Surgical outcomes of arrhythmia surgery associated with total cavo-pulmonary connection conversion for failed Fontan]

BACKGROUND

The occurrence of late-onset supraventricular tachyarrhythmia is one of the major factors for Fontan failure. In 1999, we initiated the arrhythmia surgery with combined total cavo-pulmonary connection (TCPC) conversion for failed Fontan patients.

PATIENTS AND METHODS

From 1999 to 2008, a total of 7 patients (5 males) underwent arrhythmia surgery with TCPC conversion for supraventricular tachyarrhythmia causing Fontan failure. Median age at operation and duration from last Fontan operation were 20.3 year-old (14.5-38.9) and 15.6 years (9.9-26.2), respectively. Previous Fontan procedure was atrio-pulmonary connection (APC) in 4 patients, lateral tunnel in 2, and right atrial-ventricular anastomosis (Bjork procedure) in 1. Right side maze procedure was applied for intraatrial reentrant tachycardia (IART) and full maze for atrial fibrillation (Afib).

RESULTS

There ware no early death and 1 late death due to infectious endocarditis for median followup at 7.4 years (1.3-10.3). None of the patients showed recurrent or new onset IART or Afib, including the late expired case. Current New York Heart Association functional class was I in 4 patients and II in 2.

CONCLUSIONS

TCPC conversion with arrhythmic surgery was successfully performed failed Fontan patients. All patients were converted to sinus rhythm and have kept it until now.

Intracardiac covered stent for transcatheter completion of the total cavopulmonary connection: Anatomical, physiological and technical considerations

In the present review we discuss anatomical, physiological and technical aspects of the interventional transcatheter deployment of intracardiac covered stent for completion of the total cavopulmonary connection.

Hypoplastic left heart syndrome

Hypoplastic left heart syndrome is a rare congenital heart defect in which the left side of the heart is underdeveloped. Surgical management of hypoplastic left heart syndrome has changed the prognosis of the condition that was previously regarded as fatal. We discuss surgical strategies based on staged procedures, with the right ventricle supporting both systemic and pulmonary circulation. We also discuss other management options, such as neonatal transplantation and the recent innovation of hybrid techniques. Surgical techniques and the understanding of the pathophysiology of this condition have been at the forefront of neonatal cardiac surgery and intensive care. The management of the syndrome remains a challenge because affected children grow into adolescence and adulthood posing various new problems and demands.

[Staged total cavopulmonary connection for complex congenital heart diseases]

OBJECTIVE

To review the experience of staged total cavopulmonary connection (TCPC) in complex congenital heart diseases.

METHODS

From June 1998 to March 2008, 22 patients underwent staged TCPC for complex congenital heart diseases. Among them, 9 were univentricular and pulmonary artery valve stenosis; 3 were univentricular and pulmonary artery atresia; 1 was transposition of great arteries, crisscross heart and pulmonary artery valve stenosis; 1 was complete atrioventricular canal defects, left ventricular hypoplasia, pulmonary artery atresia and atrioventricular valvular regurgitation; 1 was complete atrioventricular canal defects, left ventricular hypoplasia, pulmonary artery valve stenosis and atrioventricular valvular regurgitation after Glenn procedure; 1 was mirror image dextrocardia, single ventricle, pulmonary artery atresia, major aortopulmonary collateral arteries (MAPCAs) and right pulmonary arteriovenous fistula after Glenn procedure; 4 were tricuspid atresia and pulmonary artery valve stenosis; 1 was tricuspid atresia and pulmonary atresia; 1 was mirror image dextrocardia, double-outlet of right ventricle, left ventricular hypoplasia, pulmonary artery valve stenosis, tricuspid incompetence, and MAPCAs. Among them, 5 patients received systemic-to-pulmonary artery shunt, bidirectional Glenn procedure and TCPC. Seventeen patients received bidirectional Glenn procedure, the mean age was (5.9+/-4.4) years old. Pulmonary artery pressure pre-Glenn procedure was 17 to 20 mm Hg (1 mm Hg=0.133 kPa). Atrioventricular valve incompetence in 3 patients. Nakata index was less than 200 mm2/m2 in 4 patients before the first stage operation. The age of TCPC procedure was (9.6+/-4.9) years old, the interval time was (3.7+/-1.2) years.

RESULTS

There was one in-hospital death, the mortality was 4.5%. The patient with univentricular and pulmonary atresia, received systemic-to-pulmonary artery shunt, bidirectional Glenn procedure and TCPC and died of pneumorrhagia. Other patients were recovered well, postoperative central venous pressure was 12 to 18 mm Hg, percutaneous oxygen saturation was 90% to 96%. The cardiac function were in NYHA class I to II.

CONCLUSIONS

The staged TCPC was a good procedure in high-risk Fontan candidates. The results were satisfactory for those patients. This staged strategy may extend the operative indications for the Fontan procedure.

[Results of bidirectional cavapulmonary shunt operation without cardiopulmonary bypass in children with complicated congenital heart defects during the first year of life]

The authors present results of bidirectional cavapulmonary shunt operation without cardiopulmonary bypass for the treatment of complicated congenital heart defects. Temporary blood shunting during surgical intervention enables cavapulmonary anastomosis to be created without making resort to artificial circulation (AC) and limitation on the time of superior vena cava occlusion. The proposed method is free from additional risks and excludes negative effects of AC. It allows for conversion to AC as appropriate at any time during surgery in the "bypass stand-by" regime.

Bidirectional Glenn and antegrade pulmonary blood flow: temporary or definitive palliation?

BACKGROUND

We sought to investigate the role of the bidirectional Glenn with antegrade pulmonary blood flow in the surgical history of children with univentricular hearts.

METHODS

A series of 246 patients, from three joint institutions, having univentricular heart with restricted but not critical pulmonary blood flow received a bidirectional cavopulmonary shunt with additional forward pulmonary blood flow. All patients have been studied according to their progression, or not, to Fontan operation. Two hundred and eight (84.5%) patients underwent bidirectional cavopulmonary anastomosis as primary palliation. Twenty patients (8.1%) with previous pulmonary artery banding were also enrolled in the study. Patients who had received additional pulmonary blood flow through a previous systemic to pulmonary artery shunt for the critical pulmonary blood flow were excluded.

RESULTS

No in-hospital death occurred. Follow-up was complete at 100%. Mean follow-up was 4.2 +/- 2.8 years (range, 6 months to 7 years). During the observational period 73 (29.7%) patients, considered optimal candidates, underwent Fontan completion for increasing cyanosis and (or) hematocrit and (or) fatigue with exertion. Three patients expired after total cavopulmonary connection (3 of 73; 4.1% mortality rate). The remaining 173 (70.3%) patients are alive with initial palliation. All patients were still well palliated with an arterial oxygen saturation at rest about 90%.

CONCLUSIONS

According to our experience and results, bidirectional Glenn with antegrade pulmonary blood flow may be an excellent temporary palliation prior to a Fontan operation, which can be performed at the onset of symptoms. Bidirectional Glenn may also be the best possible palliation for a suboptimal candidate for Fontan.

Caval blood flow during supine exercise in normal and Fontan patients

BACKGROUND

Extracardiac total cavo-pulmonary connection (TCPC) bypasses the right atrium and has in theory better hemodynamics than intraatrial TCPC repair. Both are thought to have inferior hemodynamics compared with a normal circulation. Direct comparison of flow rates at rest and during exercise with magnetic resonance imaging technique have not been performed.

METHODS

The study comprised 20 children. Six children (median age, 9.3 years; interquartile range, 2.2) had undergone extracardiac TCPC. Eight children (median age, 8.9 years; interquartile range, 5.0) had an intraatrial TCPC, and 6 children (median age, 10.3 years; interquartile range, 2.6) were healthy control subjects. Blood flows in the aorta, inferior vena cava, and superior vena cava were measured at rest and during two levels of submaximal supine bicycle exercise (0.5 W/kg and 1.0 W/kg) using a magnetic resonance imaging scanner mounted with a bicycle.

RESULTS

Heart rate, respiratory rate, inspiratory fraction, and blood flow rates in the aorta and inferior vena cava increased equally in all three groups. If patients were grouped together, flow rates were significantly lower, and the inspiratory flow fraction in the inferior vena cava was significantly higher, than in control subjects. Retrograde flows were observed in all three groups at rest but tapered off with exercise.

CONCLUSIONS

At submaximal levels of lower limb exercise, patients with extracardiac as well as intraatrial TCPC showed a similar increase in respiration, heart rate, and aortic and caval flow rates as healthy control subjects. This is in accordance with the observation that many patients with TCPC perform well during daily life activities.

Nonfenestrated extracardiac total cavopulmonary connection in 132 consecutive patients

BACKGROUND

The study was conducted to assess the need for fenestration for completion of a total cavopulmonary connection (TCPC) with the most recent modification of an extracardiac conduit.

METHODS

The extracardiac approach was introduced to our institution in January 1999. Between June 2000 and June 2006, 132 consecutive patients were treated without a fenestration. At the time of TCPC, the median age was 31 months (range, 16 251), with 93 patients (70%) being younger than 48 months. Median patient weight was 12.5 kg (range, 9 to 66 kg). A previous partial cavopulmonary connection (PCPC) was accomplished in 117 patients (88.6%), without additional pulmonary blood flow.

RESULTS

Thirty-day-mortality was 1.5%. Median time to extubation was 14 hours (range, 3 hours to 126 days). Initial pulmonary artery pressure value was 16.5 +/- 2.2 mm Hg, and 13.1 +/- 1.8 after extubation. Median drainage requirement was 4 days (range, 1 to 45), and median duration of hospitalization was 20 days (range, 5 to 128). Thirty-one (24%) required repeat drainage insertion. No subsequent fenestration was performed, and at hospital discharge no significant repeat effusions were observed. Multiple covariate logistic regression revealed longer time interval from PCPC to extracardiac TCPC (p = 0.006) as a significant predictor of pleural drainage lasting longer than 4 days, and older age at the time of extracardiac TCPC (p = 0.040) as a risk factor for hospitalization more than 20 days. Higher pulmonary artery pressure 3 hours postoperatively was a significant predictor for both outcome variables in the multivariate model (p = 0.013, p = 0.001).

CONCLUSIONS

In general, an extracardiac TCPC can be performed without fenestration. Early staging of patients with functional single ventricle physiology may be one of the keys for these findings.

Trendelenburg Position, Simulated Valsalva Maneuver, and Liver Compression Do Not Alter the Size of the Right Internal Jugular Vein in Patients with a Bidirectional Glenn Shunt

BACKGROUND

Ultrasound is increasingly used to facilitate right internal jugular vein (RIJV) cannulation in children. In children without cardiac disease, position changes and enhancement maneuvers increase RIJV cross-sectional area (CSA) and further facilitate cannulation. We investigated the effect of these maneuvers on RIJV CSA in children with a bidirectional Glenn (BDG) shunt presenting for a Fontan procedure.

METHODS

The CSA (cm(2)) of the RIJV in 21 children with a BDG shunt presenting for a Fontan procedure was assessed by ultrasonic planimetry (SonoSite). Two positions, supine (S) and 15 degrees Trendelenburg (T); and two enhancements maneuvers, manual liver compression (L) and a simulated Valsalva maneuver (V) were utilized in combination. Eight separate measurements (S, S + L, S + V, S + L + V, T, T + L, T + V, T + L + V) were made in each patient. Data were analyzed using one-way analysis of variance with repeated measures and with Tukey post hoc pairwise comparison analysis.

RESULTS

No significant change in the RIJV CSA or % change in CSA from baseline (S) was observed.

CONCLUSIONS

Position changes and enhancement maneuvers are unlikely to facilitate RIJV cannulation in BDG shunt patients presenting for Fontan procedure because these interventions do not increase RIJV CSA.

Progress in the CFD modeling of flow instabilities in anatomical total cavopulmonary connections

Intrinsic flow instability has recently been reported in the blood flow pathways of the surgically created total-cavopulmonary connection. Besides its contribution to the hydrodynamic power loss and hepatic blood mixing, this flow unsteadiness causes enormous challenges in its computational fluid dynamics (CFD) modeling. This paper investigates the applicability of hybrid unstructured meshing and solver options of a commercially available CFD package (FLUENT, ANSYS Inc., NH) to model such complex flows. Two patient-specific anatomies with radically different transient flow dynamics are studied both numerically and experimentally (via unsteady particle image velocimetry and flow visualization). A new unstructured hybrid mesh layout consisting of an internal core of hexahedral elements surrounded by transition layers of tetrahedral elements is employed to mesh the flow domain. The numerical simulations are carried out using the parallelized second-order accurate upwind scheme of FLUENT. The numerical validation is conducted in two stages: first, by comparing the overall flow structures and velocity magnitudes of the numerical and experimental flow fields, and then by comparing the spectral content at different points in the connection. The numerical approach showed good quantitative agreement with experiment, and total simulation time was well within a clinically relevant time-scale of our surgical planning application. It also further establishes the ability to conduct accurate numerical simulations using hybrid unstructured meshes, a format that is attractive if one ever wants to pursue automated flow analysis in a large number of complex (patient-specific) geometries.

Anesthetic management of bidirectional cavopulmonary shunt in a patient with pulmonary atresia with intact ventricular septum associated with sinusoidal communications

Pulmonary atresia with intact ventricular septum (PAIVS) is sometimes associated with coronary artery anomalies, including right ventricle (RV)-to-coronary artery fistulas (sinusoidal communications), coronary artery stenoses, and coronary artery occlusions. In some cases, the coronary circulation depends entirely or partly on the desaturated systemic venous blood supply from the RV. Under these circumstances, decompression of the RV can result in fatal myocardial ischemia. A 6-month-old boy, diagnosed with PAIVS associated with sinusoidal communications, underwent a bidirectional cavopulmonary shunt procedure under venoarterial cardiopulmonary bypass (CPB). During CPB, to prevent RV decompression, we maintained right atrial pressure above 5 mmHg and used a pump perfusion rate of 30%-40% of the calculated value based on body surface area. Although electrocardiography showed slight ST depression and bradycardia, myocardial contractility after weaning from CPB was adequate to maintain the circulation with the administration of dobutamine and atrial pacing. In patients with PAIVS and RV-dependent coronary circulation, it is important to maintain coronary artery perfusion throughout the period of anesthesia.

Effects of Exercise and Respiration on Hemodynamic Efficiency in CFD Simulations of the Total Cavopulmonary Connection

Congenital heart defects with a single functional ventricle, such as hypoplastic left heart syndrome and tricuspid atresia, require a staged surgical approach to separate the systemic and pulmonary circulations. Ultimately, the venous or pulmonary side of the heart is bypassed by directly connecting the vena cava to the pulmonary arteries with a modified t-shaped junction. The Fontan procedure (total cavopulmonary connection, TCPC) completes this process of separation. To date, computational fluid dynamics (CFD) simulations in this low pressure, passive flow, intrathoracic system have neglected the presumed important effects of respiration on physiology and higher "stress" states such as with exercise have never been considered. We hypothesize that incorporating effects of respiration and exercise would provide more realistic estimates of TCPC performance. Time-dependent, 3D blood flow simulations are performed by a custom finite element solver for two patient-specific Fontan models with a novel respiration model, developed to generate physiologic time-varying flow conditions. Blood flow features, pressure, and energy efficiency are analyzed at rest and with increasing flow rates to simulate exercise conditions. The simulations produce realistic pressure and flow data, comparable to that measured by catheterization and echocardiography, and demonstrate substantial increases in energy dissipation (i.e. decreased performance) with exercise and respiration due to increasing intensity of small scale vortices in the flow. As would be expected, these changes are highly dependent on patient-specific anatomy and Fontan geometry. We propose that respiration and exercise should be incorporated into TCPC CFD simulations to provide increasingly realistic evaluations of TCPC performance.

Refined anaesthesia for implantation of engineered experimental aortic valves in the pulmonary artery using a right heart bypass in sheep

The feasibility of an anaesthetic protocol developed for surgery during right heart bypass in sheep is reported. Seven female Suffolk sheep, weighing 25-35 kg, were selected for the study. Premedication consisted of midazolam and methadone (both 0.1 mg kg(-1) intravenously). Anaesthesia was induced with propofol (2-4 mg kg(-1)) and maintained with isoflurane in oxygen and continuous rate infusions of propofol (5-7 mg kg(-1 )h(-1)) and fentanyl (5 microg kg(-1) bolus, 5 microg kg(-1) h(-1)). Cisatracurium (0.2 mg kg(-1)) provided muscle relaxation. A standard roller pump was used for the extracorporeal circulation. Drugs administered to maintain blood pressure and heart rate within acceptable levels included phenylephrine (3-4 microg kg(-1)), ephedrine (0.1-0.2 mg kg(-1)), nitroglycerine (50-150 microg kg(-1) h(-1)) and metoprolol succinate (30-80 microg kg(-1)). Electrolytes were infused as needed. Postoperative analgesia was provided by an intercostal block (15 mL 0.5% bupivacaine + epinephrine), carprofen (4 mg kg(-1)) and an opioid (methadone 0.1 mg kg(-1) or buprenorphine 0.01 mg kg(-1)). One sheep became hypoxic during the bypass (PaO(2) 47.7 mmHg). Irregularities of the electrocardiogram were observed during manipulation of the heart in all animals. During the initial phase of the bypass, blood pressure decreased in all sheep, accompanied by dilatation of the heart and large intrathoracic veins in five sheep. With appropriate treatment, blood pressure was restored and easily maintained until the end of the bypass. Weaning from the bypass, using an infusion of nitrates, was smooth. One sheep required a blood transfusion because of severe blood loss and another sheep died postoperatively from respiratory complications. Minor irregularities of the electrocardiogram observed during manipulation of the heart were not life threatening and required no treatment. Decreases in blood pressure at the beginning of the bypass can be expected and require treatment. Nitrates are useful in avoiding volume overload during weaning. The anaesthetic protocol is acceptable for surgery under right heart bypass in sheep.

Incorporation of the hepatic veins into the cavopulmonary circulation in patients with heterotaxy and pulmonary arteriovenous malformations after a Kawashima procedure

BACKGROUND

In patients with polysplenia syndrome and azygous continuation of an interrupted inferior vena cava (IVC), pulmonary arteriovenous malformations (PAVMs) are relatively common after bidirectional cavopulmonary anastomosis (BCPA, Kawashima procedure). Resolution of PAVMs after hepatic vein (HV) inclusion into the cavopulmonary circulation has been reported, but there has been no systematic investigation of the effects of this therapy in a population of more than 3 patients.

METHODS

We studied 16 patients with heterotaxy, univentricular congenital heart disease, and azygous continuation of the IVC who underwent incorporation of the HV into the cavopulmonary circuit for treatment of significant PAVMs after a Kawashima procedure.

RESULTS

The median preoperative systemic arterial oxygen saturation (SsaO2) was 76% (65%-85%), compared with 89% (85% to 92%) early after BCPA. Among 15 early survivors, the median early postoperative SsaO2 was 76% (56%-85%). In 11 of the 15 survivors, SsaO2 rose to 90% or greater within a year and remained at 93% or greater at follow-up of 2.8 to 10 years. Four patients had persistent hypoxemia and residual PAVMs at follow-up catheterization 1.5 to 8 years postoperatively; these patients had the most severe hypoxemia prior to HV inclusion, and in 2 the residual PAVMs were unilateral, with HV flow streaming to the contralateral lung, in which PAVMs had resolved.

CONCLUSIONS

Hypoxemia resolved after cavopulmonary incorporation of the HV in the majority of our patients with PAVMs after the Kawashima operation, presumably due to a combination of PAVM resolution and elimination of hepatic venoatrial right-to-left shunting. These findings support the theory that development of PAVMs is facilitated by exclusion of HV effluent from the pulmonary circulation.

Analytical Identification of Ideal Pulmonary-Systemic Flow Balance in Patients With Bidirectional Cavopulmonary Shunt and Univentricular Circulation

Background— In the present study, we extended previous mathematical modeling work on patients with bidirectional cavopulmonary (“bidirectional Glenn”) anastomosis to assess the potential utility of several descriptors of oxygen status. We set out to determine which of these descriptors best represents the overall tissue oxygenation. We also introduce a new descriptor, S o 2 min, defined as the lower of the superior and inferior vena cava oxygen saturations.

Methods and Results— The application of differential calculus to a model of oxygen physiology of patients with bidirectional Glenn allowed simultaneous assessment of all possible distributions of blood flow and metabolic rate between upper and lower body, across all cardiac outputs, total metabolic rates, and oxygen-carrying capacities. When total cardiac output is fixed, although it may intuitively seem best to distribute flow to maximize oxygen delivery (total, upper body, or lower body), we found that for each variable, there are situations in which its maximization seriously deprives flow to the upper or lower circulation. In contrast, maximizing S o 2 min always gives physiologically sensible results. If the majority of metabolism is in the upper body (typical of infancy), then oxygenation is optimized when flow distribution matches metabolic distribution. In contrast, if the majority of metabolism is in the lower body (typical of older children and during exercise), oxygenation is optimal when flows are equal.

Conclusions— In patients with bidirectional cavopulmonary anastomosis, because there is a tradeoff between flow distribution and saturation, it is unwise to concentrate on maximizing oxygen delivery. Maximizing systemic venous saturations (especially S o 2 min) is conceptually different and physiologically preferable for tissue oxygenation.

Advantages of temporary venoatrial shunt using centrifugal pump during bidirectional cavopulmonary shunt

Single-ventricle palliation without the use of cardiopulmonary bypass carries advantages that reduce systemic edema and inflammatory responses; however, simple clamping of the superior vena cava (SVC) without a temporary shunt leads to increase in cerebral venous pressure and subsequent decrease in cerebral blood flow during bidirectional cavopulmonary shunt (BCPS). We report our experience of BCPS, using a centrifugal pump-assisted temporary shunt. The criteria included an unrestrictive interatrial communication, the absence of atrioventricular valve regurgitation, and the existence of an antegrade pulmonary blood flow. From August 2000, 14 children with single-ventricle physiology met the criteria. The mean age was 1.0 +/- 0.9 years, and the mean weight was 8.4 +/- 2.6 kg. A temporary shunt was established between the SVC and the right atrium with right-angle cannulae, which were connected to a centrifugal pump to accelerate the blood flow from the SVC to the right atrium. All patients tolerated the procedure. Mean central venous pressure was 17 +/- 4 mm Hg, and transcutaneous oxygen saturation was maintained at 77 +/- 8% during anastomosis. No patients required blood transfusion. There were no postoperative neurological complications. The centrifugal pump-assisted temporary shunt offered safer and more effective circulatory support than other shunt systems, with excellent venous drainage in pediatric patients undergoing BCPS.

Temporary Right Heart Support With Percutaneous Jugular Access

PURPOSE

Temporary right heart bypass has shown to improve hemodynamic stability and safety in beating heart revascularization. We sought to evaluate feasibility and safety of a right ventricular assist device percutaneously implanted in the right jugular vein.

DESCRIPTION

The A-Med jugular coaxial cannula (A-Med Systems Inc, West Sacramento, CA) is designed for percutaneous implantation. Blood from the right heart is drained through the outer tube of this two-cannula device to a microcentrifugal pump and returned into the pulmonary artery through the inner tube.

EVALUATION

In 10 patients scheduled for elective coronary bypass grafting without cardiopulmonary bypass, a total of 27 coronary anastomoses were performed with right heart support. Arterial pressure was significantly higher with right heart support when the heart was dislocated to access posterior and posterolateral anastomosis sites. Implantation through the right internal jugular vein was feasible without complications in all patients and facilitated the procedure.

CONCLUSIONS

This initial study suggests safety and feasibility of temporary right heart support using percutaneous jugular access for posterior and posterolateral coronary bypass grafting.

Can we do without routine fenestration in extracardiac total cavopulmonary connections? Report on 84 consecutive patients

Fenestration is still widely used in right heart bypass operations. Our study was conducted to assess its need in the most recent modification, the completion of a total cavopulmonary connection with an extracardiac tube. The extracardiac approach was introduced at our institution in January, 1999. Since June of 2000, no patient had a fenestration. If more than 1 risk factor amongst ventricular function being more than moderately impaired, atrioventricular valvar regurgitation more than moderate, mean pulmonary arterial pressure more than 15 millimetres of mercury, mean atrial pressure higher than 12 millimetres of mercury, pulmonary arterial distortion, or other than sinus rhythm was present preoperatively, the patient was considered a "high risk" candidate. Postoperatively elevated pulmonary arterial pressure higher than 16 millimetres of mercury, prolonged effusions and requirement for drainage longer than 7 days, and death were considered endpoints in the statistical analysis. Our study group included 84 patients who underwent surgery up to August, 2004. A previous bidirectional cavopulmonary anastomosis had been accomplished in 73 patients at a mean age of 27.01 plus or minus 32.60 months, with a median of 11.5 months, without creating an additional source of flow of blood to the lungs. At the time of the total cavopulmonary connection, the mean age was 66.4 plus or minus 60.1 months, with a median of 37.1 months, and a range from 17.3 to 251.2 months, with 50 patients being younger than 48 months. We deemed 16 patients to be at "high risk". These patients were older at the time of bidirectional cavopulmonary anstomosis (p smaller than 0.016), at the time of completion (p smaller than 0.019), and also differed in size at time of completion (p smaller than 0.020). They required a longer time on cardiopulmonary bypass (p smaller than 0.015), and reached higher early postoperative pulmonary arterial pressures after completion (p smaller than 0.025). There were no differences between groups of patients having up to 1 or more risk factors in regard to need for intubation (p smaller than 0.511), pulmonary arterial pressures after extubation (p smaller than 0.817), and duration of chest drainage (p smaller than 0.650). Three patients died, one in the group deemed at high risk. There was no death in the last 38 patients. We conclude that a total cavopulmonary connection with an extracardiac tube can be performed without fenestration, even if the patients are deemed to be at increased risk. Early staging of patients with functionally univentricular physiology might be one of the keys for these findings.

Conversion of atriopulmonary Fontan to extracardiac total cavopulmonary connection improves cardiopulmonary function

BACKGROUND

Experimental studies showed that extracardiac total cavopulmonary connection provides superior hemodynamics than atriopulmonary Fontan.

METHODS

We prospectively assessed the impact of conversion of atriopulmonary Fontan to extracardiac total cavopulmonary connection on exercise capacity and cardiac function in 6 consecutive patients.

RESULTS

Six months after conversion to extracardiac total cavopulmonary connection, we observed an increase in peak oxygen uptake in all patients (p=0.01;+17%). This improvement was associated to an increase of peak O(2) pulse (p=0.01;+16%), but no change in peak heart rate, arterial oxygen saturation at peak exercise, and pulmonary function. Ventricular ejection fraction did not change significantly after surgery. Conversion was associated with an improvement in heart failure symptoms as assessed by the New York Heart Association classification. Patients who had undergone additional anti-arrhythmia surgery for atrial fibrillation had no recurrence of arrhythmia at follow-up.

CONCLUSION

Data indicate that conversion to extracardiac total cavopulmonary connection is associated with an improvement of cardiopulmonary function and heart failure symptoms. Improved exercise capacity is due to an increase in O(2) pulse and may reflect an improved cardiac stroke volume after the operation.

A Gore-Tex 'new-innominate' vein: a surgical option for complicated bilateral cavopulmonary shunts

A bilateral bidirectional cavopulmonary shunt was performed in a cyanotic 14-month-old girl who had tricuspid and pulmonary valve atresia, with right pulmonary artery (RPA) hypoplasia (3 mm), bilateral superior vena cavae and a ductus arteriosus-dependent pulmonary blood flow. Because of 62% postoperative arterial oxygen saturation and a right superior vena cava (RSVC) pressure of 30 mmHg, a 5 mm Gore-Tex tube was interposed to connect the two superior venae cavae. The creation of a 'new-innominate' vein allowed decompression of the right superior vena cava and an increase in arterial oxygen saturation to 86%.

Cavo-pulmonary shunt for left ventricular outflow tract obstruction after senning

We report a case of Senning procedure in a 32-month-old girl with transposition of the great arteries and dynamic left ventricular outflow tract obstruction (LVOTO). After discontinuation of cardio-pulmonary bypass, the persisting, worsened LVOTO caused hemodynamical instability. A cavo-pulmonary shunt (CPS) was performed, with considerable subsequent improvement. We consider the use of CPS as a valuable option in patients with persisting, significant dynamic LVOTO after atrial switch.

Three-dimensional velocity field reconstruction

The problem of inter-slice magnetic resonance (MR) image reconstruction is encountered often in medical imaging applications, in such scenarios, there is a need to approximate information not captured in contiguously acquired MR images due to hardware sampling limitations. In the context of velocity field reconstruction, these data are required for visualization and computational analyses of flow fields to be effective. To provide more complete velocity information, a method has been developed for the reconstruction of flow fields based on adaptive control grid interpolation (ACGI). In this study, data for reconstruction were acquired via MRJ from in vitro models of surgically corrected pediatric cardiac vasculatures. Reconstructed velocity fields showed strong qualitative agreement with those obtained via other acquisition techniques. Quantitatively reconstruction was shown to produce data of comparable quality to accepted velocity data acquisition methods. Results indicate that ACGI-based velocity field reconstruction is capable of producing information suitable for a variety of applications demanding three-dimensional in vivo velocity data.

A novel technique for off pump bidirectional Glenn shunt--safety issues--a case report

A new technique to decompress the superior vena cava (SVC) during off pump bi-directional Glenn [BDG] shunts is described. Cerebral protection maneuvers and the safety concerns of the technique are addressed.

Surgical management of an extracardiac total cavopulmonary connection in heterotaxy syndrome with isolated hepatic drainage

The extracardiac modification for completion of a cavopulmonary connection has added a further option for direction of inferior vena cava and/or hepatic venous drainage to the pulmonary arteries. The authors describe a technique of isolating a hepatic vein and connecting it to the inferior caval vein in a side-by-side fashion prior to anastomosing it to the tubegraft in a patient with heterotaxy syndrome.

Multiscale modeling of the cardiovascular system: application to the study of pulmonary and coronary perfusions in the univentricular circulation

The objective of this study is to compare the coronary and pulmonary blood flow dynamics resulting from two configurations of systemic-to-pulmonary artery shunts currently utilized during the Norwood procedure: the central (CS) and modified Blalock Taussig (MBTS) shunts. A lumped parameter model of the neonatal cardiovascular circulation and detailed 3-D models of the shunt based on the finite volume method were constructed. Shunt sizes of 3, 3.5 and 4 mm were considered. A multiscale approach was adopted to prescribe appropriate and realistic boundary conditions for the 3-D models of the Norwood circulation. Results showed that the average shunt flow rate is higher for the CS option than for the MBTS and that pulmonary flow increases with shunt size for both options. Cardiac output is higher for the CS option for all shunt sizes. Flow distribution between the left and the right pulmonary arteries is not completely balanced, although for the CS option the discrepancy is low (50-51% of the pulmonary flow to the right lung) while for the MBTS it is more pronounced with larger shunt sizes (51-54% to the left lung). The CS option favors perfusion to the right lung while the MBTS favors the left. In the CS option, a smaller percentage of aortic flow is distributed to the coronary circulation, while that percentage rises for the MBTS. These findings may have important implications for coronary blood flow and ventricular function.

Single-Step Stereolithography of Complex Anatomical Models for Optical Flow Measurements

Transparent stereolithographic rapid prototyping (RP) technology has already demonstrated in literature to be a practical model construction tool for optical flow measurements such as digital particle image velocimetry (DPIV), laser doppler velocimetry (LDV), and flow visualization. Here, we employ recently available transparent RP resins and eliminate time-consuming casting and chemical curing steps from the traditional approach. This note details our methodology with relevant material properties and highlights its advantages. Stereolithographic model printing with our procedure is now a direct single-step process, enabling faster geometric replication of complex computational fluid dynamics (CFD) models for exact experimental validation studies. This methodology is specifically applied to the in vitro flow modeling of patient-specific total cavopulmonary connection (TCPC) morphologies. The effect of RP machining grooves, surface quality, and hydrodynamic performance measurements as compared with the smooth glass models are also quantified.

Clinical advantages of total cavopulmonary anastomosis without cardiopulmonary bypass

OBJECTIVE

To evaluate surgical methods and results of extracardiac conduit total cavopulmonary anastomosis (EC-TCPA) without cardiopulmonary bypass (CPB).

METHODS

From May 2000 to April 2003, 11 patients with functional univentricle underwent off-pump EC-TCPA (no-CPB group). Their postoperative outcome was retrospectively compared with a 17-patient group who underwent EC-TCPA with cardiopulmonary bypass (CPB group) over a concurrent time period.

RESULTS

There was 1 operative death in no-CPB group and 2 in CPB group; early postoperative hemodynamics appeared to significantly improve in no-CPB group. Blood and platelet transfusions decreased and blood plasma transfusion significantly lowered in no-CPB group compared with CPB group (P = 0.036). Postoperative courses of patients in no-CPB group were smooth and event free, and extubation time was substantially short Intensive cares unit stay (P = 0.04) and hospital stay (P = 0.02) postoperation were significantly shorter, hospital costs were significantly reduced (P = 0.004) in no-CPB group compared with CPB group.

CONCLUSIONS

EC-TCPA without use of CPB is not a difficult procedure; the procedure results in improvement in postoperative hemodynamics, and decreased use of blood and blood products. It is a more efficient operation with more short recovery time and reduced hospital stay.

The Effect of Incorporating Vessel Compliance in a Computational Model of Blood Flow in a Total Cavopulmonary Connection (TCPC) with Caval Centerline Offset

Background—The total cavopulmonary connection (TCPC), a palliative correction for congenital defects of the right heart, is based on the corrective technique developed by Fontan and Baudet. Research into the TCPC has primarily focused on reducing power loss through the connection as a means to improve patient longevity and quality of life. The goal of our study is to investigate the efficacy of including a caval offset on the hemodynamics and, ultimately, power loss of a connection. As well, we will quantify the effect of vessel wall compliance on these factors and, in addition, the distribution of hepatic blood to the lungs. Methods—We employed a computational fluid dynamic model of blood flow in the TCPC that includes both the non-Newtonian shear thinning characteristics of blood and the nonlinear compliance of vessel tissue. Results—Power loss in the rigid-walled simulations decayed exponentially as caval offset increased. The compliant-walled results, however, showed that after an initial substantial decrease in power loss for offsets up to half the caval diameter, power loss increased slightly again. We also found only minimal mixing in both simulations of all offset models. Conclusions—The increase in power loss beyond an offset of half the caval diameter was due to an increase in the kinetic contribution. Reduced caval flow mixing, on the other hand, was due to the formation of a pressure head in the offset region which acts as a barrier to flow.