Ring-Enforced Right Ventricle-to-Pulmonary Artery Conduit in Norwood Stage I Reduces Proximal Conduit Stenosis

Norwood Operation with Right Ventricular-Pulmonary Artery Shunt Versus Comprehensive Stage II After Bilateral Pulmonary Artery Banding Palliation

As a strategy for the primary Norwood operation, the right ventricular-pulmonary artery shunt is associated with satisfactory early outcome. However, use of this shunt after bilateral pulmonary artery banding remains controversial. This study compared the operative outcomes and late hemodynamics in patients who underwent the Norwood operation, preceded by bilateral pulmonary artery banding, with a right ventricular-pulmonary artery shunt or with bidirectional Glenn anastomosis (comprehensive stage II strategy). We retrospectively reviewed 38 patients who underwent the Norwood operation preceded by bilateral pulmonary artery banding between 2004 and 2017. Of these, 17 underwent the Norwood operation with a right ventricular-pulmonary artery shunt (Group S), whereas 21 underwent the comprehensive stage II strategy (Group G). 5 years after the Norwood operation, 10 (60%) and 17 (81%) patients in Group S and Group G, respectively, underwent the Fontan procedure. Group S showed significantly lower pressure in the superior vena cava after bidirectional Glenn anastomosis than Group G (13 ± 2 mmHg vs. 18 ± 3 mmHg; p < 0.01), but pressures were similar after the Fontan procedure. The right ventricular end-diastolic volume at 1 year post-Fontan procedure was significantly higher in Group S than in Group G (142 ± 41% vs. 91 ± 28%; p < 0.01). In terms of early outcomes, the Norwood operation with a right ventricular-pulmonary artery shunt enabled low pressure in the superior vena cava, but in the long term, this shunt adversely influenced the right ventricular volume.

Longitudinal analysis of systemic ventricular function and atrioventricular valve function after the Norwood procedure

OBJECTIVES

To evaluate longitudinal systemic ventricular function and atrioventricular valve regurgitation in patients after the neonatal Norwood procedure.

METHODS

Serial postoperative echocardiographic images before Fontan completion were assessed in neonates who underwent the Norwood procedure between 2001 and 2020. Ventricular function and atrioventricular valve regurgitation were compared between patients with modified Blalock-Taussig shunt and right ventricle to pulmonary artery conduit.

RESULTS

A total of 335 patients were identified including 273 hypoplastic left heart syndrome and 62 of its variants. Median age at Norwood was 8 (7-12) days. Modified Blalock-Taussig shunt was performed in 171 patients and the right ventricle to pulmonary artery conduit in 164 patients. Longitudinal ventricular function and atrioventricular valve regurgitation were evaluated using a total of 4352 echocardiograms. After the Norwood procedure, ventricular function was initially worse (1-30 days) but thereafter better (30 days to stage II) in the right ventricle to pulmonary artery conduit group (P < 0.001). After stage II, the ventricular function was inferior in the right ventricle to the pulmonary artery conduit group (P < 0.001). Atrioventricular valve regurgitation between the Norwood procedure and stage II was more frequent in the modified Blalock-Taussig shunt group (P < 0.001). After stage II, there was no significant difference in atrioventricular valve regurgitation between the groups (P = 0.171).

CONCLUSIONS

The effect of shunt type on haemodynamics after the Norwood procedure seems to vary according to the stage of palliation. After the Norwood, the modified Blalock-Taussig shunt is associated with poorer ventricular function and worse atrioventricular valve regurgitation compared to right ventricle to pulmonary artery conduit. Whereas, after stage II, modified Blalock-Taussig shunt is associated with better ventricular function and comparable atrioventricular valve regurgitation, compared to the right ventricle to pulmonary artery conduit.

Journey Toward Improved Long-Term Outcomes After Norwood-Sano Procedure: Focus on the Aortic Arch Reconstruction

The disadvantage of right ventricle-to-pulmonary artery (RV-PA) shunt is the need for more unplanned interventions to address stenosis in the shunt or branch pulmonary arteries, as compared to the modified Blalock-Taussig shunt group. Ring-enforced RV-PA PTFE conduit and dunk technique minimized these complications and right ventricle (RV) damage. Aortic arch obstruction increases afterload and leads to ventricular dysfunction and tricuspid regurgitation; therefore, most surgeons prefer to use homograft, autologous pericardium, or bovine pericardium to reconstruct the neoaorta. Artificial materials decrease the elastic properties, increase wall stiffness, and decrease the distensibility of the aorta; and as a result, RV function gradually deteriorates. This inelastic reconstructed aorta may be one of the reasons why long-term outcomes after the Fontan procedure are worse in hypoplastic left heart syndrome (HLHS) patients, in comparison to non-HLHS. Reconstruction of the neoaorta without any patch materials, or at least techniques that largely minimize the use of non-autologous materials, will offer a further refinement of our ability to optimize ventriculoarterial coupling and thereby long-term RV function.

Tricuspid annuloplasty ring for external support of right ventricle-to-pulmonary artery conduit

We describe the use of a rigid tricuspid annuloplasty ring as an external support to avoid compression of a right ventricle-to-pulmonary artery conduit.

Influence of Shunt Type on Survival and Right Heart Function after the Norwood Procedure for Aortic Atresia

The study objective was to compare the results after Norwood procedure between modified Blalock-Taussig shunt (MBTS) and right ventricle-to-pulmonary artery conduit (RVPAC) according to Sano in patients with hypoplastic left heart syndrome (HLHS) and aortic atresia (AA). A total of 146 neonates with HLHS and AA who underwent the Norwood procedure at our institution between 2001 and 2020 were divided into 2 groups according to shunt type (MBTS or RVPAC). Survival after the Norwood procedure was compared between the groups. Longitudinal right ventricular and tricuspid valve function in each group were evaluated using cubic splines method. RVPAC was performed in 103 patients and MBTS in 43 according to surgeon preference. There were no differences in the 30-day mortality rates (16.5% vs 16.3%, P  = 0.973). Survival at 0.5, 1 and 3 years was 79.6%, 74.6%, and 68.9% in RVPAC and 66.8%, 64.3%, and 58.5% in MBTS (P  =  0.293). Among 23 patients undergoing tricuspid valve procedure, different mechanisms of tricuspid regurgitation were observed between the groups. Longitudinal analysis revealed greater prevalence of late right ventricular dysfunction in RVPAC patients. In 77 patients who completed Fontan procedure, the postoperative N-terminal pro B-type natriuretic peptide value was significantly higher in RVPAC vs MBTS (554 vs 276 ng/L, P  =  0.007). No survival advantage of RVPAC over MBTS was observed in neonates with HLHS and AA undergoing the Norwood procedure. Longitudinal analysis demonstrated a greater prevalence of right ventricular dysfunction and higher N-terminal pro B-type natriuretic peptide values during late follow-up in patients with RVPAC.

Preoperative risk factors influencing inter-stage mortality after the Norwood procedure

OBJECTIVES

With improvements in early survival after the stage I palliation (S1P) Norwood procedure for hypoplastic left heart syndrome (HLHS) and its variants, inter-stage death accounts for an increasing proportion of mortality. Our aim was to identify the risk factors for inter-stage mortality.

METHODS

The records of 322 neonates with HLHS or a variant who underwent the Norwood procedure at our centre between 2001 and 2019 were retrospectively analysed.

RESULTS

The diagnoses included 271 neonates with HLHS (84%) and 51 with variants (16%). Aortic atresia was observed in 138 (43%) patients, mitral atresia in 91 (28%), extracardiac anomalies in 42 (13%) and genetic disorder in 14 (4%). The median age and weight of the patients at the S1P Norwood procedure were 9 (interquartile range: 7-12) days and 3.2 (2.9-3.5) kg, respectively. The median cardiopulmonary bypass time was 137 (107-163) min. Modified Blalock-Taussig shunts were used in 159 (49%) and unvalved right ventricle-to-pulmonary artery shunts in 163 (51%) patients. The number of inter-stage deaths was as follows: between S1P and stage II palliation (S2P), 61 including 38 early (<30 days) and 23 late (>30 days) deaths, and between S2P and stage III palliation, 32 deaths. Low birth weight (<2.5 kg) (odds ratio 4.37, P = 0.020) and restrictive atrial septum (odds ratio 2.97, P = 0.013) were identified as risks for early mortality. Low birth weight [hazard ratio (HR) 0.99/g, P = 0.002] was a risk for inter-stage mortality between S1P and S2P. Extracardiac anomalies (HR 4.75, P = 0.049) and significant pre-S1P atrioventricular valve regurgitation (HR: 7.72, P = 0.016) were risks for inter-stage mortality between S2P and stage III palliation. Other anatomical variables including aortic atresia, anatomical subtypes and the diameter of the ascending aorta nor shunt type were not identified as risk factors for mortality during any inter-stage period.

CONCLUSIONS

The risk factors for inter-stage attrition after the Norwood procedure were different between each stage. Preoperative factors, including birth weight, restrictive atrial septum and extracardiac anomalies, adversely affected the inter-stage mortality.

Comparison of shunt types in the neonatal Norwood procedure for single ventricle

OBJECTIVES

The ideal shunt for pulmonary blood flow, modified Blalock-Taussig shunt (MBTS) or right ventricular-pulmonary artery conduit (RVPAC) is yet to be determined. This study aimed to evaluate outcomes after the Norwood procedure according to the type of shunt.

METHODS

A total of 322 neonates with hypoplastic left heart syndrome and related anomalies who underwent the Norwood procedure at our institution between 2001 and 2019 were divided into MBTS and RVPAC groups and the outcomes after the Norwood procedure were compared between the groups with respect to mortality after each staged procedure.

RESULTS

We identified 322 consequent patients who underwent neonatal Norwood procedure for hypoplastic left heart syndrome (271 patients, 84.2%) and its variant (51 patients, 15.8%). RVPAC was performed in 163 (50.6%) patients and MBTS was performed in 159 (49.4%). There were no differences in the rate of early death (11.0% vs 12.6%, P = 0.69) or late death (7.4% vs 6.9%, P = 0.87) between the 2 groups after the Norwood procedure, and no significant difference in the number of patients who reached bidirectional cavopulmonary shunt (77.9% vs 76.1%, P = 0.69), and there was no difference in mortality after bidirectional cavopulmonary shunt (12.3% vs 7.5%, P = 0.15) or Fontan completion rate (54.0% vs 52.2%, P = 0.42) between the 2 groups. Survival at 0.5, 1, 3 and 6 years after the Norwood procedure was 81.0%, 73.8%, 67.9% and 67.0% in patients with RVPAC and 77.1%, 73.3%, 69.1% and 67.9% in patients with MBTS. There was no significant difference in the survival between the 2 groups during the median follow-up of 2.6 (interquartile ranges: 0.3-8.4, maximal 18.8) years (P = 0.97).

CONCLUSIONS

In neonates undergoing the Norwood procedure, our available data of maximal 18.8 years follow-up showed no significant difference in early mortality, inter-stage attritions, or overall survival, between MBTS and RVPAC.

Cobra-Head Cuffed Vascular Graft as Right Ventricle-to-Pulmonary Artery Shunt in Norwood Procedure

BACKGROUND

Right ventricle-to-pulmonary artery (RV-PA) shunt as a part of the Norwood procedure underwent many modifications. We present our experience with a commercially available polytetrafluoroethylene vascular graft with cobra-head cuff as an RV-PA shunt.

METHODS

A consecutive series of 52 children with hypoplastic left heart syndrome (median age 8 [range, 2-68] days, median weight 3200 [range, 2060-4400] g) underwent the Norwood procedure with a cobra-head cuffed RV-PA shunt (6 mm). The cuffed end was used for the central PA reconstruction. A retrospective analysis of clinical results, PAs development, and shunt-related complications, interventions, and technique of Glenn operation was performed. The study endpoint was Glenn operation with shunt removal or interstage death.

RESULTS

The hospital and late interstage mortality was 3.8% (n = 2 of 52) and 4% (n = 2 of 50), respectively, and was not shunt-related. During mean follow of 3.7 ± 2.5 years, 48 (92.3%) children underwent Glenn operation at a median age of 6 (range, 2.6-9.1) months. Angiography before the second stage revealed satisfactory branch PAs development (maximum and minimum McGoon ratio of 1.95 ± 0.36 and 1.38 ± 0.38, respectively). The mean maximal diameter of the left PA was smaller than that of the right PA (7.13 ± 2.1 mm vs 8.42 ± 2.2 mm; P = .017), without differences in mean minimal diameter. Two infants required stent implantation in proximal shunt end and 1 required urgent Glenn operation because distal shunt thrombosis. During Glenn operation, 11 (22.9%) children required patch reconstruction of central PAs.

CONCLUSIONS

The cobra-head cuffed graft allowed easy and reproducible reconstruction of the central PA during the Norwood procedure. Using this technique, the development of PAs is satisfactory, the rate of shunt-related complications and interventions is low, and the second stage can be performed without patch material.

Choice of shunt type for the Norwood I procedure: does it make a difference?

OBJECTIVES

This study aimed to compare pulmonary artery (PA) growth between patients who received a right ventricle-to-PA (RV-PA) shunt and those who received a modified Blalock-Taussig shunt (mBTS).

METHODS

All consecutive patients with hypoplastic left heart syndrome who underwent the Norwood I procedure between 2001 and 2017 were included in the study. Pre-stage 2 angiograms were analysed to measure the size of the PA. The Nakata index was calculated to estimate PA growth. The ratio of the right PA to left PA cross-sectional area (RPA/LPA) was used to calculate the difference in growth between the 2 branches. Study end points were shunt failure, shunt-related mortality and growth of the PAs.

RESULTS

A total of 223 patients with hypoplastic left heart syndrome (RV-PA group = 137, mBTS group = 86) underwent the Norwood I procedure, and 186 patients (RV-PA n = 116, mBTS n = 70) achieved the stage 2 procedure. PA growth was better in patients with mBTS (Nakata index: RV-PA = 282, mBTS = 315 mm2/m2, P = 0.021). LPA growth was worse compared to RPA growth in both groups (RPA/LPA: RV-PA = 1.21, mBTS = 1.29, P = 1.0). Patients with RV-PA shunts experienced more frequent shunt stenosis compared to patients with mBTS (26 vs 2, P < 0.010). Freedom from shunt failure was 83.3 ± 3.2% and 94 ± 2% at 6 months in the RV-PA and mBTS groups, respectively (P = 0.003).

CONCLUSIONS

PA growth is significantly better in patients who received an mBTS. Moreover, patients with an RV-PA shunt more frequently experienced shunt failure due to shunt stenosis. However, survival after the NW procedure is not shunt dependent and growth of the LPA is less pronounced than RPA, regardless of the shunt type.

Hypoplastic left heart syndrome: current modalities of treatment and outcomes

Hypoplastic left heart syndrome is a constellation of malformations which result from the severe underdevelopment of any left-sided cardiac structures. Once considered to be universally fatal, the prognosis for this condition has tremendously improved over the past four decades since the work of William Norwood in the early 1980s. Today, a staged surgical approach is applied for palliating this distinctive cohort of patients, in which they undergo three operative procedures in the first 10 years of their life. Advancements in medical technologies, surgical techniques, and our growing experience in the management of HLHS have made survival into adulthood a possibility. Through this review, we present the different phases of the staged approach with primary focus on stage 1-its modifications, current technique, alternatives, and latest outcomes.

Early results of ring-reinforced conduit and curved porcine patch in Sano-Norwood procedure

BACKGROUND

Patch augmentation of the aortic arch as well as construction of an unobstructed pulmonary blood supply are two important surgical targets in patients with hypoplastic left heart syndrome. In this report, we aimed to present our preliminary results with a combination of two relatively new approaches in Norwood-Sano procedure.

METHODS

A retrospective analysis was performed in 10 newborns with the diagnosis of hypoplastic left heart syndrome. Our surgical approach incorporated the interposition of a 6.0-mm ring-reinforced tube graft with the "dunked technique" between the right ventricle and the pulmonary artery; and reconstruction of the aortic arch using a curved porcine pericardial patch which is specifically designed for the Norwood procedure.

RESULTS

Mean age and body weight at the time of the Sano-Norwood operation were 7.3 ± 2.4 days and 3164 ± 406 g, respectively. We encountered 1 (10%) early and 1 (10%) late mortality. All of the patients were discharged without any residual gradients at the aortic arch. Four out of eight patients underwent stage 2 bidirectional cavopulmonary anastomosis at a median age of 5 months (range, 4-6 months). Pericardial patch augmentation of the left pulmonary artery was deemed mandatory in one of our patients.

CONCLUSIONS

The dunked technique of interposing a ring-reinforced conduit between the right ventricle and pulmonary artery along with the utilization of a curved porcine pericardial patch specifically designed for aortic arch reconstruction are promising modifications of the Sano-Norwood procedure in newborns with hypoplastic left heart syndrome.

Easy Fenestration Technique for Extracardiac Fontan Operation

During an extracardiac conduit type of Fontan operation, fenestration is not always technically easy, particularly when the right atrium is small and located posteriorly. We describe here an easy technique for performing an anastomosis of a polytetrafluoroethylene ringed graft to the atrium for fenestration in the setting of an extracardiac conduit Fontan operation. The surgical technique starts with a purse string suture that is customized to fit the atrium and utilizes a ringed graft that is inserted into the right atrium through the purse string, which is then tied.

Periscope modification of right ventricle-to-pulmonary artery shunt in Norwood operation

Given the purported hemodynamic advantages of the right ventricle (RV) to pulmonary artery (PA) conduit, many surgeons have adopted it as their preferred source of pulmonary blood flow during stage I palliation for hypoplastic left heart syndrome. Potential disadvantages of the RV-PA shunt include ventricular dysfunction, pseudoaneurysm formation, arrhythmia, and conduit obstruction, which can lead to a higher rate of unplanned reinterventions. The "dunk" technique was described to reduce the RV incision and proximal conduit obstruction; however, insertion of the ringed graft from the epicardium can be cumbersome and risk RV injury. We introduce a simplified, alternative method of placing the conduit, which we call the periscope technique, whereby the graft is withdrawn from within the RV cavity.

Ring-reinforced Sano conduit at Norwood stage I reduces proximal conduit obstruction

BACKGROUND

Reinterventions for proximal conduit obstruction or on the pulmonary arteries are frequent after the Sano-modified stage I Norwood palliation of hypoplastic left heart syndrome. We report our initial experience with a modified Sano technique using a ring-reinforced graft inserted transmurally through the right ventricle with a limited ventriculotomy.

METHODS

All patients who underwent the Sano-modified stage I Norwood procedure using a modified "dunked" technique from September 2010 to September 2012 at our institution were reviewed. An historical control group consisted of patients undergoing the traditional Sano right ventricle-to-pulmonary artery conduit anastomosed to the epicardium. The primary outcome measures included death, reintervention on the Sano and pulmonary arteries, and ventricular function.

RESULTS

The study included 29 patients. No patients required intervention on the Sano conduit, pulmonary arteries, or aortic arch before discharge after the stage I procedure. During a median follow-up of 20 months (range, 26 days to 3.3 years), survival was estimated at 96.6% ± 3.4% at 1 month and 86.2% ± 6.4% at the latest follow-up. One patient underwent heart transplantation. No interstage intervention was required on the proximal or distal Sano conduit. Intervention was required on the midportion of the conduit in 1 patient and on the pulmonary arteries in 3 patients. At the time of the bidirectional Glenn anastomosis, freedom from conduit and pulmonary artery intervention was estimated at 92.3% ± 7.4% and 90.1% ± 8.7%, respectively, and global right ventricular dysfunction was mild or less in 84% (16 of 19) of patients.

CONCLUSIONS

The ring-reinforced right ventricle-to-pulmonary artery Sano conduit transmurally inserted into the right ventricle provides acceptable results, with a low incidence of interstage reinterventions in patients undergoing stage I palliation.

Functional and pathological characteristics of reversible remodeling in a canine right ventricle in response to volume overloading and volume unloading

Purposes

Patients who undergo right ventricular (RV) outflow augmentation inevitably develop RV remodeling due to pulmonary insufficiency-related volume overload (VOL). However, the reversibility of this remodeling is not fully understood. The goal of this study was to establish an animal model of VOL and unloading to characterize the functional and pathological characteristics and reversibility of RV remodeling.

Methods

VOL-RV was successfully induced by establishing direct RV-pulmonary artery (PA) bypass for 12 weeks in beagle canines. There were no procedure-related mortalities (n = 8).

Results

The RV developed typical functional features of VOL-related remodeling, such as a significant increase in end-diastolic/systolic volume and end-systolic pressure and a significant reduction in ejection fraction at 12 weeks, as assessed by three-dimensional echocardiography and cardiac catheterization. The RV developed typical pathological signs of remodeling, microstructural disorganization of cardiomyocytes, and/or structural/functional deterioration of the mitochondria. Volume unloading by division of the RV-PA bypass reversed the increase in the end-systolic/diastolic volume over 4 weeks when compared with a sham operation (n = 4 each). In addition, the bypass division also reversed the pathological changes seen in VOL-RV.

Conclusions

VOL-RV that yielded typical functional and pathological features of RV remodeling was reproducibly achieved by direct RV-PA bypass in canines. The RV remodeling due to VOL was functionally and pathologically reversed by volume unloading via the bypass division.

Treatment of right ventricle to pulmonary artery conduit stenosis in infants with hypoplastic left heart syndrome

OBJECTIVES

To determine the incidence of right ventricle-to-pulmonary artery (RV-PA) conduit stenosis after the Norwood I operation in patients with hypoplastic left heart syndrome (HLHS), and to determine whether the treatment strategy of RV-PA conduit stenosis has an influence on interstage and overall survival.

METHODS

Ninety-six patients had a Norwood operation with RV-PA conduit between 2002 and 2011. Details of reoperations/interventions due to conduit obstruction prior to bidirectional superior cavopulmonary anastomosis (BSCPA) were collected.

RESULTS

Overall pre-BSCPA mortality was 17%, early mortality after Norwood, 6%. Early angiography was performed in 34 patients due to desaturation at a median of 8 days after the Norwood operation. Fifteen patients (16%) were diagnosed with RV-PA conduit stenosis that required treatment. The location of the conduit stenosis was significantly different in the patients with non-ringed (proximal) and the patients with ring-enforced conduit (distal), P = 0.004. In 6 patients, a surgical revision of the conduit was performed; 3 of them died prior to BSCPA. Another 6 patients had a stent implantation and 3 were treated with balloon dilatation followed by a BSCPA in the subsequent 2 weeks. All patients who were treated interventionally for RV-PA conduit obstruction had a successful BSCPA. Patients who received a surgical RV-PA conduit revision had a significantly higher interstage (P = 0.044) and overall mortality (P = 0.011) than those who received a stent or balloon dilatation of the stenosis followed by an early BSCPA.

CONCLUSIONS

RV-PA conduit obstruction after Norwood I procedure in patients with HLHS can be safely and effectively treated by stent implantation, balloon dilatation and early BSCPA. Surgical revision of the RV-PA conduit can be reserved for patients in whom an interventional approach fails, and an early BSCPA is not an option.

Interventions after Norwood procedure: comparison of Sano and modified Blalock-Taussig shunt

Improved results have evolved from the modified Norwood procedure (NP). This study compares the incidence of interventions after NP with the Sano (n = 37) and modified Blalock-Taussig (BT n = 70) shunt. Incidence, location, interval of interventions, and weight were retrospectively analysed for 107 neonates undergoing NP during the period from October 2002 to December 2009. Forty-six (43.0 %) patients underwent interventions, mostly for dilatation of the aortic arch ([DAA] n = 26 [24.3 %]; Sano n = 10, BT n = 16, p = 0.6), dilatation of the shunt ([DS] n = 15 [14.0 %]; Sano n = 11, BT n = 4; p = 0.002), or closure of aortopulmonary collaterals ([APC] n = 15 [14.0 %]; Sano n = 3, BT n = 12; p = 0.08). Mean interval after NP and body weight at DAA, DS, and APC were 72.4 ± 18.9, 108.5 ± 15.8, and 110.7 ± 17.8 days and 4.5 ± 1.3, 4.9 ± 1.9, 5.3 ± 1.2 kg, respectively. The interventions were not associated with mortality but with a greater rate of complications (9 of 46 [21.4 %]) compared with the rate after diagnostic catheterization (0 of 45, p = 0.03). Complications included closure of the femoral or subclavian artery (n = 5), cerebral embolic or bleeding events (n = 4), cardiopulmonary resuscitation (n = 3), and temporary heart block (n = 2). Actuarial survival was similar from the postoperative month 8 onward at 78.6 ± 4.9 % (95 % confidence interval [CI] 67.0-86.5 %) for Sano and 78.4 ± 6.8 % (95 % CI 61.4-88.6 %) for BT (p = 0.95). Interventions after NP were common irrespective of shunt type. However, a significantly greater rate of shunt interventions was noted in the Sano group. In particular, interventions addressing the aortic arch and the shunt were related with a significant rate of complications.

The Norwood procedure: in favor of the RV-PA conduit

Evolution of the Norwood procedure has culminated in there currently being three treatment strategies available for initial management: the 'classical' Norwood (utilizing a Blalock-Taussig shunt), the Norwood with right-ventricle to pulmonary artery (RV-PA) conduit, and the 'hybrid' Norwood procedure utilizing bilateral pulmonary artery banding and ductal stenting. Each variant has its potential advantages and disadvantages, and this paper looks to examine the evidence in favor of each strategy, with emphasis on the supportive data for the RV-PA conduit. The 'classical' procedure has the benefit of the greatest accumulated surgical experience and avoids any incision into the ventricle. However, the diastolic run-off of the Blalock-Taussig shunt can cause hemodynamic instability and unpredictable coronary steal phenomenon. The RV-PA conduit has the advantage of maintaining diastolic pressure with a more stable postoperative course, but at the cost of a ventriculotomy that may have detrimental long-term sequelae. The 'hybrid' procedure has the advantage of avoiding cardiopulmonary bypass, but does not always secure coronary blood flow and has a high inter-stage morbidity and reintervention rate. The evidence shows that each technique may have its place in future management, and that treatment algorithms could emerge that direct the choice of procedure for specific patient groups.

Perioperative care of the infant with single ventricle physiology

OPINION STATEMENT

Among patients with congenital heart defects, neonates with single ventricle disease continue to challenge clinicians despite significant improvements in survival over the past 30 years. The cardiac anatomical variants associated with the term "single ventricle" are characterized by severe hypoplasia (or absence) of either ventricle, typically in association with obstruction or atresia of either the pulmonary or systemic outflow tracts. Physiologically, the single ventricle receives both pulmonary and systemic venous blood and ejects simultaneously into the pulmonary and systemic circulations, a pattern commonly referred to as single ventricle physiology. Medical and surgical management strategies, though palliative, are aimed at achieving the optimal balance of systemic blood flow and pulmonary blood flow to maximize oxygen delivery. Patients with single ventricle physiology have a greater risk of dying than those with biventricular circulations and are generally committed to multiple palliative interventions throughout childhood with considerable risk. Surgical intervention in the newborn period involves Norwood Stage I palliation, placement of a systemic-to-pulmonary artery shunt, or banding of the pulmonary artery, depending on the status of the outflow tracts. Heart transplantation is offered as the initial approach in some centers. The management strategy and the actual delivery of care from the time of birth (or at time of diagnosis) through the postoperative period is crucial to optimize the short-term and long-term outcomes. Whereas survival following initial palliation in experienced centers is as high as 95%, emphasis is now appropriately shifting toward the control of in-hospital morbidity and optimizing long-term functional outcome. Centers are continually striving to gather and apply new knowledge related to the underlying anatomical and physiologic problems while seeking to improve decision making and care of the patient with single ventricle physiology.