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Eur J Cardiothorac Surg 2007;31:1013-1021. doi:10.1016/j.ejcts.2007.03.015
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved

Review

Management options in neonates and infants with critical left ventricular outflow tract obstruction

Bahaaldin Alsoufia,b,*, Tara Karamloua, Brian W. McCrindlea, Christopher A. Caldaronea

a The Cardiac Center, The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada
b King Faisal Heart Institute at King Faisal Specialist Hospital and Research Center. Riyadh, Saudi Arabia

Received 6 January 2007; received in revised form 6 March 2007; accepted 9 March 2007.

* Corresponding author. Address: King Faisal Heart Institute (MBC 16), King Faisal Specialist Hospital and Research Center, P.O. Box 3354, Riyadh 11211, Saudi Arabia. Tel.: +966 1 464 7272x39455; fax: +966 1 442 7791. (Email: balsoufi{at}hotmail.com).


   Abstract
Top
 Abstract
1. Introduction
 2. Pathophysiology and clinical...
 3. Treatment
 4. Summary
 References
 
Despite being one of the most common congenital cardiac abnormalities, the treatment of critical left ventricular outflow tract obstruction (LVOTO) in the neonate and infant remains a significant challenge. Critical LVOTO in the neonate and infant includes continuous and diverse spectrum of anatomic diagnoses ranging from hypoplastic left heart complex to isolated aortic valvular stenosis with otherwise normally formed left heart structures. Depending on related anatomic features, there are multiple single ventricle and biventricular management strategies available for patients with critical LVOTO; all of which carry significant risk of death and requirement for future interventions. Because of the wide array of morphologic lesions and physiologic manifestations, application of the currently available published data to guide decision making in the individual patients can be challenging. Therefore, the aim of this review is to describe the different therapeutic strategies that can be applied to neonates presenting with critical LVOTO taking into consideration each patient's unique physiologic and anatomic findings.

Key Words: Congenital heart disease • Aortic stenosis • Valvotomy • Transplantation • Norwood


   1. Introduction
Top
 Abstract
 1. Introduction
2. Pathophysiology and clinical...
 3. Treatment
 4. Summary
 References
 
Despite being one of the most common congenital cardiac abnormalities, the treatment of critical left ventricular outflow tract obstruction (LVOTO) in the neonate and infant remains a significant challenge.

Taken as a group, neonates with LVOTO present across a wide morphologic spectrum of hypoplasia of left heart structures with variable hemodynamic manifestations which are based on the level and the severity of the obstruction, the related hypoplasia of the left ventricle and the mitral valve, and associated lesions such as ventricular septal defect and aortic arch hypoplasia. These factors influence the treatment strategies that can be applied to patients with critical LVOTO, such as the choice of single ventricle versus biventricular repair, and the particular surgical or catheter-based methods employed to achieve relief of the obstruction.

Because of the wide array of morphologic lesions and physiologic manifestations, application of the currently available published data to guide decision making in the individual patients can be challenging. Therefore, the aim of this review is to describe the different therapeutic strategies that can be applied to neonates presenting with critical LVOTO taking into consideration each patient's unique physiologic and anatomic findings.


   2. Pathophysiology and clinical presentation
Top
 Abstract
 1. Introduction
 2. Pathophysiology and clinical...
3. Treatment
 4. Summary
 References
 
During fetal development, severe LVOTO exposes the left ventricle to increased afterload and results in ventricular hypertrophy and myocardial dysfunction. Moreover, chronic in-utero subendocardial ischemia secondary to hypertrophy and increased intracavitary pressure can lead to coronary ischemia and the development of endocardial fibroelastosis which further impairs the ventricular function. Additionally, reduced antegrade blood flow through the aortic valve will predispose to underdevelopment of the left heart structures and hypoplasia of the mitral valve, left ventricle, and aortic arch.

Patient presentation varies with the severity of LVOTO and the degree of associated ventricular hypoplasia and dysfunction. Neonates with critical aortic stenosis have a brisk and dramatic presentation soon after birth. As the ductus arteriosus begins to close, neonates with critical LVOTO experience decreased systemic and coronary perfusion, acute hemodynamic deterioration with cardiovascular collapse, acidosis, end organ injury, and shock. Resuscitation of the patients and the use of prostaglandins to restore ductal patency are needed. Following stabilization of the patients, complete echocardiographic evaluation is required to assess the severity and the levels of obstruction, associated cardiac abnormalities and related hypoplasia of the aortic arch and left heart structures.

Neonates and infants with lesser degrees of obstruction may present with failure to thrive and tachypnea due to increased work of breathing in association with pulmonary vascular congestion due to left atrial hypertension. These infants require early intervention due to persistent high left ventricular afterload, myocardial dysfunction, and poor systemic cardiac output.


   3. Treatment
Top
 Abstract
 1. Introduction
 2. Pathophysiology and clinical...
 3. Treatment
4. Summary
 References
 
Only an estimated 10–15% of all patients with congenital aortic valve stenosis present within the first year of life [1,2]. However, when neonates and infants do present with aortic valve stenosis, they face significant morbidity and mortality [1–7]. The management strategy is largely based on the assessment of the infant's clinical status and the complete understanding of the underlying anatomic defects and the degree of the hypoplasia of the left heart structures. The anatomic spectrum of critical LVOTO ranges from isolated aortic valvular obstruction with otherwise normal cardiac anatomy to hypoplastic left heart syndrome (HLHS) with near absence of the left ventricle and severe hypoplasia of the aortic arch. Three parts of the ‘spectrum of severity’ can be defined and each present unique clinical decision-making problems.

3.1 The single-ventricle end of the spectrum
The single ventricle end of the spectrum is characterized by a severe degree of underdevelopment of the left heart–aorta complex, resulting in obstruction to systemic cardiac output and the inability of the left heart to support the systemic circulation. The hypoplasia of the left heart structures renders it impossible to achieve a two ventricle repair, short of heart transplantation, and those patients usually require single ventricle multistage palliation. The prognosis of newborns undergoing staged palliation in the current decade has dramatically improved through refinement of established surgical techniques and the introduction of new and rapidly evolving treatment strategies [8–11].

3.1.1 Staged surgical palliation with the Norwood procedure
The Norwood procedure is the most commonly performed initial palliative procedure for patients undergoing staged surgical palliation in the neonatal period. A second-stage procedure, the bidirectional cavopulmonary shunt or hemi-Fontan procedure is typically performed at 4–6 months of age and results in removal of the ventricular volume load by the anastomosis of the superior vena cava to the pulmonary arteries. At a third stage, typically at 2–4 years of age, a Fontan procedure is performed to channel the remaining systemic venous return from the inferior vena cava return to the pulmonary arteries [8,12].

The standard Norwood procedure utilizes a modified Blalock-Taussig shunt that is constructed between the innominate and the pulmonary artery as the source of pulmonary blood flow while the modified Norwood operation utilizes a right ventricular to pulmonary artery conduit that may offer the advantage of eliminating the shunt morbidity including diastolic runoff into the pulmonary circulation with subsequent coronary steal. The utilization of contemporary measures in the postoperative management following the Norwood operation including the use of systemic vasodilators such as phenoxybenzamine and the continuous monitoring of mixed venous saturation enabled some centers to achieve hospital survival exceeding 90% in selected groups of patients [8–11]. Several operative risk factors have been identified including low birth weight, prematurity, significant associated noncardiac congenital conditions, severe preoperative obstruction to pulmonary venous return, older era of surgery, tricuspid valve regurgitation, smaller ascending aorta, and increased circulatory arrest times [11–16].

3.1.2 Staged surgical palliation with ‘hybrid’ techniques
More recently, several groups have reported favorable preliminary experience with the use of hybrid techniques as an alternative to the Norwood sequence including initial first stage bilateral pulmonary artery banding and ductal stenting (PAB/DS) in the neonatal period followed by arch and neoaortic reconstruction with cavopulmonary shunt at 4–6 months of age [17–20]. This hybrid strategy offers the advantage of avoiding cardiopulmonary bypass, cardioplegic arrest, and circulatory arrest in the neonatal period and deferral of major arch reconstruction until 4–6 months of age. The strategy is predicated on the hypothesis that an infant is less vulnerable to post-operative myocardial and neurologic injury than a neonate and therefore the hybrid strategy will potentially be associated with improved neurodevelopmental and functional outcomes [17–20]. In addition, by deferring the ‘big’ operation until 4–6 months of age allows the patient to leave the operating room with a cavopulmonary shunt (in-series circulation) rather than a balanced circulation as is obtained after a Norwood procedure. Because an in-series circulation is more stable than a balanced circulation, proponents of the hybrid strategy contend that there will be an overall survival advantage associated with the hybrid strategy.

3.1.3 Transplantation
Finally, innovations in peri-transplant management have contributed to decreased infant mortality while awaiting transplantation which historically accounted for 21–37% of transplant mortality [21–23]. Innovations include the development of the PAB/DS hybrid procedure for pre-transplant palliation which can be used to control pulmonary blood flow and allow cessation of prostaglandin therapy with subsequent hospital discharge while awaiting a donor organ. In addition, the introduction of ABO blood group incompatible heart transplants increase the heart donor pool. Infant survival following transplantation has significantly improved in the last decade, and future progress can be expected with continued advances in the understanding of immunologic response and tolerance and the development of new immunosuppressive agents [21,22,24,25].

The diversity of available management options, the rapidity of evolution of new management techniques, the tendency of single institutions to focus on a single strategy, and the relatively small number of patients in most reported series have made comparison between management strategies difficult. Consequently, there are very few published reports where controlled comparisons were made between these various options. Multi-institutional studies, such as a study currently enrolling patients with critical LVOTO organized by the Congenital Heart Surgeons Society (CHSS), are needed to compare outcomes of different treatment strategies while controlling for individual patient morphologic characteristics.

Table 1 summarizes selected surgical outcomes in patients with aortic valve stenosis/atresia and hypoplasia of the left heart structures treated with single ventricle management strategies.


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  		Table 1 Selected results of single ventricle treatment strategies for patients with critical aortic stenosis/atresia and hypoplasia of the left heart structures including heart transplantation, staged and hybrid palliative strategies
 
3.2 The two-ventricle end of the spectrum
The two-ventricle end of the spectrum can be equally complex. Patients in this group have obstruction localized to the aortic valve and sub-valvular area with two well developed ventricles with or without a ventricular septal defect (VSD). These patients have a large number of two-ventricle options available to them depending on individual morphologic characteristics (e.g. presence or absence of a VSD, morphology of the aortic valve, levels of obstruction, etc.). These options include percutaneous aortic balloon valvuloplasty, surgical aortic valvotomy, neonatal Ross or Ross/Konno procedure, the Yasui procedure, and mechanical aortic valve replacement with enlargement of the left ventricular outflow tract.

3.2.1 Surgical valvotomy
Before the development of percutaneous balloon aortic valvuloplasty, surgical valvotomy was the mainstay of treatment of critical aortic stenosis in neonates and infants. Different approaches such as trans-ventricular closed aortic valvotomy, open valvotomy with inflow occlusion or with cardiopulmonary bypass (CPB) were developed [1,4,5,32–37]. With improved safety of CPB and myocardial protection, open valvotomy with CPB became the preferred technique by almost all surgeons. The advantage of open valvotomy is that it allows detailed examination of the valve and accurate valvotomy; the disadvantages include the surgical morbidity and increased complexity of future surgery due to redo sternotomy. Although precutaneous balloon aortic valvuloplasty has replaced surgery to become the preferred technique in most centers, surgical valvotomy remains favored by some. Several risk factors for increased operative mortality have been identified including the presence of endocardial fibroelastosis, presence of hypoplastic left ventricle, or aortic annulus, presence of associated cardiovascular anomalies, extremely small neonates and earlier era surgery [2,5,33].

Recently, a study from Birmingham suggested that long-term outcomes after aortic valvotomy are significantly better in infants in whom surgery results in trileaflet rather than bileaflet anatomy with 10 years survival of 100% versus 85%, respectively, and freedom from aortic reoperation of 92% versus 45%, respectively [38].

Results of surgical valvotomy listing operative mortality, time related survival and freedom from re-intervention are presented in Table 2 .


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  		Table 2 Selected results of surgical aortic valvotomy in neonates and infants
 
3.2.2 Percutaneous balloon aortic valvuloplasty
Since the first report of successful pecutaneous balloon aortic valvuloplasty (BAVP) for aortic stenosis in infancy, this modality has become the favored technique in many institutions. Vascular access is usually obtained with an antegrade approach using the umbilical or the femoral arteries. However, retrograde approach using the carotid artery has been described [40,41]. In a report comparing retrograde and antegrade balloon aortic valvuloplasty, antegrade approach was associated with diminished morbidity compared with retrograde approach [40,41]. Advantages of percutaneous intervention include the avoidance of surgical morbidity associated with cardiopulmonary bypass. Disadvantages include vascular access complications, inability to precisely determine where the leaflets will tear and subsequent potential for aortic valve insufficiency, and rarely mitral valve injury [41]. It should be recognized that it is important not to overdilate the valve, and that the goal is not complete elimination but improvement of the gradient until the patient is older and bigger, at which point the procedure can be repeated.

Several risk factors were identified including extremely young neonates, older era of intervention and infants with hypoplastic left ventricle or aortic annulus [2,6,7].

A recent review from Boston of 113 infants ≤ 60 days of age who underwent BAVP showed a mean relative gradient reduction of 54 ± 26%. However, significant aortic regurgitation (AR) developed in 15% of patients. On follow-up, there was a steady increase in the frequency of significant regurgitation with freedom from moderate or severe AR of 65% at 5 years. The aortic annulus diameter and left ventricular end-diastolic dimension Z-scores increased to within the normal range within 1–2 years. Reintervention-free survival on the LV outflow tract was 48% at 5 years and freedom from aortic valve replacement was 84% at 5 years [7].

Outcomes of selected series of infants undergoing BAVP are detailed in Table 3 .


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  		Table 3 Selected results of percutaneous balloon aortic valvuloplasty in neonates and infants
 
3.2.3 Percutaneous valvuloplasty versus surgical valvotomy
Both surgical valvotomy and percutaneous balloon valvuloplasty are associated with important mortality and morbidity such as residual or recurrent valve dysfunction, and the need for reintervention [2,6,7,32,34,37,38]. There are no prospectively randomized studies comparing outcomes between the two techniques. Numerous reports cited the early and late outcomes of either one procedure or the other, but few compared surgical versus percutaneous techniques and those that did are limited by the lack of adjustments between the two groups [2,37,39].

In a retrospective multi-institutional study by the Congenital Heart Surgeons Society, 110 patients underwent either surgical aortic valvotomy (SAV: n = 28) or percutaneous balloon aortic valvuloplasty (BAPV: n = 82) [2]. The study demonstrated that, while controlling for pre-intervention morphology, BAPV was more effective in relieving stenosis than SAV as evidenced by a greater mean percent reduction in systolic gradient with BAPV than SAV (65% vs 41%) and higher residual median gradients in the SAV versus BAPV group (36 mm Hg vs 20 mm Hg). However, BAPV was also associated with a greater likelihood of important aortic regurgitation than SAV (18% vs 3%). Freedom from re-intervention was similar for the two groups (91% at 1 month and 48% at 5 years). Significant factors for re-intervention included pre-valvuloplasty use of inotropic agents, the presence of post-procedural moderate to severe aortic valve regurgitation, and a lower weight at initial intervention. The high re-intervention rate emphasizes the palliative role of valvuloplasty in the neonatal period. Risk-adjusted Freedom from death was also similar between the two groups and was 82% at 1 month and 74% at 1 year. Risk factors for death included mechanical ventilation before valvotomy and anatomic factors including smaller aortic valve diameter at the level of the annulus, the sinotubular junction, or the subaortic region indicating that many of those patients may have been inappropriately triaged into the biventricular tract and that they may have been better served by a palliative single ventricle approach [2].

3.2.4 Aortic valve replacement
Rarely, aortic valve replacement is needed in neonates and infants with LVOT obstruction. Usual indications include patients with complex multi-level aortic and sub-aortic LVOT obstruction or those with severe congestive heart failure and aortic insufficiency complicating percutaneous aortic balloon valvuloplasty. Although it is possible to replace the aortic valve with a mechanical prosthesis in addition to aortic root enlarging technique such as the Konno procedure in neonates and small infants; this procedure has been associated with a very high early re-intervention rate and poor survival [45]. Several groups have reported successful aortic valve replacement with a pulmonary autograft (Ross procedure) which can be associated with aortic root enlargement (Ross–Konno procedure) [1,46–49].

The Ross procedure, although more complex, will provide excellent normalization of hemodynamics and regression of left ventricular hypertrophy by avoiding residual lesions, does not require anticoagulation, will allow for evolution of left heart structures and for growth in the aortic position as the infant gets older. The pulmonary homograft used for reconstruction of the right ventricular outflow tract is subject to calcific degeneration which, in addition to its failure to grow with the infant, will require re-operation and conduit replacement [1,46–49].

In addition, potential dilatation of the neo-aortic root leading to progression of AI is of concern, especially in the setting of geometric mismatch of aortic and pulmonary roots and bicuspid regurgitant aortic valve [50,51]. These specific subsets of patients have been identified by several groups to have a higher risk of autograft dilatation and recurrence of AI. In a recent series, the Ross procedure was performed in 27 infants <18 months of age. There were three early deaths and no late deaths. Freedom from reintervention for homograft dysfunction was 87% at 8 years and freedom from autograft reintervention was 100%. On follow-up echocardiograms, the estimated peak autograft gradient was <10 mmHg in 16/17 patients. 13/17 patients had no autograft insufficiency and 4/17 had mild insufficiency. Dilatation of the autograft occurred during the first year after surgery and stabilized thereafter. Homograft reintervention was needed in 13% within 8 years [49]. Despite the need for reoperation and potential for autograft root dilation, the Ross and the Ross–Konno procedure remain the best choice for aortic valve replacement in infants with multi-level LVOT obstruction or severe aortic insufficiency following valvuloplasty [47–49].

3.3 Determinants of single versus biventricular approach in borderline left ventricular development
The ‘middle’ of the spectrum is perhaps the most complex in terms of clinical decision making. In this ‘grey zone’, patients have borderline development of the left ventricle and the mitral valve, and they may undergo either one- or two-ventricle palliation [52–55]. Single ventricle palliative options, although possible, may forfeit the opportunity for appropriate candidates to undergo two-ventricle repair. Conversely, aggressive attempts to attain two-ventricle status may come at the relative cost of greater risk of death and higher subsequent morbidity in terms of re-operation and catheterizations. The importance of proper treatment selection is reflected by the higher mortality in older unstratified series that failed to address the heterogeneity of this disease and to tailor the treatment to specific patient anatomy. The significance of appropriate initial triage cannot be overestimated as multiple reports have shown universally poor results in those patients requiring ‘crossover’ between strategies [52–55].

Several studies have attempted to identify pre-operative predictors of suitability for single ventricle versus biventricular repair in infants with critical aortic stenosis and borderline development of left heart structures. Hammon et al. [52] proposed an angiographically derived 20 ml/m2 threshold end-diastolic volume for successful biventricular repair. Rhodes et al. identified several clinical risk factors for successful biventricular repair including mitral valve area less than 4.75 cm2/m2, long axis dimension of the left ventricle relative to the long axis dimension of the heart less than 0.8, diameter of the aortic root less than 3.5 cm/m2 and left ventricular mass less than 35 g/m2. The presence of more than one of those risk factors predicted high mortality following biventricular repair. Subsequently, he proposed a score that is derived from a multivariable regression equation of the following form: (14 (body surface area) + 0.94 (indexed aortic root diameter) + 4.78 (LV/RV long axis ratio) + 0.16 (indexed mitral valve area) – 12) with a discriminating score less than –0.35 predictive of death after a biventricular repair [54]. However, the Rhodes score was based on retrospective data from a small group of 65 patients with critical AS who were pre-selected for biventricular repair and subsequent investigation from multiple different studies have shown poor discrimination with the Rhodes score when applied to neonates with multiple levels left heart obstruction or whose primary pathology is other than critical AS [55–57].

The Congenital Heart Surgeon's Society (CHSS) reported a multi-institutional study of 320 neonates with critical aortic stenosis enrolled between 1994 and 2000 [53]. Biventricular repair was performed in 116 patients whereas an initial Norwood procedure was performed in 179 patients. Five-year survival was 70% for neonates undergoing biventricular repair and 60% for neonates undergoing Norwood sequence. Complex statistical techniques were then used to model the magnitude and direction of the survival benefit for the Norwood procedure over the two-ventricle repair pathway. Independent factors associated with greater survival benefit with the Norwood pathway included younger age at entry, higher grade of endocardial fibroelastosis, lower Z-score of the aortic valve at the level of the sinuses of Valsalva, larger ascending aortic diameter, absence of moderate or severe tricuspid regurgitation and lower Z-score of the left ventricular length. Subsequently a regression equation was formulated to predict patient's survival benefit, with a positive number representing improved survival with a Norwood procedure, a negative number representing improved survival with a biventricular repair strategy, and the magnitude of the number representing the degree of predicted survival benefit [53]. The final form of this equation is available through the CHSS website at www.chssdc.org. Importantly, the CHSS demonstrated that currently used selection criteria resulted in inappropriate patient triage in a significant number of neonates. Predicted survival benefit favored the Norwood procedure in 50% of patients who had biventricular repair, and it favored biventricular repair in 20% of patients who had the Norwood procedure. Choosing the ‘correct’ management strategy could have resulted in to a substantial survival advantage for patients in the cohort in whom the ‘incorrect’ management option was chosen [53].

Although the CHSS study is the most detailed and sophisticated analysis involving the largest number of patients, the validity of this equation to determine the optimal surgical option for each patient has not been prospectively validated, In addition, the use of the score does not allow prediction of long-term functional and quality of life outcomes which are important considerations in choosing a management strategy for an individual patient, Moreover, refinements of the prediction model are needed to include newer management strategies, and to calibrate with currently achievable clinical outcomes.

3.4 Special situations
3.4.1 Left heart hypoplasia and neonatal aortic arch obstruction
Some patients often present with severe aortic coarctation and arch hypoplasia associated with left ventricular outflow obstruction due to hypoplasia of the aortic valve rather than intrinsic cusp stenosis or atresia, in addition to underdevelopment of the mitral valve and the left ventricle with or without ventricular septal defects. Several groups have reported subsequent growth of the left ventricle, aortic and mitral valves following biventricular repair in patients with hypoplasia of the left ventricle without intrinsic aortic stenosis [56–59]. Although associated with high reoperation rate for recurrent coarctation, residual LVOTO or mitral stenosis, biventricular repair was feasible in those patients [56–59]. Tchervenkov [60] suggested several criteria to define those patients suitable for biventricular repair including the presence of antegrade flow through the left heart into the ascending aorta and proximal arch, the absence of intrinsic stenosis of the aortic and mitral valves (e.g. the functional obstruction exists by virtue of hypoplasia of the valves and the left ventricle rather than fibrosis and dysplasia of heart structures), the presence of adequate left ventricular function, and the absence of endocardial fibroelastosis.

The principles of biventricular repair include the elimination of any anatomic extracardiac afterload by enlarging the ascending aorta and the arch with patch augmentation and full preloading of the left heart by closing the atrial and ventricular septal defects, with an initial conservative approach to the mitral and aortic valves and the left ventricular outflow tract. Additionally, aortic valve commisurotomy was performed by some groups [60].

Patients with antegrade flow into the ascending aorta with small but nonstenotic aortic valve associated with ductal dependant obstruction of the aorta have been reported to be able to undergo biventricular repair. In this subset of patients, there was no operative mortality despite the fact that all those patients had scores calculated using the Rhodes equation that would have predicted the need for single ventricle repair. These findings indicated that the score was not valid for this subgroup of patients with left ventricular outflow obstruction [56,57].

Published surgical results are summarized in Table 4 .


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  		Table 4 Biventricular surgical repair results in patients with hypoplastic aortic arch/coarctation and left ventricular hypoplasia and patients with critical aortic stenosis/atreia and ventricular septal defect
 
3.4.2 Critical aortic stenosis or atresia with ventricular septal defect
Another special group of patients are those having either critical aortic stenosis or atresia associated with ventricular septal defect and a well developed left ventricle. Those patients can be candidates for biventricular repair as described by Yasui in 1987. Repair strategy consists of establishing continuity between the pulmonary artery and the aorta by performing the Damus–Kaye–Stanzel anastomosis and creating a neo-aorta, in addition to constructing an inter-ventricular baffle from left ventricle through the ventricular septal defect into the neo-aorta and placing a conduit from the right ventricle to the pulmonary artery.

Another surgical option can be the Ross–Konno aortic valve replacement concomitantly with aortic arch repair. Several groups have reported small case series of patients using these techniques to obtain biventricular repair. In most of those series, however, the patients had undergone the Norwood operation as the initial palliative procedure in the neonatal period followed by subsequent conversion to biventricular repair at a later date. The value of a Norwood-type staging procedure followed by subsequent conversion to a biventricular repair versus improved predictive models to identify two-ventricle candidates in the neonatal period who undergo definitive two-ventricle procedures in the neonatal period remains to be demonstrated.

Currently reported surgical results are summarized in Table 4.


   4. Summary
Top
 Abstract
 1. Introduction
 2. Pathophysiology and clinical...
 3. Treatment
 4. Summary
References
 
Critical left ventricular outflow tract obstruction (LVOTO) in the neonate and infant includes continuous and diverse spectrum of anatomic diagnoses ranging from hypoplastic left heart complex to isolated aortic valvular stenosis with otherwise normally formed left heart structures. Depending on related anatomic features, there are multiple single ventricle and biventricular management strategies available for patients with critical LVOTO; all of which carry significant risk of death and requirement for future interventions. (Fig. 1 ) Because of the wide array of management strategies available, the diverse anatomic spectrum of critical LVOTO, and the relatively small population of patients treated at any single center, optimum management strategies across each morphologic spectrum have not been well defined and represent an important gap in the current clinical knowledge. Most importantly, a significant gap exists in the management of patients with borderline left ventricular structures development in regards to optimal choice between single and biventricular repair. An additional a significant gap relates to the lack of available data describing the relationship between the choice of a management strategy, subsequent clinical course of patients in that management pathway and the long term functional outcomes and health-related quality of life.


Figure 1
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  		Fig. 1. Treatment algorithm for neonates and infants with critical left ventricular outflow tract obstruction.

 
Numerous large multi-institutional short and long-term studies are needed in order to address these significant knowledge gaps and guide the optimal management of those complex patients.


   References
Top
 Abstract
 1. Introduction
 2. Pathophysiology and clinical...
 3. Treatment
 4. Summary
 References
 

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S. C. Brown, D. Boshoff, B. Eyskens, and M. Gewillig
Hybrid approach as bridge to biventricular repair in a neonate with critical aortic stenosis and borderline left ventricle
Eur. J. Cardiothorac. Surg., June 1, 2009; 35(6): 1080 - 1082.
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