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Eur J Cardiothorac Surg 2005;27:67-73
© 2005 Elsevier Science NL

Review

Borderline left ventricle

Antonio F. Corno*

Department of Cardiothoracic Surgery, Alder Hey Royal Children Hospital, Liverpool, L12 2AP, UK

Received 13 August 2004; received in revised form 1 October 2004; accepted 4 October 2004.

* Tel.: +44 151 2525713; fax: +44 151 2525643. (E-mail: antonio.corno{at}rlc.nhs.uk).


   Abstract
Top
 Abstract
Introduction
 1. Introduction
 2. Aortic valve stenosis
 3. Aortic coarctation with...
 4. Hypoplastic left heart...
 5. Right ventricular pressure...
 6. Conclusions
 References
 
SUMMARY: The first problem to solve when dealing with the topic ‘borderline left ventricle’ is to find the appropriate definition. Several parameters have been taken into consideration, either morphometric (diameter of the mitral valve, indexed mitral valve area, left ventricular inflow dimension, left ventricular cross-sectional area, ratio between the apex-to-base left ventricular dimension and right ventricular dimension, left ventricular long axis to heart long axis ratio, left ventricular end diastolic volume, left ventricular mass index, ratio of the right/left ventricular wall thickness, presence of endocardial fibroelastosis, cardiac apex not formed by the left ventricle, diameter of the ventriculo-aortic junction, diameter of the aortic valve annulus and indexed aortic root diameter) as well as functional (left ventricular ejection fraction, left ventricular end diastolic pressure, mean pulmonary artery pressure, direction of the blood flow in the ascending aorta and at the level of the patent ductus arteriosus). Pre-operative determination whether the left ventricle is adequate to sustain the systemic circulation, or it may became adequate with the available surgical approaches, and therefore a bi-ventricular type of repair is feasible, can be extremely difficult, particularly in the presence of a ‘borderline left ventricle’. In the clinical practice pediatric cardiologists and cardiac surgeons are faced with the problem of the ‘borderline left ventricle’ in four different groups of congenital heart defects: (a) aortic valve stenosis, (b) aortic coarctation, with or without hypoplastic aortic arch, (c) hypoplastic left heart complex, (d) right ventricular pressure and/or volume overload. In all the above situations in the presence of a left ventricle smaller than normal a very exhaustive approach has been reviewed in the decision making process, taking in account the literature reports as well as the personal experience. In each patient with ‘borderline left ventricle’ the elements to be considered for the decision making process between uni- and bi-ventricular type of repair, or for less ideal options of management, are the following: morphometric and functional parameters, hemodynamic data, available surgical options, results of the personal and institutional experience.

Key Words: Aortic valve • Congenital heart disease • Mitral valve • Pediatric • Surgery • Ventricle


   Introduction
Top
 Abstract
 Introduction
1. Introduction
 2. Aortic valve stenosis
 3. Aortic coarctation with...
 4. Hypoplastic left heart...
 5. Right ventricular pressure...
 6. Conclusions
 References
 

"It is our choices, Harry, that show what we truly are, far more than our abilities."

Albus Dumbledore, Headmaster at Howgwarts in ‘Harry Potter and the Chamber of Secrets’ by J.K. Rowling.


   1. Introduction
Top
 Abstract
 Introduction
 1. Introduction
2. Aortic valve stenosis
 3. Aortic coarctation with...
 4. Hypoplastic left heart...
 5. Right ventricular pressure...
 6. Conclusions
 References
 
The first problem to solve when dealing with the topic ‘borderline left ventricle’ is to find the appropriate definition.

On the English Dictionary Collins [1] borderline is defined as ‘an indeterminate position between two conditions’ and also ‘on the edge of one category and verging on another’.

If these definitions were applied to the left ventricle, the ‘borderline left ventricle’ should be considered as "a ventricle with an indeterminate position between ‘normal’ and ‘small’", but also "a ventricle on the edge of the category of ‘normal’ size, but verging on ‘small’ size".

In order to give a quantitative evaluation, able to allow a scientific approach to the problem, tables with normal left ventricular dimensions and z-values, with standard deviations from the normal values, have been provided in the last edition of a book generally accepted as one of the main references in cardiac surgery, in relationship with the body surface area [2]. The same book reported as criteria to define a left ventricle as hypoplastic, therefore inadequate to sustain a bi-ventricular type of repair, the association of indexed mitral valve area <4.75cm2/m2, left ventricular inflow dimension <25mm, ratio between the apex-to-base left ventricular dimension and right ventricular dimension <0.8, and aortic annulus <6mm [2].

Despite the above criteria have been provided as guidelines, a much more exhaustive approach is needed in the decision making process for patients with a left ventricle smaller than normal. This review article is an attempt at providing the elements, derived from the literature and from the personal experience, useful to decide among the available surgical options.

In the clinical practice pediatric cardiologists and cardiac surgeons are faced with the problem of the ‘borderline left ventricle’ in four different groups of congenital heart defects with ventriculo-arterial concordance:

• aortic valve stenosis
• aortic coarctation, with or without hypoplastic aortic arch
• hypoplastic left heart complex
• right ventricular pressure and/or volume overload

Patients with ventriculo-arterial discordance have been excluded from this review.


   2. Aortic valve stenosis
Top
 Abstract
 Introduction
 1. Introduction
 2. Aortic valve stenosis
3. Aortic coarctation with...
 4. Hypoplastic left heart...
 5. Right ventricular pressure...
 6. Conclusions
 References
 
Generally the problem of ‘borderline left ventricle’ complicates the decision making process in neonates with critical aortic valve stenosis (Fig. 1).



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  		Fig. 1. (A) Echocardiographic four chamber view in a neonate with aortic valve stenosis showing the borderline size of the left ventricular cavity, with end diastolic left ventricular volume=17mL/m2 of body surface area. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. (B) Angiocardiographic lateral view in the same neonate. aAO, ascending aorta; AoS, aortic valve stenosis; LV, left ventricle.

 
The initial attempts at treating neonates and infants with severe left ventricular outflow tract obstruction have been characterized by elevated mortality in the presence of reduced left ventricular size.

In subsequent retrospective studies on the topic, several risk factors have been progressively taken in consideration and found correlated with poor results [3–17].

Left ventricular cross-sectional area <1.6cm2, measured with echocardiography, was correlated with very high mortality in infants [3].

Reduced left ventricular end diastolic volume (<80% of normal) and extensive endocardial fibroelastosis with the association of myocardial sinusoids, diagnosed angiographically, and confirmed at autopsy in six over 10 patients, were correlated with mortality in young infants presented within the first two months of life [4].

All deaths have been reported in patients who underwent aortic surgical valvotomy with an indexed left ventricular end diastolic volume <20mL/m2 of body surface area [5].

In another study, despite the suggestion to consider a uni-ventricular type of repair for infants with an indexed left ventricular end diastolic volume <20mL/m2 of body surface area, the small left ventricular size was not considered a risk factor, reporting no deaths after surgical valvotomy in four neonates with an indexed left ventricular end diastolic volume between 20 and 26mL/m2 of body surface area [6]. On the contrary, in the same study risk factors constantly associated with mortality were endocardial fibroelastosis, left ventricular end diastolic pressure >26mmHg and left ventricular ejection fraction <42% [6].

Other authors reported neonates with critical aortic stenosis who underwent either closed (trans-ventricular) or open surgical aortic valvotomy [7]. Risk factors associated with higher mortality were pre-operative clinical conditions like severe congestive heart failure with hepatomegaly, poor peripheral perfusion with metabolic acidosis (arterial pH on admission=7.3), cardiomegaly on X-ray (cardio-thoracic ratio=0.7) and right ventricular hypertrophy on electrocardiogram (as possible indication of diminished left ventricular volume or mass) [7]. While morphometric parameters associated with hospital mortality were diameter of the mitral valve <11mm and diameter of the aortic valve <6mm, functional parameters were left ventricular end diastolic pressure >20mmHg and left ventricular ejection fraction <40% [7]. Apparently this was the first time that reduced dimension of the left ventricular inflow has been recognized as risk factor for mortality in the surgical treatment of critical aortic stenosis.

No survivors have been reported in a group of infants operated on for critical aortic stenosis with indexed left ventricular end diastolic volume <20mL/m2 of body surface area, and in addition observed increased hospital mortality in patients with pre-operative mean pulmonary artery pressure >50mmHg, adding another functional parameter to the list of risk factors [8].

Increased hospital mortality was reported also in a clinical comparison between surgical aortic valvotomy and percutaneous balloon valvotomy in neonates with critical aortic stenosis in the presence of reduced left ventricular size [9]. Poor outcome accompanied small (60–80% of normal) and hypoplastic (<60% of normal) left ventricular end diastolic volume [9].

A subsequent study on neonates who underwent open surgical valvotomy for critical aortic stenosis revealed as risk factors the presence of reduced left ventricular end diastolic volume (<60% of normal) and a newly considered morphologic characteristic: the cardiac apex not formed by the left ventricle [10].

In another study, the clinical and echocardiographic data of 20 infants with critical aortic stenosis treated by open surgical valvotomy have been compared with the morphometric data obtained by 20 heart specimens from infants of the same age group [11]. From this study the risk factors associated with poor outcome resulted small mitral valve orifice <9mm, left ventricular inflow dimensions <25mm, and diameter of the ventriculo-aortic junction <5mm [11]. The authors of this study, underlining once more the importance of the dimensions of the left ventricular inflow as prognostic factor in the treatment of severe left ventricular outflow tract obstruction, suggested for this group of patients either cardiac transplantation or uni-ventricular type of repair [11].

Some of the risk factors already reported, namely left ventricular cross-sectional area <2.0cm2 and indexed left ventricular end diastolic volume <20mL/m2 of body surface area have been associated with all deaths in another study, while left ventricular end diastolic dimension <13mm was correlated with increased mortality [12]. Once again, based on the conclusion of their observations the authors suggested either cardiac transplantation or uni-ventricular type of repair as the alternative approach for infants with critical aortic stenosis and left ventricle with the above morphometric parameters [12].

A very extensive retrospective analysis has been performed by the Boston group on the echocardiographic data of infants with critical aortic stenosis, mostly treated by percutaneaous balloon dilatation of the aortic valve, and the following parameters resulted correlated with increased risk for hospital death: left ventricular long axis to heart long axis ratio <0.8, indexed aortic root diameter <3.5cm/m2 of body surface area, indexed mitral valve area <4.75cm2/m2, and left ventricular mass index <35g/m2 [13]. Based on the results of their multivariate analysis, the authors of the study proposed a score, called afterwards the ‘Score of Rhodes’, consisting in the following equation: 14.0 (BSA)+0.943 (iROOT)+4.78 (LAR)+0.157 (iMVA)–12.03, obtained by entering the data of the body surface area (BSA), the indexed aortic root dimension (iROOT), the ratio of the long axis dimension of the left ventricular to the long axis dimension of the heart (LAR), and the indexed mitral valve area (iMVA) [12]. This equation allowed prediction of death after bi-ventricular type of treatment in the presence of a discriminating Score <0.35 [13]. Few years after the publication of this article one of the co-authors (CSD) reported a misprint in the original article of the formula related to the calculation of the mitral valve area, but he ensured that, despite the formula was misprinted, the correct formula was used to obtain the reported core [14].

The attention to a morphological characteristic of the left ventricle, previously presented by another study [4], consisting in the presence of the so-called spongy myocardium, has been underlined as a harbinger of poor outcome [15]. Spongy myocardium can be easily demonstrated on angiographic investigation with left ventriculography [15].

In a clinical report of infants with critical aortic stenosis treated with bi-ventricular type of repair, either by aortic surgical valvotomy or Ross-Konno procedure, morphometric parameters associated with increased hospital mortality were the presence of endocardial fibroelastosis and cardiac apex not formed by the left ventricle, together with a negative Score of Rhodes resulting from the analysis of the left ventricular dimension [16]. This study introduced the very important concept of considering hemodynamic parameters in the decision making process, in particular the observation of the blood flow pattern in the ascending aorta and in the transverse aortic arch. In their retrospective analysis the authors found the presence of total or predominant ante-grade blood flow in the ascending aorta and transverse aortic arch correlated with survival after bi-ventricular type of repair [16].

A prospective multi-institutional clinical study was performed by the Congenital Heart Surgeon Society of North America in neonates with critical aortic stenosis in order to determine factors able to predict the best chance for survival with either a bi-ventricular or a uni-ventricular type of repair [17]. The risk factors for hospital mortality resulting from a multivariable analysis were younger age, presence and degree of endocardial fibroelastosis, left ventricular length and lower z-value of the aortic valve diameter for bi-ventricular type of repair, and presence of moderate or severe tricuspid valve regurgitation and lower diameter of the ascending aorta for uni-ventricular type of repair [17]. As a result of this study the Congenital Heart Surgeon Society of North America proposed a Critical Aortic Stenosis Calculator, consisting in a multiple variable equation (available on the net at www.chssdc.org) where after entering the demographic data of the neonate and the morphologic parameters obtained by the pre-operative echocardiographic investigation, the resulting figure predicts for the specific patient the optimal pathway (bi-ventricular or uni-ventricular type of repair) to obtain survival [17].

The main limit of the above multi-institutional study, despite the impressive amount of information and the outstanding analysis, was that in the comparison between bi-ventricular and uni-ventricular type of repair the only surgical approach taken in consideration for bi-ventricular repair was the aortic valvotomy [18]. Other surgical options available in neonates with critical aortic stenosis, like the Ross or Ross-Konno procedures, have not be taken in consideration in the above multi-institutional study, despite previous positive reports [19–23]. In fact the above study could not better recommend the Ross-Konno procedure for neonates with critical aortic stenosis. By normalizing the left ventricular outflow tract dimensions and hemodynamics, and by allowing easy access to the left ventricular myocardium for resection of the endocardial fibroelastosis, this surgical approach addresses three of the most important morphologic risk factors correlated with bi-ventricular repair: presence and degree of endocardial fibroelastosis, left ventricular length and lower z-value of the aortic valve diameter [18].


   3. Aortic coarctation with or without hypoplastic aortic arch
Top
 Abstract
 Introduction
 1. Introduction
 2. Aortic valve stenosis
 3. Aortic coarctation with...
4. Hypoplastic left heart...
 5. Right ventricular pressure...
 6. Conclusions
 References
 
Another situation where the borderline size of the left ventricle may complicate the decision making is the presence of aortic coarctation with or without hypoplasia of the aortic arch [15,24–29].

When the left ventricle is borderline, the main difference between critical aortic stenosis and aortic coarctation with or without hypoplasia of the aortic arch is the predictable growth of the left ventricle. Provided that adequate relief of the systemic obstruction at the level of the isthmus and aortic arch can be obtained with the surgical treatment, significant growth of the left ventricular dimension has been proven [24–32], even in neonates with indexed left ventricular end diastolic volume is 10mL/m2 of body surface area and cardiac apex not formed by the left ventricle [26]. Therefore the morphometric parameters like the score of Rhodes [13] should be used with caution in lesions with systemic obstructions other than critical aortic stenosis, and particularly in the presence of aortic coarctation with or without aortic arch hypoplasia [26–32].

The above observations should be discussed keeping in mind two considerations: the hemodynamic parameters and the presence of an atrial septal defect.

With regard to the hemodynamic parameters, the antegrade direction of the blood flow in the ascending aorta, and particularly the presence of bi-directional blood flow at the level of the patent ductus arteriosus characterize the left ventricle with potential for growth, and therefore suitable for bi-ventricular type of repair [30].

These neonates with hypoplastic or borderline left ventricle and aortic coarctation frequently have pre-operatively a significant left-to-right shunting at the atrial level, largely due to diastolic dysfunction secondary to the increased after-load. Generally these neonates do not need surgery for the inter-atrial communication, since the defect in most of the cases is a dilated patent foramen ovale that gets smaller in size and eventually closes spontaneously after successful repair of the aortic coarctation [33]. In these neonates the rapid increase in left ventricular size after normalization of the after-load suggest that the left ventricular hypoplasia resulted mostly from the reduced pre-load due to the left-to-right shunting at the atrial level [31].

Even when adequate growth of the left ventricular size is obtained, the early and late outcome in these neonates can be complicated by the diastolic dysfunction of the left ventricle, causing a prolonged adaptation time of the left ventricle, despite an adequate relief of the systemic obstruction. The clinical consequences are lengthy hospitalisation [29], and a late follow-up characterized by a non-compliant left ventricle, with subsequent severe left atrial hypertension and pulmonary hypertension [34].


   4. Hypoplastic left heart complex
Top
 Abstract
 Introduction
 1. Introduction
 2. Aortic valve stenosis
 3. Aortic coarctation with...
 4. Hypoplastic left heart...
5. Right ventricular pressure...
 6. Conclusions
 References
 
The nomenclature of hypoplastic left heart complex has been introduced quite recently to indicate a subset of patients at the favourable end of the spectrum of hypoplastic left heart syndrome characterized by hypoplasia of the structures of the left heart-aorta complex, consisting of aortic and mitral valve hypoplasia but without valvular stenosis or atresia, hypoplasia of the left ventricle, hypoplasia of the left ventricular outflow tract, hypoplasia of the ascending aorta and of the aortic arch, with or without aortic coarctation [35–37]. The pathophysiology in these patients is characterized by the constant presence of antegrade blood flow in the ascending aorta and in the proximal branches of the aortic arch, and the absence of left ventricular fibroelastosis.

The growth of the left ventricle in patients with hypoplastic left heart complex has been proved after bi-ventricular type of repair, provided the accomplishment of complete relief of the systemic obstruction [35–39]. The preferred surgical technique is the reconstruction of the ascending aorta and aortic arch using either a pulmonary autograft or homograft.

In this situation general agreement does not exists regarding the management of the frequently associated inter-atrial communication.

Complete elimination of the left-to-right shunt due to the presence of an atrial septal defect has been suggested to reduce the risk of low cardiac output due to excessive left-to-right shunt through an unrestrictive communication and to improve the left ventricular filling and therefore the subsequent left ventricular growth [37]. Nevertheless complete closure of the inter-atrial communication has been reported with the complications of a stormy post-operative course, with very elevated left atrial pressure particularly during the first 24–48h [35]. The elimination of left-to-right shunt at atrial level suddenly forces the entire output through the non-compliant left ventricle, resulting in left ventricular overload and distension. Since the neonatal left ventricle is already functioning at the plateau level of the Starling's curve, any volume overload can determine severe left ventricular dysfunction, and eventually death [38]. An alternative surgical option is the partial closure of the atrial septal defect: a fenestration allows a substantial reduction of the excessive left-to-right shunt in order to improve the left ventricular filling, and in the same time leaves enough time to the left ventricle to adapt to the new loading conditions [38,39].

This surgical approach has been recently utilized in our unit in a neonate with hypoplastic left heart complex with severe aortic coarctation, hypoplastic aortic arch and ascending aorta, large atrial septal defect (diameter=10mm), small mitral valve (diameter=6mm, with tricuspid valve diameter=11mm) (Fig. 2A) and small left ventricular cavity (14.5mL/cm2 of B.S.A.). Only three weeks after a first operation consisting in aortic coarctectomy through left thoracotomy, the left ventricular size increased to reach a volume of 20mL/cm2 of BSA, with mitral valve diameter=16mm and tricuspid valve diameter=20mm (Fig. 2B). Because of the severe left-to-right shunt (QP/Qs=3.3) through the atrial septal septal defect the child remained in heart failure. At cardiac catheterization laboratory a temporary balloon occlusion of the atrial septal defect was accompanied by severe elevation of the end diastolic left ventricular pressure and left atrial pressure up to 45mmHg. At this point the patient underwent, through median sternotomy and cardiopulmonary bypass, enlargement of the ascending aorta and aortic arch using an autologous patch from the pulmonary artery, with partial closure of the atrial septal defect using a PTFE patch with a central fenestration of 4mm. The post-operative course was uneventful.



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  		Fig. 2. (A) Echocardiographic four chamber view before aortic coartectomy showing the borderline size of the left ventricular cavity, with diameter of the mitral valve=6mm and diameter of the tricuspid valve=11mm. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. (B) Echocardiographic four chamber view after aortic coartectomy showing the increased size of the left ventricular cavity, with diameter of the mitral valve=16mm and diameter of the tricuspid valve=20mm. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

 

   5. Right ventricular pressure and/or volume overload
Top
 Abstract
 Introduction
 1. Introduction
 2. Aortic valve stenosis
 3. Aortic coarctation with...
 4. Hypoplastic left heart...
 5. Right ventricular pressure...
6. Conclusions
 References
 
The problem of a borderline left ventricle in the presence of right ventricular pressure and/or volume overload has been reported with several congenital heart defects, particularly total anomalous pulmonary venous connection, unbalanced atrio-ventricular septal defect, and cortriatriatum.

Clinical and pathological studies have already addressed long time ago the reduced size of the left ventricle in the presence of total anomalous pulmonary venous connection [40–44]. The left ventricular cavities with reduced size because of the leftward displacement of the inter-ventricular septum have been seen on echocardiographic and angiographic (Fig. 3) investigations [40,42,43] due to the combined pressure–volume overload of the right ventricle. Contrasting results from autopsy studies appeared in the literature, with some authors showing a reduced left ventricular size with increased right-to-left ventricular volume ratio in non-survivors after repair [43]. Other investigators observed that, because of the morphometric observation of normal size of the mitral and aortic valves, the left ventricular volume was not decreased despite changes in the ventricular shape [44]. In fact an autopsy examination confirmed the presence of left ventricles with normal mass, despite a reduced size of the aortic valve circumference, interpreted as due to the low left ventricular output probably compromised by the left to right shunt and by the septal displacement [41].



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  		Fig. 3. Angiographic lateral view in a neonate with total anomalous pulmonary venous connection and ‘borderline left ventricle’, with end diastolic left ventricular volume=14mL/m2 of body surface area. aAo, ascending aorta; dAo, descending aorta; LV, left ventricle.

 
More complex is the problem of evaluating the importance of the size of the left ventricle in patients with atrio-ventricular septal defect. A retrospective study on conventional repair showed the relationship between probability of hospital death and ventricular dominance ratio, with more than 60% mortality in children with complete atrio-ventricular septal defect for a right ventricular dominance with right/left ventricular volume=2.0, and more than 80% mortality for a right/left ventricular volume=2.5 [45]. Because of the above report, alternative surgical options have been considered in the presence of severe right ventricular dominance. The surgical approach we have proposed in the past consisted of a uni-ventricular type of repair: the first palliative stage was a pulmonary artery banding, followed by bi-directional Glenn (end-to-side superior vena cava to right pulmonary artery anastomosis) accompanied by modified Damus-Kaye-Stansel (transection of the main pulmonary artery at the bifurcation and end-to-side anastomosis to the ascending aorta) [46]. More recent clinical reports supported the feasibility of bi-ventricular repair in children with complete and partial atrio-ventricular septal defect, even in the presence of unbalanced ventricular morphology, provided that the cardiac apex is formed by the left ventricle [47–49].

An interesting approach to evaluate the suitability of bi-ventricular repair in congenital lesions with right ventricular overload associated with borderline left ventricle has been proposed by the group of San Francisco [50,51]. They hypothesized that the post-operative left ventricular capacity may be better reflected by the pre-operative potential left ventricular volume, calculated as the left ventricular volume if the septal position were normal, without the reverse bowing of the inter-ventricular septum [50,51]. The pre-operative calculation of the potential left ventricular volume is based on a theoretical model of a compressible but otherwise non-compliant left ventricular chamber; while the relative loading states of the right and left ventricle determine the position of the inter-ventricular septum, the right-to-left bowing of the inter-ventricular septum does not induce any change of the endocardial circumference nor of the left ventricular length [50,51]. The hypothesis based on the theoretical model has been confirmed in a clinical study on children with total anomalous pulmonary venous connection, unbalanced atrio-ventricular septal defect with cardiac apex not formed by the left ventricle, and cor triatriatum; the potential left ventricular volume calculated on the pre-operative echocardiographic investigation corresponded very well, or even underestimated, the post-operative left ventricular volume obtained after bi-ventricular repair [50]. Since successful bi-ventricular repair has been accomplished even in patients with pre-operative indexed left ventricular end diastolic volume <15mL/m2 of body surface area and cardiac apex not formed by the left ventricle, the authors concluded that in the presence of right ventricular pressure and/or volume overload the small pre-operative left ventricular volume is not primarily due to compression by an overloaded right ventricle, but rather to underfilling: the left ventricle is not ‘hypoplastic’, is simply ‘squashed’ [50].

These clinical observations have been confirmed by our experimental study on chronic hypoxia [52]. While the cross-sectional area of the right ventricle in animals exposed to chronic hypoxia was significantly (P<0.001) larger than in normoxic animals (control group), the cross-sectional area of the left ventricle in animals exposed to chronic hypoxia was significantly (P<0.001) smaller than in normoxic animals (control group) [52]. Even more interesting was the observation that the total cross-sectional ventricular area (right plus left ventricle) remained the same in all groups, irrespective of the changes of the separate ventricles [52], confirming that, despite volume and/or pressure overload, the heart maintains its unique morphology [53].


   6. Conclusions
Top
 Abstract
 Introduction
 1. Introduction
 2. Aortic valve stenosis
 3. Aortic coarctation with...
 4. Hypoplastic left heart...
 5. Right ventricular pressure...
 6. Conclusions
References
 
This review considers only patients with congenital heart defects with ventriculo-arterial concordance. Our experience in the presence of ventriculo-arterial discordance has been already published recently [54].

Pre-operative determination whether the left ventricle is adequate to sustain the systemic circulation, or it may became adequate with the available surgical approaches, and therefore a bi-ventricular type of repair is feasible, can be extremely difficult, particularly in the presence of a ‘borderline left ventricle’.

The elements for the decision making process between uni- and bi-ventricular type of repair are the following: morphometric and functional parameters, hemodynamic data, available surgical options, results of the personal and institutional experience.

When still in doubt, the following considerations may help in the decision making process:

– an uni-ventricular type of repair after a failed attempt at a bi-ventricular repair is associated with increased mortality [13], while the opposite seems characterized by better outcome [55]
– like for the hypoplastic right ventricle, we still don't have the answer to the question ‘Is a high-risk bi-ventricular repair always preferable to conversion to a single ventricle repair?’ [56]

As usually in the decision making process the most important consideration remains that ‘every patient is unique’ [57].


   Acknowledgments
 
Dr Stefano Di Bernardo very kindly provided most of the illustrations used for the preparation of the article.


   Footnotes
 
{star} Paper presented at the 39th Annual Meeting of the Association of European Paediatric Cardiologists, Munich, May 18–22, 2004.


   References
Top
 Abstract
 Introduction
 1. Introduction
 2. Aortic valve stenosis
 3. Aortic coarctation with...
 4. Hypoplastic left heart...
 5. Right ventricular pressure...
 6. Conclusions
 References
 

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