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Ann Thorac Surg 1998;66:641-643
© 1998 The Society of Thoracic Surgeons
a Divisions of Cardiology, Department of Pediatrics, the Hospital for Sick Children, University of Toronto Faculty of Medicine, Toronto, Ontario, Canada
b Division of Cardiovascular Surgery, Department of Surgery, The Hospital for Sick Children, University of Toronto Faculty of Medicine, Toronto, Ontario, Canada
Address reprint requests to Dr Freedom, The Hospital for Sick Children, Rm 1503C, 555 University Ave, Toronto, ON, Canada M5G 1X8
Presented at the Workshop on "One and One-Half Ventricle Repairs," Gubbio, Italy, Dec 6–7, 1996.
Abstract
Many hearts, although considered morphologically biventricular, may not be candidates for a biventricular repair. Such patients are best placed on a Fontan algorithm. This article reviews in broad principles those hearts that, despite being biventricular, do not lend themselves to a two-ventricle repair.
The introduction in 1971 of atriopulmonary connection with atrial separation as initially applied to patients with tricuspid atresia by Fontan and Baudet [1] has now been extended to a wide variety of congenitally malformed hearts [2–12]. Some of these hearts are unequivocally biventricular, but others either because of ventricular underdevelopment or some other confounding feature do not lend themselves to a standard biventricular repair. Some may be afforded long-term palliation with the Fontan operation, whereas others will be amenable to a one and a half ventricle repair. This article will review the spectrum of biventricular hearts not amenable to a biventricular repair.
Volumetric analyses
This is not the appropriate forum to discuss the role of volumetric analysis. There are, however, considerable data to support the view that angiocardiographic-derived volumetric analyses have been adequately validated with casts of normal hearts [13, 14]. Some hearts because of peculiar shape and poorly defined endocardium are less amenable to volumetric analysis. Furthermore, volumetric analyses do not address the issue of compliance, nor do they represent component hypoplasia.
The ventricle as a tripartite structure
There remains disagreement whether the morphologically right ventricle is a bipartite structure comprising a sinus portion and an outlet or infundibular portion, or whether it can be considered tripartite, with confluent inlet, apical trabecular, and outlet zones. Although this issue remains contentious, we support the positions advocated by Goor and Anderson and their respective colleagues that the ventricle can be viewed as tripartite [15, 16]. There are a number of congenitally malformed hearts that lend support to this view, including those with isolated right ventricular hypoplasia, the divided right ventricle, imperforate Ebstein’s malformation, and hearts exhibiting pulmonary atresia and intact ventricular septum [15, 17, 18].
Isolated right ventricular hypoplasia
Among some congenitally malformed hearts, the most conspicuous finding is some degree of hypoplasia of the inlet and trabecular components of the morphologically right ventricle. Such malformed hearts have been designated as having congenital right ventricular hypoplasia or isolated right ventricular hypoplasia [18–24]. This usually occurs in isolation, but right ventricular hypoplasia has been identified in patients with ventricular septal defect (VSD), atrioventricular septal defect, tetralogy of Fallot, transposition of the great arteries with large VSD, or similar conditions. For those patients with severe congenital right ventricular hypoplasia in isolation, it is unlikely that a standard biventricular repair can be accomplished, but most such patients can be treated with a one and a half ventricle repair with or without atrial fenestration [23]. A similar approach can be extended to patients with right ventricular hypoplasia complicating VSD, atrioventricular septal defect, tetralogy of Fallot, and the complex forms of transposition of the great arteries.
The hypoplastic left heart syndrome
Many hearts with typical hypoplastic left heart syndrome are typically biventricular with a grossly disordered left ventricular inlet and aortic outflow tract, with severe left ventricular hypoplasia. Even when the mitral valve is functionally atretic, the valve is usually imperforate. Thus, despite a biventricular heart, the profound left ventricular hypoplasia does not lend itself to a biventricular repair. When a conventional operation is considered, such patients are candidates for the Norwood–hemi-Fontan–Fontan algorithm.
Critical aortic stenosis
Among any cohort of newborns or neonates with critical aortic stenosis, there will be some whose cardiac dimensions approach the hypoplastic left heart syndrome. The clinical conundrum is to identify those patients whose cardiac anatomy and dimensions will allow a biventricular repair despite relative hypoplasia of left heart structures or those best placed on a Norwood–hemi-Fontan–Fontan track. To attempt to define those morphologic and dimensional variables, Rhodes and colleagues [25] performed a retrospective analysis and derived a score based on these variables. These data and data from many institutions demonstrated clearly that some patients despite an unequivocally biventricular heart were best considered for a one ventricle repair. Indeed, data from this study indicated that patients who did poorly after aortic valvulotomy also died or did poorly after conversion to a Norwood approach [25].
Double-outlet right ventricle with remote ventricular septal defect
In the majority of hearts with double-outlet right ventricle, the ventricular septal defect is spatially related to either the aortic outflow tract or to the pulmonary outflow tract by virtue of attachment of the infundibular septum to either the anterior or posterior limb of the trabecular septum. Less commonly, despite both ventricles of normal size, the VSD is remote from either arterial outlet [26–29]. Thus the patient with double-outlet right ventricle and a midtrabecular, apical, or muscular inlet VSD is perhaps better served by a one-ventricle or Fontan repair. Although it may be possible to define an intraventricular tunnel, much of the morphologically right ventricle could be compromised, but some patients could be treated with a one and a half ventricle repair. Thus, this form of double-outlet right ventricle is characterized by virtually normal-sized ventricles not amenable to a biventricular repair. A very similar situation may be seen in some patients with transposition of the great arteries, a VSD, and left ventricular outflow tract obstruction where the VSD is remote from the outlet, or where contiguous atrioventricular valve tissue crowds the VSD and makes either the classic Rastelli approach or the "REV" approach of LeCompte untenable.
Pulmonary atresia and intact ventricular septum
Among any sizeable cohort of patients with pulmonary atresia and intact ventricular septum, the coronary circulation may be wholly or in large part right ventricular-dependent [17]. These patients cannot be treated with a standard biventricular repair because any maneuver to reduce the right ventricular systolic driving pressure or volume of blood entering the right ventricle will unmask the right ventricular-dependency of the coronary circulation. In the majority of patients with pulmonary atresia and intact ventricular septum and a right ventricular-dependent coronary circulation, the tricuspid valve is very small and the right ventricle grossly underdeveloped. But this is not invariably so. Rarely, a profoundly disordered coronary circulation will be defined in a patient with pulmonary atresia and intact ventricular septum and a nearly normal-sized right ventricle.
There are other patients with disorders with a normal coronary circulation, but in whom the tricuspid Z value is -3.5 to -4.5 and all components of the right ventricle are poorly invested. Data provided by the Congenital Heart Surgeons Study indicate that it is very unlikely that such a right ventricle can be incorporated into a biventricular repair, although some patients may be candidates for a one and a half ventricle repair [30].
Hearts with an imperforate atrioventricular valve
A wide range of congenitally malformed hearts have been described with either an imperforate tricuspid or mitral valve. Such hearts should be considered biventricular, although in reality, patients with these forms of hearts should be treated by a Fontan algorithm.
Hearts with crossed atrioventricular connections
In most hearts with a biventricular atrioventricular connection, the atrial and ventricular inlet septa are aligned in a single plane, and the two bloodstreams from the atria down to the ventricular apices are parallel as seen in the four-chamber cross-sectional echocardiogram and angiocardiogram. Some hearts, however, have a varying degree of atrial septal malalignment with a loss of normal parallel connection axes [12]. Externally, these hearts are characterized by an unexpected spatial relationship of the cardiac chambers and great arteries for the given segmental connection. Internally, the bloodflow tracts from the atria down to the ventricular apices spiral around each other, and the atrial and ventricular septa show an angulated or curved configuration. Thus the heart appears twisted along its base-to-apex axis, the spatial orientation of the cardiac chambers and great arteries being governed by the degree of twisting and also by the presence of the frequently found ventricular hypoplasia. In those hearts with a greater degree of twisting, each atrium is connected to the contralateral ventricle, and the two atrioventricular blood streams "criss-cross," actually spiralling almost 180 degrees to each other. Frequently, the ventricles are arranged in a superoinferior or "upstairs-downstairs" fashion, and the ventricular septum tends to be horizontal. The twisting occurs in either a clockwise or counterclockwise direction. Usually the heart with the ventricular mass exhibiting a right-hand pattern (D-ventricular loop) is twisted in a clockwise direction, whereas the heart with a ventricular mass of an L-loop configuration is twisted in a counterclockwise direction. The common directions of twisting place the right ventricular inlet superior and anterior to the inlet of the morphologically left ventricle. Very rarely, the heart appears twisted in a direction opposite to that seen in most hearts with a twisted atrioventricular connection, with the right ventricular inlet inferior and posterior to the left ventricular inlet. In some patients with crossed atrioventricular connections, a biventricular repair is possible, but others are better served by a one-ventricle repair.
Hearts with superoinferior ventricles
The topography of the ventricular mass relative to the interventricular septum departs from normal in a number of situations. The most readily appreciated conditions for this departure are observed in patients with dextrocardia with and without situs inversus atrioventricular discordance [8]. In hearts with atrioventricular discordance, the ventricular mass is often aligned about a ventricular septum occupying a more vertical disposition than normal. In other patients the ventricular mass may be oriented about a horizontal ventricular septum [15–26]. The horizontal ventricular septum in these hearts produces the matrix for superoinferior ventricles. This is a postcardiac looping rotational anomaly. The superiorly positioned ventricle is the morphologically right ventricle and the inferiorly positioned ventricle is the left ventricle. This unusual spatial relationship between ventricles does not lend itself readily to the prediction of the type of atrioventricular connection when the atria are lateralized, ie, a concordant or discordant atrioventricular connection. In many hearts with superoinferior ventricular relationship, the superiorly positioned right ventricle is grossly hypoplastic. Depending on the type of atrioventricular connection and ventriculoarterial connection, some patients will best be treated with a Fontan algorithm, whereas others will be candidates for either a biventricular or a one and a half ventricle repair [31].
Straddling atrioventricular valve
Patients with major straddling of either one or both atrioventricular valves have been considered best placed on a Fontan algorithm, although there is recent experience with reimplantation of the straddling atrioventricular valve.
References
This article has been cited by other articles:
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  H.G. Lim, E.A. Bacha, G.R. Marx, A. Marshall, F. Fynn-Thompson, J.E. Mayer, P. Del Nido, and F.A. Pigula Biventricular repair in patients with heterotaxy syndrome. J. Thorac. Cardiovasc. Surg., February 1, 2009; 137(2): 371 - 379.e3. [Abstract] [Full Text] [PDF]
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 M. Koh, T. Yagihara, H. Uemura, K. Kagisaki, I. Hagino, T. Ishizaka, and S. Kitamura Biventricular repair for right atrial isomerism. Ann. Thorac. Surg., May 1, 2006; 81(5): 1808 - 1816. [Abstract] [Full Text] [PDF]
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 J. M. Caffarena and J. M. Gomez-Ullate Biventricular repair of complete atrioventricular canal, double-outlet right ventricle and common atrium using a modified double switch technique. A valid alternative to univentricular procedure Interactive CardioVascular and Thoracic Surgery, June 1, 2005; 4(3): 200 - 202. [Abstract] [Full Text] [PDF]
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 E. Belli, A. Serraf, F. Lacour-Gayet, M. Hubler, J. Zoghby, L. Houyel, and C. Planche Double-outlet right ventricle with non-committed ventricular septal defect Eur. J. Cardiothorac. Surg., June 1, 1999; 15(6): 747 - 752. [Abstract] [Full Text] [PDF]
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