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Ann Thorac Surg 1998;66:673-677
© 1998 The Society of Thoracic Surgeons
ventricular repair
a Department of Paediatrics, Imperial College School of Medicine at National Heart and Lung Institute, London, England, United Kingdom
Address reprint requests to Prof Anderson, Paediatrics, Imperial College School of Medicine, National Heart and Lung Institute, Dovehouse St, London SW3 6LY, UK
Presented at the Workshop on "One and One-Half Ventricle Repairs," Gubbio, Italy, Dec 6–7, 1996.
Abstract
Background. The concept of "one and a half ventricular repair" relates to situations where one ventricle is capable of pumping one half of the circulation while the other ventricle is deemed inadequate and requires off-loading by means of a shunt. The inadequate ventricle is usually assigned the role of pumping the pulmonary circulation. The majority of hearts potentially amenable to this repair will have one large ventricle associated with a smaller and more-or-less rudimentary ventricle.
Methods. In this review, we focused on hearts in which the morphologically left ventricle will continue to support the systemic circulation.
Results. Among the hearts with univentricular atrioventricular connections, a few cases of classic tricuspid atresia and cases of double-inlet left ventricle coexisting with concordant ventriculoarterial connections would be suitable for incorporating the right ventricle into the pulmonary circulation. This procedure may be feasible in some cases of straddling and overriding tricuspid valve. Hearts with pulmonary atresia and intact ventricular septum display a wide range of sizes of the right ventricular cavity. Although biventricular repair is an option for those with good-sized cavities, patients with hypoplastic right ventricles may be candidates for one and a half ventricular repair.
Conclusions. For the lesions reviewed, and many others, one and a half ventricular repair can be an option.
The mechanisms underscoring the concept of "one and a half ventricular" repair are those in which one ventricle is deemed capable of pumping one half of the circulation, while the capacity of the other ventricle to pump the other half of the circulation is called into question. If, however, part of the work of the substandard ventricle is off-loaded by a shunt, then the ventricle may well be capable of pumping the part of the circulation that remains ventricular dependent. These circumstances, those of unloading part of the circulation and leaving the remainder ventricular dependent, exist only in the setting of the pulmonary circulation, because it is exceedingly unlikely that half a ventricle could support even part of the systemic circulation, even if it proved possible to unload part of this systemic circuit. When considering the anatomic substrates for this form of repair, therefore, we are concerned most of the time with a substandard right ventricle pumping into the pulmonary circulation. This anatomic situation exists when the right ventricle is incomplete and rudimentary in the setting of univentricular atrioventricular connection to a dominant left ventricle, when the right ventricle is rudimentary to a greater or lesser extent because of overriding of the right atrioventricular junction, and when the right ventricle possesses a hypoplastic cavity because of muscular mural hypertrophy in the setting of pulmonary atresia with an intact ventricular septum. The option also exists, when the ventriculoarterial connections are discordant, for the small morphologically left ventricle to be incorporated in the pulmonary circulation subsequent to off-loading part of the volume by means of an adjunctive Glenn or cavopulmonary anastomosis. This situation exists, for example, in complete transposition with ventricular imbalance. The left ventricle in such circumstances can be incorporated into the pulmonary circulation by means of an apicopulmonary conduit. This is likely to be a rare occurrence so, in this discussion, attention will be focused on those hearts in which the morphologically left ventricle continues to serve a systemic role.
Univentricular connection to a dominant left ventricle
The situation in which the rudimentary right ventricle supports the pulmonary trunk in the setting of univentricular connection to a dominant left ventricle is seen most frequently in the setting of tricuspid atresia with concordant ventriculoarterial connections [1]. This is the entity, of course, that provided the morphologic substrate for the initial Fontan procedure. One of the earliest modifications of the Fontan approach was the attempt to incorporate the rudimentary and incomplete right ventricle into the pulmonary circulation. The right ventricle in this setting is itself not only rudimentary but also incomplete, because it lacks totally its inlet component (Fig 1), so the so-called Björk modification of the Fontan procedure (Fig 2) is, perhaps, the prototype of the one and a half ventricular repair. Although proposed by Björk and associates [2] and introduced independently by Kreutzer and colleagues working in Buenos Aires [3], the first group to use this approach may have been Henry and colleagues [4] at the Mayo Clinic.
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Straddling and overriding tricuspid valve
As we have already discussed, the right ventricle is more-or-less rudimentary in the presence of straddling tricuspid valve depending on the proportion of the overriding atrioventricular junction that is connected to the dominant left ventricle. Some have taken the stance that the mere presence of a straddling tricuspid valve is an indication for the Fontan procedure. The straddling valve is then excluded entirely from the circulation by means of closure combined with atriopulmonary connection, or alternatively by construction of a total cavopulmonary connection. When the overriding orifice is only minimally connected to the dominant left ventricle, however, more recently there has been a renaissance of interest in biventricular repair [6, 7]. Between these extremes, it remains the case that certain examples of straddling and overriding tricuspid valve will provide another substrate for one-and-a half ventricular repair. Thus, when the overriding orifice is committed approximately equally between the ventricles, the incomplete right ventricle is usually markedly hypoplastic, calling into question its ability to support the entirety of the pulmonary circulation (Fig 4). The option must remain in this setting to close off that portion of the straddling valve connected to the dominant left ventricle, and to contemplate unloading part of the pulmonary circulation by means of a Glenn anastomosis. If this option is considered then it is, of course, essential to take into account the anomalous course of the conduction axis [8] when closing the ventricular septal defect (Fig 5).
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Considering the relative simplicity of the anatomic arrangement, it is perhaps surprising that overall surgical results for this lesion remain relatively poor [9, 10]. Examples of the lesion with an imperforate pulmonary valve show a good-sized right ventricular cavity, which is made up of all three of its component parts. Patients with this anatomic arrangement are candidates for either biventricular surgical repair [11] or repair by means of laser perforation of the imperforate valve and balloon dilation via interventional cardiology [12]. At the other end of the spectrum, hearts are found with muscular atresia of the subpulmonary infundibulum and muscular overgrowth of the apical trabecular component. In these patients, the ventricular cavity is, effectively, represented only by its hypoplastic inlet. At best, these are candidates only for a Fontan procedure [11]. In this group, it is the presence of complicating lesions such as fistulous communications with the coronary arteries, leading to a right ventricular-dependent coronary arterial circulation, which explains in part the dismal prognosis.
There remain a group of hearts, nonetheless, that are in a grey area between those that present themselves for either biventricular or univentricular surgical repair. These are the hearts in which there is some degree of muscular overgrowth of the apical trabecular component, together with muscular obstruction of the patent subpulmonary infundibulum. Only a small patent channel leads to a small imperforate pulmonary valve (Fig 6). It must remain questionable whether such right ventricles will be capable of supporting the pulmonary circulation after enlargement of the narrowed subpulmonary infundibulum. Success has been reported recently in such cases after biventricular repair combined with surgical overhaul of the compromised right ventricular apical trabecular component [13]. These cases, with obvious compromise of the right ventricular cavity by mural overgrowth, provide another anatomic substrate for one-and-a-half ventricular repair. They also emphasize the fact that, in pulmonary atresia with intact ventricular septum, all three constituent ventricular components are always present, but the cavity hypoplasia is produced by muscular overgrowth. Thus, it should not be inferred that the tripartite approach to analysis implies absence of one or more of the ventricular components [14]. This is far from the case. When mural hypertrophy is observed, it involves initially the apical trabecular component, and then the outlet component. This leaves, in the hearts most severely affected, only the inlet of the ventricle as effective cavity. Analysis of all hearts, nonetheless, shows evidence of the three components found in all normally constructed ventricles [15]. Within this spectrum (see Fig 6), it is those hearts with medium to severe overgrowth of the apical trabecular component, but with retention of the cavity of the infundibulum in potential communication with the cavity of the pulmonary trunk, that lend themselves to possible surgical repair with a one and a half ventricular option.
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Only a small series of congenitally malformed hearts will prove suitable for repair using the one and a half ventricular option. These are the hearts in which the morphologically right ventricle, hypoplastic to varying degree, supports the pulmonary trunk. The lesions producing the anatomy are selected examples of univentricular atrioventricular connection to a dominant left ventricle with concordant ventriculoarterial connections, straddling tricuspid valve, and pulmonary atresia with intact ventricular septum.
Acknowledgments
This work was supported by the British Heart Foundation.
References
This article has been cited by other articles:
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  A. Ansari, D. Goltz, K. P. McCarthy, A. Cook, and S. Y. Ho The conduction system in hearts with pulmonary atresia and intact ventricular septum Ann. Thorac. Surg., May 1, 2003; 75(5): 1502 - 1505. [Abstract] [Full Text] [PDF]
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 P. E. F. Daubeney, D. J. Delany, R. H. Anderson, G. G. S. Sandor, Z. Slavik, B. R. Keeton, S. A. Webber, and for the United Kingdom and Ireland Collaborative S Pulmonary atresia with intact ventricular septum: Range of morphology in a population-based study J. Am. Coll. Cardiol., May 15, 2002; 39(10): 1670 - 1679. [Abstract] [Full Text] [PDF]
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C. Mavroudis, C. L. Backer, L. M. Kohr, B. J. Deal, J. Stinios, A. J. Muster, and D. F. Wax Bidirectional Glenn shunt in association with congenital heart repairs: the 1 1/2 ventricular repair Ann. Thorac. Surg., September 1, 1999; 68(3): 976 - 981. [Abstract] [Full Text] [PDF]
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R. H. Anderson and S. Y. Ho Which hearts are unsuitable for biventricular correction? Ann. Thorac. Surg., August 1, 1998; 66(2): 621 - 626. [Abstract] [Full Text] [PDF]
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