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Biventricular repair in the management of hypoplastic left heart syndrome

Published online by Cambridge University Press:  21 September 2005

Victor O. Morell,
James A. Quintessenza and
Jeffrey P. Jacobs
Victor O. Morell
Affiliation:
Congenital Heart Institute of Florida, University of South Florida College of Medicine, Tampa Children's Hospital, All Children's Hospital, Tampa and Saint Petersburg, Florida, USA
James A. Quintessenza
Affiliation:
Congenital Heart Institute of Florida, University of South Florida College of Medicine, Tampa Children's Hospital, All Children's Hospital, Tampa and Saint Petersburg, Florida, USA
Jeffrey P. Jacobs
Affiliation:
Congenital Heart Institute of Florida, University of South Florida College of Medicine, Tampa Children's Hospital, All Children's Hospital, Tampa and Saint Petersburg, Florida, USA
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Extract

Hypoplastic left heart syndrome is the term introduced by Noonan and Nadas1 to describe a spectrum of cardiac anomalies characterized by varying degrees of significant underdevelopment of the left heart and aortic arch. These cardiac anomalies include mitral valvar disease, left ventricular hypoplasia, aortic stenosis at subvalvar, valvar, and supravalvar levels, hypoplasia of the ascending aorta and aortic arch, and aortic coarctation. Although descriptive, hypoplastic left heart syndrome suffers from being a very unspecific term, since it encompasses multiple degrees and combinations of abnormalities involving the left sided structures. In an attempt to provide gradings of severity, Kirklin and Barratt-Boyes2 categorized these patients falling into the syndrome into four classes, according to whether obstruction was found at one, two, or more levels, or whether there is aortic atresia. Then, in 1998, Tchervenkov and colleagues3 introduced the term hypoplastic left heart complex to describe a set of patients falling within the spectrum of hypoplasia of the left heart, but in the absence of intrinsic aortic or mitral valvar stenosis, this concept subsequently being endorsed by the International Committee established by the Society of Thoracic Surgeons, together with the European Association of Cardiothoracic Surgery, to rationalize the approach to nomenclature and databases.4 The analysis offered by Tchervenkov et al.3 showed that, in certain circumstances, there are potentially patients considered to have hypoplasia of the left heart who might be candidates for biventricular repair. If this is the case, then it is important to establish how this subset can be recognized, and how they are best treated.

Information

Type
Biventricular Repair
Information
Cardiology in the Young , Volume 14 , Issue S1 , February 2004, pp. 101 - 104
Copyright
© 2004 Cambridge University Press

Options for surgical management

The surgical management of patients having hypoplasia of the left-sided structures includes multistage surgical reconstruction aiming to create a functionally univentricular circulation, transplantation, and biventricular repair. Most institutions tend to use the first two options, either alone or in combination. Biventricular repair, although occasionally used, is probably underutilized because of the lack of clear guidelines for appropriate selection of the patients who might gain from this strategy of management.

Criterions for selections

Several groups have attempted to delineate specific anatomical and physiological parameters that will help identify those patients capable of undergoing biventricular repair. In 1991, Rhodes and colleagues5 analysed retrospectively the features that predicted survival in neonates and infants with critical aortic stenosis. They concluded that the adverse effects of hypoplasia of the inflow, outflow, and left ventricular cavity are cumulative. They formulated an equation:

in which BSA is the body surface area, ROOTi is the indexed dimension of the aortic root, LAR is the ratio of the dimension of the left ventricle in its long axis to the long axis dimension of the heart, and MVAi is the indexed area of the mitral valve. In their retrospective analysis, a score of less than −0.35 was predictive of death after biventricular repair. The only absolute independent parameters that were predictive of death after biventricular repair, however, were a mitral valvar area of less than 3.1 cm2/m2 and an index of left ventricular mass of less than 35 g/m2.

Subsequent to this analysis, Gundry and Behrendt6 argued that, in patients undergoing surgical valvotomy for critical aortic stenosis within the first six months of life, the presence of preoperative low ejection fraction, high left ventricular end-diastolic pressure, and endocardial fibroelastosis were all predictors of a poor outcome. Parsons and associates,7 evaluating a similar group of patients, were then able to show that the critical size for survival after valvotomy was a left ventricular cross-sectional area of greater than 2 cm2 as measured on the parasternal long axis echocardiogram. In this analysis, left ventricular end-diastolic dimension greater than 13 mm was another predictor of survival. Hammon et al.8 had found that none of their patients undergoing surgical valvotomy for critical aortic stenosis in the first six months of life had survived when the left ventricular end-diastolic volume was 20 ml/m2 or less.

Others had noticed, nonetheless, that even though the left ventricle may not be apex-forming, it may have potential for postnatal growth.9 Thus, Tani and colleagues10 reported their experience in 20 neonates with hypoplasia of the left heart and obstruction of the aortic arch who underwent successful biventricular repair. There was no mortality, despite the fact that all the patients had scores calculated using the equation of Rhodes and colleagues5 that would have predicted the need for univentricular repair. All patients, significantly, had antegrade flow in the ascending aorta, and small but non-stenotic aortic valves. Their study, therefore, demonstrates that biventricular surgical repair can be achieved in neonates with obstruction of the aortic arch, and hypoplasia of the left heart, with minimal mortality and excellent late functional results when the aortic valve is small but not intrinsically stenotic. Tani and colleagues10 also emphasized that the echocardiographic measurements used by investigation such as Rhodes and colleagues5 to predict the need for a univentricular repair in the setting of critical aortic stenosis were unlikely to be valid for the neonate with obstruction of the aortic arch.

Alboliras and colleagues11 had also reported experience in patients with severe aortic coarctation, in the setting of hypoplasia of the left ventricle, who underwent repair of the coarctation as a primary procedure. All were alive and well after the initial surgery. They observed progressive increases in the diameters of the aortic and mitral valves, and in the left ventricular dimensions, areas, and volumes. They concluded that “despite severe left ventricular hypoplasia, a two-ventricle repair is possible in selected cases”.

This experience was further endorsed by Serraff et al.,12 who had also performed primary repair in neonates with aortic coarctation and hypoplastic but morphologically normal left ventricles. In their patients, there was antegrade flow in the ascending aorta, but either right-to-left or bi-directional ductal flow. In their cohort, at 5 years, the actuarial survival, and freedom from reoperation, were 72.5% and 46%, respectively.

It is Tchervenkov and colleagues13 who have extended these experiences by proposing the introduction of the so-called hypoplastic left heart complex. Their criterions for biventricular repair included antegrade flow through the heart into the ascending aorta and the proximal branches of the aortic arch, no intrinsic stenosis of the aortic or mitral valves, adequate left ventricular function, and no endocardial fibroelastosis. Their surgical principles, and results, have been summarized in the previous review (see pp 97–100).

There are then still further subgroups of patients closely related to those having hypoplastic left heart syndrome that are potential candidates for biventricular repair. These are the ones with critical aortic stenosis, or aortic atresia with a well-developed left ventricle and a ventricular septal defect. It was Yasui et al.14 who, in 1987, described the repair for those with a ventricular septal defect. It consists of establishing continuity between the proximal pulmonary trunk and the aorta, baffling blood from the ventricular septal defect into the neoaorta, and placing a conduit from the right ventricle to the pulmonary arteries. The procedure has become known as the Norwood/Rastelli combination. This combination of maneuvers has also been performed in stages, with the Norwood procedure carried out during the neonatal period, followed by a Rastelli repair at a later time.15 All six patients reported by Pearl and colleagues15 and treated in this fashion had severe obstruction of the left ventricular outflow tract or aortic atresia, a ventricular septal defect, and an apex-forming left ventricle. All their patients survived the two-stage approach.

It is the Congenital Heart Surgeons' Society,16 however, that has organized the largest multi-institutional study looking at the management, outcomes, and risk factors of neonates with critical aortic stenosis. Their analysis included patients managed by an initial intended biventricular repair, or those treated with the Norwood procedure. They were able to develop a multiple linear regression equation that predicted both the magnitude and the direction of the benefit for survival at 5 years for those placed on the optimal pathway. In their analysis, a positive number favors the functionally univentricular approach, while a negative number favors the biventricular route. The predicted difference in proportioned survival is represented by the magnitude of the number.

Independent factors associated with an increased benefit for survival with functionally univentricular repair included younger age at entry, lower Z-scores for the aortic valve and left ventricular length, higher grades of endocardial fibroelastosis, absence of important tricuspid regurgitation, and a larger ascending aorta. On the other hand, factors associated with greater benefit for survival after attempted biventricular repair included a higher Z-score for the aortic valvar orificial diameter, a higher echocardiographic peak instantaneous gradient across the left ventricular outflow tract, a higher Z-score for the annular diameter of the mitral valve, and the absence of aortic coarctation. They reported survivals at 5 years of 70%, and 60%, for biventricular repair and the Norwood approach, respectively. Of interest, using their formula, the predicted benefit in survival favored the Norwood procedure in half of the patients who had undergone a biventricular repair, and it favored biventricular repair in one-fifth of patients who had been placed on the Norwood cascade.

Conclusions

It is clear that the surgical interventions necessary to achieve a biventricular repair in patients with hypoplastic left heart syndrome or related lesions are varied, and that the major determining factor for success is the anatomic substrate. The surgical principles delineated by others, and summarized by Tchervenkov,13 are important in achieving excellent short and long-term results. Elimination of all obstructive extracardiac lesions may require repair of an interrupted aortic arch, augmentation of a hypoplastic arch, or relief of aortic coarctation. If the aortic valve is critically stenotic, then balloon or surgical valvotomy would be indicated. With severe obstruction of the left ventricular outflow, a Ross/Konno procedure might be required, or the so-called Norwood–Rastelli procedure used if a ventricular septal defect is part of the malformation. Atrial septal defects should be closed to assure full preload of the left ventricle, and ventricular septal defects, if present, should be repaired. The concept of leaving a small patent oval foramen to “unload” the marginal left ventricle remains controversial. If endocardial fibroelastosis is identified, it can be resected to increase the dimensions of the left ventricle. Management of mitral stenosis remains a problematic area, especially for those with a small annulus.

For each individual structure in the complex of the left heart and aortic arch, a critical size must exist that limits the ability of the cardiac pump to maintain a biventricular physiology. Despite all the published reports, however, as yet there is no consensus concerning these critical sizes. It is the small number of patients treated thus far, and the lack of homogeneity in the different populations studied, that creates conflict. Despite these caveats, some generalizations can be made. Positive physiological and anatomical characteristics for biventricular repair include a morphologically normal mitral valve, even if hypoplastic, normal left ventricular function, lack of left ventricular endocardial fibroelastosis, and antegrade flow in the ascending aorta and its proximal branches. Negative characteristics include a morphologically abnormal and stenotic mitral valve, depressed left ventricular function, and the presence of endocardial fibroelastosis. It is, however, the equation permitting calculation of the benefit of survival created by the Congenital Heart Surgeons' Society that may prove to be the most useful tool when evaluating patients for initial surgical intervention.

Although the attractiveness of a biventricular repair for any type of congenital heart defect is undeniable, this strategy has to be used cautiously in patients with hypoplastic left heart syndrome. Those patients who fall within the suggested hypoplastic left heart complex, and those with aortic atresia, a ventricular septal defect and an apex-forming left ventricle are certainly potential candidates. But experience reported thus far shows that the mortality rate, and the incidence of reoperations, are far from negligible. The more liberal use of the Ross/Konno procedure to relieve obstruction in the left ventricular outflow tract in this population may prove to be advantageous, but presently there is little data to support such a radical surgical approach.

In our opinion, patients should be considered for biventricular repair when they have

  • hypoplastic left heart complex;
  • critical aortic stenosis with left ventricular hypoplasia;
  • aortic atresia with ventricular septal defect.

At the Congenital Heart Institute of Florida, the largest program performing congenital cardiac surgery in Florida, we have had success with biventricular repair in all three of these groups. But we remain selective in choosing the patients to undergo biventricular repair. Not surprisingly, the majority of our patients with hypoplastic left heart syndrome are treated either with Norwood palliation or cardiac transplantation, with staged palliation representing the most common approach, and cardiac transplantation selectively utilized in cases of where the family express this preference, or there are contraindications to the staged palliative approach. It is only a small minority of patients that is suitable for attempted biventricular repair utilizing the guidelines discussed in this review.

References

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