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J Thorac Cardiovasc Surg 1999;118:1052-1055
© 1999 Mosby, Inc.

SURGERY FOR CONGENITAL HEART DISEASE

Commentary

Brian W. McCrindle, MD, MPH, Toronto, Ontario, Canada


   Introduction
Top
 Introduction
References
 
Pulmonary atresia with intact ventricular septum (PA/IVS) is a complex lesion comprising complete obstruction of the pulmonary outflow tract, together with varying degrees of hypoplasia of the right ventricular (RV) complex, a feature it often shares in a continuum with critical pulmonary stenosis. Correlated with increasing degrees of right heart hypoplasia are the presence of aberrations of the coronary artery circulation, culminating in RV dependence of perfusion of the coronary arteries.Go Go 1-5 Management strategies involving decompression of the RV in the face of RV-dependent coronary circulation are controversialGo Go Go 1,3-9 and may impose a substantial risk of myocardial ischemia and death. However, coronary artery anomalies associated with this defect can be very complex, and accurate and precise delineation is necessary to avoid this complication.Go Go 1,5

The article by Jahangiri and associates reports contemporary results in 47 patients managed surgically from 1991 to 1998 at a single institution. This study is a small, retrospectively reviewed case series with only a descriptive analysis and a historical comparison to selected results reported in the literature. On this basis, the authors are asking us to accept two main points: that their results are markedly improved and that this improvement is based on the sole factor of a decision to initially stratify management on the basis of the presence or absence of RV-dependent coronary circulation.

Some methodologic issues prevent automatic acceptance of these points. It is difficult to refute that the survival in this series is excellent. However, a better case for improvement could have been made if they had extended their series backward in time to include patients from the era with higher mortality and had then made the appropriate statistical comparison, while adjusting for other potential associated factors that may have evolved over time. This would have allowed them to state their conclusion with confidence that they had excluded chance as a potential explanation for their results. The authors also equate "results" with mortality; no other outcomes are assessed. This is, unfortunately, a prevalent perspective presented in the surgical literature, where mortality (sometimes only operative) and reoperation are the only outcomes of apparent interest.

However, with increasing sophistication of surgical and medical management, mortality is becoming a less prominent issue, and the focus must shift toward morbidity, functional status, quality of life, and resource demands in both the short and long term. When mortality is equivalent with different strategies, these types of outcomes must then play into the decision-making. The current controversy that remains to be resolved is whether reduced morbidity and a better functional outcome can be achieved by forcing a borderline hypoplastic RV toward a biventricular repair or to abandon (single-ventricle route) or assist it (1.5-ventricle route).

The cause of these results is stated to be an initial management strategy based on the presence of RV-dependent coronary circulation, and the authors report a prevalence of RV-dependent coronary circulation of 34%, which is higher than in previous published reports.Go 2 The exact details of the coronary anatomy are not provided, in contrast to previous reports from their institution, which concluded that precise definition of the coronary artery anatomy is an essential part of the preoperative assessment.Go 1 As a result of this strategy, a higher proportion of the patients were moved away from biventricular repair, albeit with excellent intermediate survival. Initial data concerning adequacy of right heart structures are limited to the Z-value of the tricuspid valve and a subjective echocardiographic assessment of overall RV size.

Information concerning the adequacy of the inlet trabecular zone and outlet infundibulum of the RV are not provided. Although RV growth is stated to also be a determining factor, this information was not reported. Details regarding subsequent interventional catheter procedures are lacking, and these types of procedures are increasingly playing a role in initial and subsequent management.Go Go 10-12

Many factors influence mortality and suitability for biventricular versus single or 1.5-ventricle repair strategies. Precise anatomic and functional definition of the tricuspid valve,Go Go Go Go 2,6,9,13 RV,Go Go Go Go Go 3,6,7,14-16 pulmonary arteries,Go 17 left ventricle,Go Go 3,18 and coronary arteriesGo Go Go Go 1,2,5-9 is necessary, with previous reports providing evidence of these as risk factors influencing strategy and mortality. Some of these factors are also dynamically changing and may be influenced by the choice of initial management strategy.Go Go 19-23 These initial factors were best delineated in the report from the Congenital Heart Surgeons Society, which showed in a large (n = 171), multi-institutional case series that increasing hypoplasia of the tricuspid valve, severe RV-dependent coronary circulation, lower birth weight, and earlier date and type of procedure were independent risk factors associated with time-related death. In addition, on the basis of management decisions from these institutions, the only risk factor predicting completion of a biventricular repair was the Z-score of the tricuspid valve.

In the current series by Jahangiri and associates, given only 1 death over a median follow-up interval of 33 months, with many patients in an intermediate stage at the end of the study, the authors did not have the ability to look for factors associated with mortality. Also, their stated predetermined strategy based on RV-dependent coronary circulation precluded analysis of any other competing strategy. It is interesting to note that 6 patients without RV-dependent coronary circulation had only an initial systemic–pulmonary arterial shunt, with the stated reason being that the RV was judged to be inadequate. Clearly factors other than the absence of RV-dependent coronary circulation formed these decisions, and although not emphasized, adequacy of the RV judged subjectively was also incorporated into their management algorithm.

The overall limitation of this article is in the quantity and quality of the evidence provided and the potential oversimplification and implications of the conclusions. How might the authors have maximized the quantity and quality of evidence that their case series could provide? Table I lists some potential strategies.


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  		Table I. Strategies to improve the quantity and quality of evidence provided by a case series
 
Improvements in anatomic and functional assessment, management of single ventricle physiology both before and after the operation, together with innovations such as staging with a bidirectional cavopulmonary anastomosis and the potential benefits of fenestration with an interatrial communication, have greatly contributed to increasing survival in these patients. Future advancements in the care and prognostication for patients with PA/IVS will require the collaboration of surgeons, cardiologists, developmental specialists, psychologists, psychiatrists, statisticians, and others, as well as increasing collaboration between institutions.

Brian W. McCrindle, MD, MPH, Toronto, Ontario, Canada


   References
Top
 Introduction
 References
 

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