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Ann Thorac Surg 1995;59:940-941
© 1995 The Society of Thoracic Surgeons
Cardiothoracic Unit Great Ormond Street Hospital for Children Great Ormond St London WC1N 3JH United Kingdom
Waldman and collaborators describe a thoughtful way to investigate patients with pulmonary atresia, intact ventricular septum, and important RV-CACs. They deduce a management protocol based on surgical closure of the tricuspid valve in those patients with large RV-CACs without stenosis of the native coronary arteries.
As so often happens, this article throws some light on the management of a difficult subset of patients and at the same time adds to the confusion that has surrounded those patients for many years.
The reasons for the controversy are at least threefold. First, the spectrum of anomalies seen varies from institution to institution and appears to fit in with each management protocol. Could this reflect a lack of objective criteria in the preoperative assessment of the patients? Second, the controversy results from the difficulties in assessing the actual impact of a new therapeutic procedure in the management of a very dismal condition. Interpretation bias? Third, the attraction of physiologically based management protocols sometimes can lead to the elaboration of theories not necessarily supported by the data observed and the results obtained. Intellectual vagabondage? We have fallen into the trap more than once.
I would make three specific comments on the article: (1) The balloon-tip closure of the tricuspid valve and the surgical patch closure of the tricuspid valve are, in my view, two different procedures. The former prevents desaturated blood from entering the right ventricle and, consequently, the systolic right-to-left shunt in the coronary circulation. It also suppresses the diastolic steal by right ventricular cavity obliteration. The latter procedure deals only with the first facet of the problem. The abolition of diastolic steal has not been demonstrated. One could argue that a ``Fontan'' operation, allowing the left atrial blood to ``perfuse'' the right ventricle, is better than a patch closure of the tricuspid valve. Should the abolition of the diastolic steal be deemed important, right ventricular thromboexclusion could be considered. This could be done by interventional catheterization, delivering an occlusive device in the right ventricle [1].
(2) I would hesitate to compare patients after tricuspid valve closure and patients with tricuspid atresia. The presence of a severely hypertrophied and hypertensive right ventricle interferes with left ventricular function. It does not allow the left ventricle to take the globulous shape of a compliant ventricular chamber subjected, for example, to an increased volume load after a shunt procedure. This is well seen on two-dimensional echocardiogram. It is my experience indeed that the mortality after a neonatal shunt in patients with pulmonary atresia and intact ventricular septum (without RV-CACs) is significantly higher than in patients with tricuspid atresia.
(3) The heuristic value of flow charts is not disputed. They sometimes suffer, however, from over-simplification. There is recent literature that supports convincingly the wisdom of incorporating small ventricles to create the so-called one-and-a-half--ventricle circulation, something between the biventricular and the Fontan heart. Large and discrete RV-CACs without stenosis of the native coronary arteries sometimes can be simply ligated. Infants with a right ventricular-dependent coronary circulation can present with myocardial ischemia in early infancy and be unlikely to survive until the Fontan operation. Cardiac transplantation has been suggested for these patients. In 1983, one of my residents, Dr James Sink, had the idea of interposing a valveless conduit between the aorta and right ventricle for that subset of patients. I demonstrated that such a procedure could actually equilibrate the systolic and the diastolic pressures in the right ventricle and the aorta, thus using the right ventricle as a conduit to perfuse the distal coronary arteries [1]. One of my sins of intellectual vagabondage?
Reference
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