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Ann Thorac Surg 2004;78:1998
© 2004 The Society of Thoracic Surgeons
Department of Cardiac Surgery, St. George's Hospital and Medical School, Blackshaw Rd, London SW17 0QT, UK
The outcome of pulmonary atresia with an intact ventricular septum (PAIVS) remains inferior compared with other complex congenital heart defects such as transposition of the great arteries. This may reflect partly on the morphologic heterogeneity of this condition and partly on the interpretation of this morphology by different institutions.
The morphologic heterogeneity in PAIVS encompasses a spectrum of lesions, including hypoplasia of the right ventricle (RV) and tricuspid valve, abnormal coronary circulation, and pulmonary atresia itself. Ideally, surgery should optimize the growth of the RV and the tricuspid valve without compromising the coronary circulation and ventricular function. In addition, several physiologically based management protocols and algorithms are not supported by surgical outcome.
A particular challenge in planning a strategy for the treatment of PAIVS is that RV growth and contribution to pulmonary flow is difficult to predict, yet critical to the question of whether the patient will benefit from efforts to obtain a biventricular repair. Presumably, achieving a two-ventricle repair is ideal. Sometimes, attempts at RV decompression and allowing for the growth of the RV and tricuspid valve can result in high early, mid and late surgical mortality. This may be due partly to the presence of right ventricular-dependent coronary circulation.
The potential mechanisms for adverse outcome after RV decompression may be due to the RV-to-coronary fistulas without coronary stenosis, resulting in the run off from the aorta into the RV during diastole (steal phenomenon). If stenosis is present either proximal or distal to the fistula, both ischemia and steal may account for poor performance. However, potential RV steal, without coronary stenosis, does not preclude RV decompression. RV decompression is contraindicated in the presence of stenosis or occlusion of the coronary arteries. Death in patients with a right ventricular-dependent coronary circulation who undergo RV decompression is most probably related to the amount of left ventricular myocardium at risk of ischemia.
Fenton and colleagues have set out to analyze interim mortality in patients with PAIVS. The purpose of their investigation was to study the risk and cause of interim death in infants undergoing a Blalock-Taussig shunt procedure for palliation of PAIVS. They studied patients with RV hypoplasia that was "significant enough" to require placement of a systemic-to-pulmonary artery shunt in the neonatal period. The definition of significant RV hypoplasia is difficult. The question of RV growth and its contribution to the pulmonary flow, and the prediction of these growths is particularly challenging when a surgical strategy is planned. The tripartite classification of the RV and the size of the tricuspid valve have been proposed as determinants of RV growth.
The 35 infants in the group underwent placement of a systemic-to-pulmonary artery shunt. The authors chose to exclude patients who underwent RV decompression with or without pulmonary valvotomy. Four of the 35 patients did not undergo neonatal cardiac catheterization, and of the remaining 31 infants, only 1 was found to have right ventricular-dependent coronary circulation. As the authors had alluded to, this is significantly less than all the other reported series.
The authors have examined the presence or absence of coronary sinusoids and fistula as independent variables to assess outcome. This is based on the small number of patients with a preoperative diagnosis of right ventricular-dependent coronary circulation. Autopsy examination revealed that the most common cause of death at all stages in this patient population was related to myocardial perfusion. This may reflect a preoperative underestimation of the presence and significance of right ventricular-dependent coronary circulation.
In view of the most common cause of death being related to myocardial perfusion, this important study further emphasizes the need for defining myocardial perfusion and the presence or absence of right ventricular-dependent coronary circulation.
Related Article
Ann. Thorac. Surg. 2004 78: 1994-1998.
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