The modified Fontan operation for complex cardiac anomalies associated with subaortic obstruction entails a high surgical risk. It is likely that ventricular hypertrophy secondary to chronic pressure overload plays a significant role. This problem was approached with a new type of palliative operation comprising both a proximal pulmonary artery to ascending aorta anastomosis and a bidirectional cavopulmonary anastomosis. This operation was performed in six children ranging in age from 26 to 63 months. There was one intraoperative death due to hemorrhage. In one patient, a pulmonary to aorta conduit caused compression of the right coronary artery; the problem was solved by lengthening the conduit with a second period of cardiopulmonary bypass. The five survivors experienced an uneventful postoperative course. Repeat cardiac catheterization in these five patients showed low pressure in the cavopulmonary system (mean 10 mm Hg), absence of a gradient at rest between the systemic ventricle and aorta and fair arterial oxygenation (mean 82%). A technetium-99m perfusion lung scan visualized a slight prevalence of pulmonary blood flow ipsilateral to the shunt in three cases, whereas in one case preferential flow to the right lung was associated with a narrowing at the site of the cavopulmonary anastomosis. Mild hypoperfusion of the anterior pulmonary segments was observed in two cases. Both pressure and volume overload are abolished with this procedure and a satisfactory oxygenation is provided. Low venous pressure in the coronary, hepatic and renal areas as well as the short bypass time may explain the smoothness of the postoperative course in our patients. It is conceivable that oxygenation can be improved by a modified Fontan operation at a lower operative risk than is obtained with a single stage procedure because of regression of ventricular hypertrophy. Long-term follow-up indicates the value of this operation as a form of definitive palliation.
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