Comments: Twenty-three percent of patients born with tricuspid atresia will have D-transposition of the great vessels. While the majority of patients with tricuspid atresia and normally related great vessels will require surgical intervention in the first few months of life for augmentation of pulmonary blood flow, those with transposition commonly have a clinical course marked by heart failure. Heart failure in this latter situation may occur secondary to unrestricted pulmonary arterial blood flow with or without inadequate systemic blood flow, as the aorta may arise from a diminutive outflow chamber with a potentially restrictive VSD. Any restriction at the site of the bulboventricular foramen (subaortic VSD) will further increase pulmonary blood flow at the expense of systemic blood flow (see Fig. 67-5 ). Surgical options include pulmonary artery banding to restrict pulmonary blood flow, a Damus-Kaye-Stansel procedure plus Blalock-Taussig shunt to bypass aortic outflow tract obstruction and control pulmonary blood flow, or a palliative arterial switch procedure wherein ventriculoarterial continuity is restored by connecting the aorta to the larger LV and connecting the pulmonary artery to the smaller RV. Such a procedure entails coronary artery translocation to the neoaorta. The latter option not only ensures unobstructed aortic blood flow but also restores the morphologic LV to its position as the systemic ventricle. Pulmonary artery banding has been associated with restriction of the bulboventricular foramen, or VSD, and late adverse outcome following the Fontan procedure.

PLE is a serious late complication occurring in 4% to 13% of Fontan patients. Clinical features include hypoalbuminemia, ascites, pleural effusions, diarrhea, malaise, and lymphocytopenia. Fecal alpha-1-antitrypsin levels increase prior to the development of hypoalbuminemia and clinical symptoms. The mortality rate is 40% to 56% within 5 years. Medical therapies effective in some, but not all, include high-dose spironolactone, heparin, and corticosteroids. The mechanism of PLE remains poorly understood and does not necessarily relate to poor Fontan hemodynamics. Fontan revision and orthotopic heart transplantation have sometimes been successful in refractory cases.

Other long-term complications following the atriopulmonary Fontan include thromboembolism in 10% to 25%, sinus node dysfunction and atrial arrhythmias in 20% to 56%, Fontan pathway obstruction, coronary sinus hypertension, decreased ventricular function, and increasing cyanosis secondary to collateral circulation and right-to-left shunting of various types.

The natural history of the VSD in tricuspid atresia is a relative decrease in size with an associated increase in LV-to-RV obstruction (with a form of subaortic stenosis in patients with transposed great arteries). This is often precipitated by volume unloading, as occurs with the Fontan or Glenn procedure.

Comments: The exercise test employed an incremental ramp protocol with increments of ¼ Watt per kg of body weight per minute. The protocol is designed to achieve an exercise duration of between 8 and 12 minutes. This duration is designed to achieve a maximal cardiac and pulmonary effort.

Oxygen saturation at rest was 96% and at peak exercise was 92%, which was within normal limits for the test altitude (5200 feet).

There has been a significant reduction in her exercise capacity from a study 2 years previously. A reduction in ventilatory efficiency is common in patients following a Fontan procedure. This may be secondary to elevated pulmonary artery pressures, elevated left heart filling pressures, chest wall deformities secondary to previous thoracotomy or VQ mismatch. Chronotropic incompetence is also common following Fontan palliation and will adversely affect exercise capacity.

Exercise testing with collection of metabolic data is a useful diagnostic tool for determining the timing of listing for heart transplantation. Such testing has been documented to be safe with a low risk of adverse events in outpatients with congestive heart failure in the setting of palliated congenital heart defects. A peak oxygen consumption of less than 14 mL/kg/min is used as a criterion for listing in an adult population without congenital heart disease. This value is not applicable to the child or young adult with congenital heart disease who will often have a higher peak V o ₂ at the time of heart transplantation. A more applicable cutoff value may be a peak oxygen consumption less than 50% predicted. Similarly, a peak oxygen pulse of less than 10 mL/beat, which has been used as an indication for heart transplantation in the adult without congenital heart disease, may not be applicable in this instance.