HEMODYNAMIC EVALUATION BEFORE AND AFTER CLOSURE OF FENESTRATED FONTAN - AN ACUTE STUDY OF CHANGES IN OXYGEN DELIVERY

Background. Acute changes in hemodynamics and oxygen delivery accompanying temporary occlusion of atrial defects in 14 patients after a fenestrated Fontan procedure were evaluated at a median interval of 32 days after surgery to identify candidates for permanent transcatheter closure of their defects. Methods and Results. Patients ranged in age from 9 months to 33 years and in weight from 7.9 to 69 kg. Right atrial (RA), left atrial (LA), and aortic pressures, mixed venous (SmvO2) and aortic (SaO2) oxygen saturation, and whole-body oxygen consumption (VO2) were measured, and systemic blood flow (Qs), systemic oxygen transport (SOT), and oxygen extraction were calculated before and after occlusion. SmvO2, VO2, and RA pressures did not change, but SaO2 increased from 84+/-6% to 95+/-3% (p<0.05), and LA pressures fell from 5.1+/-3.6 to 3.7+/-2.2 mm Hg (p<0.05). Qs fell from 2.4+/-0.7 to 1.8+/-0.4 l . min-1 . m-2 (p<0.05), SOT fell from 425+/-154 to 366+/-112 ml . O2 . min-1 . m-2 (p<0.05), and oxygen extraction increased from 0.40+/-0.12 to 0.46+/-0.13 (p<0.05). Only one patient did not undergo definitive closure of his defect because of a marked decrease in Qs and SOT with a significant rise in RA pressure. Conclusions. Although delayed closure of an atrial defect in these patients improved morbidity and mortality, the complete separation of the venous and systemic circulations was accomplished at the expense of decreased Qs and oxygen delivery despite the improved level of arterial oxygenation. The resting levels of oxygen extraction are elevated and will be associated with decreased exercise capability. The long-term benefits of closure of these fenestrations are yet to be shown.