Fontan Fenestration Closure Has No Acute Effect on Exercise Capacity but Improves Ventilatory Response to Exercise

ObjectivesThe aim of this study was to prospectively examine the effects of elective Fontan fenestration closure upon exercise capacity and ventilatory abnormalities.BackgroundFor patients undergoing Fontan procedures as palliation of single ventricle physiology, the addition of a fenestration to the procedure mitigates perioperative morbidity. Although some fenestrations may close spontaneously, many remain patent and subject patients to arterial hypoxemia and risk for paradoxical emboli. For these reasons fenestration closure is routinely performed post-operatively in the cardiac catheterization laboratory. Although closure of Fontan fenestrations typically results in an immediate improvement in systemic arterial oxygen saturation, it is also associated with an acute decrease in cardiac index and systemic O2 delivery. The sum result of these physiologic changes upon exercise capacity has not been examined.MethodsTwenty consecutive patients, age 5 to 46 (median 10) years, underwent pre- and post-fenestration closure exercise testing with expiratory gas analysis.ResultsBefore fenestration closure, peak oxygen consumption (VO2) was depressed and there was systemic desaturation at rest that worsened with exercise. The ventilatory response to exercise was also abnormal, characterized by elevation of the minute ventilation (VE)/CO2 elimination slope (VE/VCO2), a low end-tidal CO2, and high end-tidal O2 at the ventilatory anaerobic threshold. Although arterial saturation improved significantly after fenestration closure, there was no change in peak VO2 (70.9 ± 18.6% to 74.0 ± 18.6%, p = NS), heart rate, or O2 pulse at peak exercise. In contrast, ventilatory abnormalities (VE/VCO2) improved considerably (44.4 ± 10.9 to 33.3 ± 5.5, p ≤ 0.001).ConclusionsFontan fenestration closure does not significantly improve peak VO2. However, ventilatory abnormalities improve considerably.