Abstract 2138: Fontan Fenestration Closure Has No Effect On Exercise Capacity But Improves The Ventilatory Response To Exercise
Introduction: For patients undergoing Fontan procedures for palliation of single ventricle physiology the addition of a fenestration to the procedure, which permits intracardiac right-to-left shunting, mitigates perioperative morbidity. While some fenestrations may close spontaneously, many remain patent and subject patients to arterial hypoxemia and risk for paradoxical emboli. For this reason fenestration closure is routinely performed post-operatively in the cardiac catheterization laboratory. Fenestration closure typically results in improved arterial oxygenation, but decreased cardiac index. We assessed the hypothesis that sum effect of these physiologic changes would have not improve exercise capacity.
Methods: Nineteen consecutive patients, age 4.8–46 (median 10) years underwent pre and post-fenestration closure exercise testing with expiratory gas analysis.
Results: Prior to fenestration closure, peak oxygen consumption (VO2) was low. Arterial desaturation was present at rest and worsened with exercise. The ventilatory response to exercise was excessive, characterized by elevation of the minute ventilation vs. CO2 production slope (VE/VCO2 slope) and a low end tidal pCO2 at the ventilatory anaerobic threshold (pETCO2). Following fenestration closure, arterial saturation (at rest and at peak exercise) improved significantly. However, there was no change in VO2, heart rate, or oxygen pulse at peak exercise. In contrast, ventilatory abnormalities improved considerably. The VE/VCO2 slope fell 25% and pETCO2 rose from 27.9+/−4.2 to 34.1+/−3.2 mmHg.
Conclusion: Elective Fontan fenestration closure does not improve peak VO2. However, the reduction in right-to-left intracardiac shunting improves arterial oxygen saturation during exercise and reduces the patient’s need to ventilate during exercise. These changes may reduce the Fontan patient’s perception of dyspnea during exercise.