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The aim of the study was to evaluate cardiorespiratory exercise tolerance in asymptomatic children with Ebstein's anomaly. Eleven children with a mean age of 9.6 years were prospectively studied by spirometry, cardiopulmonary exercise testing (bicycle ergometer n = 8, treadmill test n = 3), and contrast echocardiography. A right-to-left atrial shunt was detected by contrast echocardiography in 7 children (group 1), whereas no shunt was found in 4 (group 2). VO2 max was decreased [84.5 (SD = 16.8)] and was strongly correlated to oxygen saturation in group 1 (p< 0.0001). Oxygen saturation at peak uptake was significantly decreased compared to baseline [97.4 (SD = 2.0) vs 90% (SD = 9.5%), p = 0.02] and was significantly lower in group 1 than in group 2 [85.7 (2.2) vs 98.2% (SD = 1.2%), p = 0. 03]. Oxygen desaturation was related to a right-to-left atrial shunt (p = 0.01). Decreased VO2 max was also correlated to the small size of the left ventricle (p = 0.05). We concluded that decreased exercise tolerance in children with asymptomatic Ebstein's anomaly is related to a right-to-left atrial shunt and to a small left ventricle. In case of poor exercise tolerance, a contrast echocardiography should be performed to detect an atrial septal defect.

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