Cardiopulmonary exercise testing in children with heart failure secondary to idiopathic dilated cardiomyopathy.

STUDY OBJECTIVE: To determine and compare the cardiopulmonary responses of healthy children and children with heart failure due to idiopathic dilated cardiomyopathy (IC) to progressive treadmill exercise testing. SETTING: University teaching hospital specializing in cardiology. PATIENTS OR PARTICIPANTS: Twenty-six children with stable, chronic heart failure (left ventricular ejection fraction < 45%) caused by IC (IC group) and 12 healthy children (control group). INTERVENTIONS: After 12-lead resting ECG, all children underwent progressive treadmill exercise testing using a modified Naughton protocol. Tests were performed in a controlled-temperature exercise facility, at least 2 h after a light meal. MEASUREMENTS AND RESULTS: Cardiopulmonary parameters were assessed at rest, at anaerobic threshold (AT), and at peak exercise. At rest, the tidal volume (VT) and O(2) consumption (VO(2)) for heart rate (O(2) pulse) were lower, while the heart rate, respiratory rate, and ventilatory equivalent for O(2) (minute ventilation [VE]/VO(2)) were higher in the IC group compared with the control group. At AT, the systolic BP, O(2) pulse, VT, exercise duration, VO(2), CO(2) production (VCO(2)), and VE were lower, while the VE/VO(2) and ventilatory equivalent for CO(2) (E/CO(2)) were higher in the IC group (p < 0.05). At peak exercise, the IC group had a significantly lower systolic BP, O(2) pulse, VE, VT, exercise duration, VO(2), and VCO(2), but higher VE/VO(2) and VE/VCO(2) than the control group (p < 0.05). The VE/VCO(2) slope was significantly higher for the IC group. No correlation existed between variables evaluated at rest vs during exercise. CONCLUSIONS: Gas exchange analysis performed during exercise successfully differentiated children with heart failure from healthy children.