High mid-flow to vital capacity ratio and the response to exercise in children with congenital heart disease

BACKGROUND: Pulmonary mechanics may play a role in exercise intolerance in patients with congenital heart disease (CHD). A reduced FVC volume could increase the ratio between mid-flow (FEF_25-75%) and FVC, which is termed high dysanapsis. The relationship between high dysanapsis and the response to maximum-intensity exercise in children with CHD had not yet been studied. The aim of this work was to examine whether high dysanapsis is related to the cardiopulmonary response to maximum-intensity exercise in pediatric subjects with CHD. METHODS: We retrospectively collected data from 42 children and adolescents with CHD who had either high dysanapsis (ratio >1.2; n = 21) or normal dysanapsis (control) (n = 21) as measured by spirometry. Data extracted from cardiopulmonary exercise test reports included peak values of heart rate, work load, V_O2, V_CO2, and ventilation parameters and submaximum values, including ventilatory threshold and ventilatory equivalents. RESULTS: There were no significant differences in demographic and clinical parameters between the groups. Participants with high dysanapsis differed from controls in lower median peak oxygen consumption (65.8% vs 83.0% of predicted, P =.02), peak oxygen pulse (78.6% vs 87.8% of predicted, P =.02), ventilatory threshold (73.8% vs 85.3% of predicted, P =.03), and maximum breathing frequency (106% vs 121% of predicted, P =.035). In the high dysanapsis group only, median peak ventilation and tidal volume were significantly lower than 80% of predicted values. CONCLUSIONS: In children and adolescents with corrected CHD, high dysanapsis was associated with a lower ventilatory capacity and reduced aerobic fitness, which may indicate respiratory muscle impairments.