Exercise Capacity Following Pulmonary Embolism in Children and Adolescents

Background: Self-reported physical activity after pediatric pulmonary embolism (PE) is reduced after diagnosis. However, objectively measured exercise capacity and mechanisms of exercise pathophysiology after PE are unknown. Research Question: Does exercise capacity 1 year after acute PE in children differ from control patients? Study Design and Methods: This case-control study compared exercise capacity and responses to maximal exercise in PE survivors with control patients. We also investigated the association of low exercise capacity after PE with prespecified clinical/radiologic features at PE diagnosis and elucidated the cause of functional limitations. The primary study outcome was exercise capacity defined by peak oxygen consumption (V˙O₂peak) as a percent predicted on cardiopulmonary exercise testing (CPET), with < 80% predicted V˙O₂peak considered abnormal/low. Ventilatory inefficiency was defined as ratio of ventilation to CO₂ production on CPET slope > 30 and abnormal stroke volume augmentation as oxygen pulse < 10 mL/beat at peak exercise. Logistic regression was performed to assess the association of prespecified variables with low V˙O₂peak. Results: We compared 25 consecutive pediatric PE survivors who completed CPET 1 year after diagnosis with 25 control patients who underwent CPET within the same period and were otherwise healthy. Exercise capacity was reduced in eight of the 25 PE survivors (32%) at 1 year after diagnosis vs two of the 25 control participants (8%) (P = .034). PE survivors with low exercise capacity demonstrated elevated ratio of ventilation to CO₂ production on CPET slope (P = .01) and a decreased oxygen pulse at peak exercise (P = .001), consistent with cardiovascular limitation. In univariable analysis, PE category, pulmonary vascular obstruction by the Qanadli index, or right ventricular dysfunction at diagnosis was not associated with low exercise capacity. Interpretation: In this study, abnormal exercise capacity of cardiopulmonary origin occurred in one of three pediatric PE survivors despite anticoagulation and irrespective of PE severity, degree of pulmonary vascular obstruction, or right ventricular dysfunction at diagnosis. Cardiorespiratory fitness should be formally considered to develop rehabilitation interventions after pediatric PE.