B105-15 Exercise Capacity and Dyspnea on Exertion in Children From 3- to 12-months Post Pulmonary Embolism

Rationale The incidence of pulmonary embolism (PE) is increasing in children. A subset of pediatric patients develops post-PE syndrome, potentially characterized by reduced exercise tolerance and dyspnea on exertion (DOE). However, the trajectory of functional recovery remains poorly understood, particularly within the first year. Furthermore, this course may depend upon which symptom is of primary focus and how recovery is defined (i.e., exercise intolerance or DOE). This study evaluates exercise capacity and DOE in patients from 3- to 12-months post-PE and controls, focusing on differences between participants based on (1) initial exercise capacity and (2) perceived breathlessness (RPB) during submaximal exercise. Methods Exercise capacity (peakV˙O2) was determined 3- and 12-months after first-episode acute PE, in children 13-21 years old without comorbidities and age matched controls. RPB (Borg scale 0-10) was determined during constant-load cycling at 40% of predicted maximum work rate. Pulmonary functional tests (PFTs) were performed at both time points. At 3-months, post-PE participants were categorized into two groups by peakV˙O2: normal (≥80%predicted) and low-capacity (<80%predicted). A separate analysis categorized participants by RPB during constant-load exercise: -DOE (RPB<3) and +DOE (RPB≥3). Results The low-capacity group (n = 11) had persistently lower peakV˙O2 at 12 months compared to the normal capacity group (n = 27) (group P=.0001) (Figure 1). No significant group or temporal differences were observed for peak exercise cardiac output-to-work rate slope (Qc slope), minute ventilation (V˙E), respiratory exchange ratio (RER), or end-tidal CO2 (PETCO2). At steady state, the low-capacity group demonstrated higher RPB, V˙O2 (% predicted), heart rate, RER, and V˙E at 3 months. By 12 months, RPB declined in the low-capacity group compared with the normal capacity group (interaction P=0.05), while other parameters remained unchanged (Figure 1). Ventilatory equivalent (V˙E/V˙CO2 ratio/slope) and DLCO showed no group or time differences. In the dyspnea-based analysis, the +DOE group (n = 13) had lower peakV˙O2 at both time points than the -DOE group (n = 25) (group P = 0.013) (Figure 1). RPB decreased from 3 to 12 months in +DOE participants, but no differences emerged between groups in V˙E, RER, stroke volume, Qc slope, or PETCO2 during peak exercise. Steady-state V˙O2, V˙E, heart rate, RER, V˙E/V˙CO2, and DLCO remained comparable between groups and across time. Conclusion Dividing groups by either RPB or peakV˙O2 did not elucidate different relationships among data. Interestingly, exercise capacity showed no improvement over 9 months but despite this, DOE did improve. These data suggest a perceptual or psychophysiologic contribution to genuine symptom burden.