Six-minute walking distance and decrease in oxygen saturation during the six-minute walk test in pediatric pulmonary...

Area of Science:

• Pediatric Cardiology
• Pulmonary Hypertension
• Clinical Exercise Physiology

Background:

• Pediatric pulmonary arterial hypertension (PAH) is a severe condition requiring accurate prognostic markers.
• The 6-minute walk test (6-MWT) is commonly used to assess exercise capacity in various conditions, including PAH.
• Understanding the prognostic value of 6-MWT parameters in children with PAH is crucial for guiding treatment and management.

Purpose of the Study:

• To evaluate the prognostic significance of 6-minute walking distance (6-MWD), transcutaneous oxygen saturation (tcSO2), and heart rate (HR) during the 6-minute walk test (6-MWT) in pediatric PAH patients.
• To determine if these parameters can predict transplant-free survival in this population.
• To identify the most effective combination of parameters for prognostic modeling.

Main Methods:

• An observational study involving 47 pediatric PAH patients (age ≥7 years) at a national referral center.
• All patients underwent a comprehensive 6-MWT, measuring 6-MWD, tcSO2, and HR at baseline, during exercise, and during recovery.
• Statistical analysis was performed to assess the association of 6-MWD and tcSO2 changes with transplant-free survival, adjusting for relevant clinical factors.

Main Results:

• The 6-MWD, in meters or z-scores, was independently associated with transplant-free survival, irrespective of sex, age, or shunt presence.
• Shorter 6-MWD correlated with higher WHO functional class and elevated NT-pro-BNP levels.
• Absolute exercise tcSO2 and the decrease in tcSO2 during the 6-MWT also predicted transplant-free survival independently of 6-MWD. A combination of 6-MWD and tcSO2 decrease yielded the strongest prognostic model. Significant tcSO2 decrease identified patients with worse outcomes, regardless of 6-MWD or shunt status.

Conclusions:

• The 6-MWD is a validated, independent predictor of prognosis in pediatric PAH, reflecting disease severity and exercise tolerance, and can serve as a treatment target.
• The magnitude of tcSO2 decrease during the 6-MWT, adjusted for shunt presence, provides additional prognostic information in children with PAH.
• Combining 6-MWD and tcSO2 decrease offers a robust model for predicting outcomes in pediatric PAH.