Estimating Exercise Intensity Using Heart Rate Methods in Children and Young Adults with Pulmonary Hypertension

Standard methods for prescribing exercise intensity in exercise therapy define moderate and vigorous exercise using a percentage of peak heart rate (HR). However, these approaches may be inappropriate for pediatric patients with pulmonary hypertension (PH) due to impaired vasodilatory function, chronotropic incompetence, and because the methods were developed based on adult data. This study aimed to evaluate the accuracy of recommended exercise prescription methods in children and young adults with PH. This retrospective study included patients aged 6-25 years with PH. Accuracy was assessed by comparing HR values for moderate and vigorous exercise zones, defined by traditional methods against a gold standard (GS) derived from cardiac or pulmonary exercise testing using the ventilatory threshold and respiratory compensation threshold. Independent t-tests were used to assess differences between methods, and Bland-Altman plots were used to determine limits of agreement relative to the GS. Data from 134 patients (mean age 17 ± 4 years) were analyzed. For moderate intensity, HR values generated by all three traditional techniques differed significantly from the GS (all p < 0.001). For vigorous intensity, zones based on percentage of peak VO₂ and percentage of peak HR were significantly different from the GS (p < 0.001), whereas zones based on percentage of HR reserve were not (p = 0.558). Bland-Altman analysis showed poor agreement overall, with most cases falling outside acceptable limits of difference (approximately 50-80% of cases). Recommended exercise prescription methods did not accurately define exercise intensity zones in pediatric and young adult patients with PH. Population-specific approaches may improve exercise prescription accuracy in this group.