iTONE Trial (exercIse Training in pulmONary hypertEnsion) Exercise Program for Pediatric PH

Inclusion Criteria: * Age 8-18 years * PH World Health Organization (WHO) diagnostic groups 1, 2, 3, or 4 (pulmonary arterial hypertension, PH due to left heart disease, PH due to lung disease, chronic thromboembolic PH) * WHO functional class I or II * Ambulatory status * Mean pulmonary to systemic arterial pressure ratio \<0.75 if the patient has not undergone a pulmonary to systemic artery shunt ("Potts" shunt) OR the placement of a Potts shunt ≥ 6 months prior to study enrollment * Stable PH medication regimen for 3 months prior to the intervention * Home Wifi connection * Mobile device in family capable of receiving text messages Exclusion Criteria: * WHO functional class III or IV * Single ventricle physiology * Moderate to severe renal disease (\>stage 3) * Severe hepatic impairment \[aspartate aminotransferase (AST)/alanine transaminase (ALT) \> 2x upper limit of normal\] * Current pregnancy * Significant developmental delay/inability to comply with verbal instructions to complete the study procedures