Six Minute Walk Test and Clinical Outcomes in Pediatric Heart Transplant Candidates

Heart transplantation is the main therapeutic option for children and adolescents with cardiomyopathies (CM) and congenital heart disease (CHD) who progress to advanced heart failure. However, longitudinal data on functional capacity in pediatric transplant candidates remain limited. This study aimed to assess exercise tolerance using the six-minute walk test (6MWT) according to diagnosis and clinical outcomes. This prospective longitudinal single-center study included 40 patients aged 8-17 years awaiting heart transplantation. Exercise capacity was assessed using the 6MWT. Longitudinal analyses were performed in 28 patients who completed both initial and final assessments. Clinical outcomes included transplantation, death, or remaining on the transplant waiting list. Overall, 6MWT distance decreased over follow-up (p = 0.031). When stratified by diagnosis, a decline was found only in the CHD group (p = 0.034), whereas values remained stable in CM. Patients with CHD demonstrated lower 6MWT distance compared with CM (p = 0.005), in addition to exercise-induced desaturation, higher Borg scores, higher resting heart rate (HR), and lower heart rate variation (ΔHR) from rest to peak exercise. Patients who died while on the transplant waiting list showed marked reductions in 6MWT performance. Increases in Brain Natriuretic Peptide (BNP) values were observed before clinical outcomes. Functional capacity declined during follow-up in pediatric patients awaiting heart transplantation, particularly among those with CHD. Reduced oxygen saturation, greater perceived exertion, and impaired HR responses during the 6MWT may contribute to lower functional performance. Longitudinal reductions in 6MWT performance may reflect clinical deterioration in pediatric transplant candidates.