Heart rate recovery is impaired after maximal exercise testing in children with sickle cell anemia

Objective To examine heart rate recovery (HRR) as an indicator of autonomic nervous system dysfunction after maximal exercise testing in children and young adults with sickle cell anemia (SCA). Study design Recovery phase heart rate (HR) in the first 5 minutes after maximal exercise testing in 60 subjects with SCA and 30 matched controls without SCA was assessed. The difference between peak HR and HR at both 1-minute (ΔHR_1min) and 2-minutes recovery was our primary outcome. Results Compared with controls, subjects with SCA demonstrated significantly smaller mean ΔHR_1min (23 beats per minute [bpm], 95% CI 20-26 vs 32 bpm, 95% CI 26-37, P =.006) and the difference between maximal HR and HR at 2 minutes (39 bpm, 95% CI 36-43 vs 48 bpm, 95% CI 42-53, P =.011). Subjects with SCA also showed smaller mean changes in HR from peak HR to 1 minute, from 1 minute to 2 minutes, and from 2 through 5 minutes of recovery by repeated-measures testing. In a multivariable regression model, older age was independently associated with smaller ΔHR_1min in subjects with SCA. Cardiopulmonary fitness and hydroxyurea use, however, were not independent predictors of ΔHR_1min. Conclusions Children with SCA demonstrate impaired HRR after maximal exercise. Reduced postexercise HRR in SCA suggests impaired parasympathetic function, which may become progressively worse with age, in this population.