Impact of successful treatment of acromegaly on overnight heart rate variability and sleep apnea

Abstract

Background: Successful treatment of acromegaly improves disease-related cardiovascular mortality and morbidity, but its effects on autonomic modulation of the heart rate are unknown. Objectives: We documented treatment-induced changes in time-domain heart rate variability, taking into account the confounding effects of obstructive sleep apnea. Patients and Methods: Sixteen consecutive patients (12 males, aged 43 ± 12 y) with newly diagnosed acromegaly underwent overnight (12:00-7:00 AM) cardiac Holter recordings coupled with polysomnography. Data were obtained before and 10 ± 6 months after successful treatment of acromegaly. Results: IGF-1 levels fell from 807 ± 333 to 207 ± 69 μg/L and normalized in all patients. Seven patients (44%) had obstructive sleep apnea (apnea-hypopnea index 33 ± 21/h) at baseline. Treatment had no significant effect on polysomnographic indices. After treatment, increases were noted in the normal-to-normal heart period (NN), SD-NN, the percentage of NN differing from the previous NN by greater than 50 msec, and the root mean square of successive differences in NN (each P