Heart rate variability is reduced in acromegaly patients and improved by treatment with somatostatin analogues.

BACKGROUND: Cardiovascular complications, including arrhythmias and cardiac sudden death, are the most common causes of enhanced mortality in acromegaly. However, few data are available on cardiac autonomic functions and sympathovagal balance in acromegalic patients.
OBJECTIVE: The aim of this study was to investigate both the time and frequency domain parameters of Heart Rate Variability (HRV), in order to characterize the cardiac autonomic functions in patients affected by acromegaly. This study correlated anthropometric, metabolic, echocardiographic parameters and blood pressure with those relating to HRV, to identify the main factors responsible for the HRV related alterations possibly present. We also aimed to analyze the effects of the treatment with somatostatin analogues (SSAs) on HRV.
MATERIALS AND METHODS: This study enrolled 47 acromegalic patients (23 males, age 49.1 ± 13.5 years) and 37 (13 males) age matched (52.3 ± 13.3 years) healthy subjects. All participants underwent 12-lead 24 h ECG Holter recordings and a HRV analysis of the ECG tracings was performed. The parameters obtained from the time domain analysis of HRV included pNN50, SDNN, SDNN index, SDANN and RMSSD. The power spectral analysis of HRV was obtained by summing powers of the LF (low frequency) and the HF (high frequency) band. Sympathovagal balance was estimated by calculating the LF/HF ratio during 24 h and 15 min of clinostatism. The HRV of 28 acromegalic patients was studied before and after SSAs treatment.
RESULTS: Acromegalic patients showed significantly lower SDNN and SDANN compared to controls. Diabetic and non-diabetic acromegalic patients showed decreased SDNN and SDANN, when compared to healthy subjects. Diabetic acromegalic patients had a lower LF/HF ratio during 24 h when compared to non-diabetic acromegalic patients. Similar results were obtained analyzing patients affected by acromegaly and impaired glucose tolerance. SDNN and SDANN were lowered by hypertension in the acromegalic population, when compared to controls, and hypertensive acromegalic patients also displayed a decreased LF/HF ratio during 24 h when compared to normotensive acromegalic subjects. Patients with ventricular arrhythmias in Lown classes 3-5 showed a decreased SDANN compared to patients in Lown class 0-2. The treatment with SSAs was able to ameliorate all the time domain parameters of HRV, without altering the 24 h LF/HF ratio.
CONCLUSION: Cardiac autonomic functions and sympathovagal balance are altered in patients affected by acromegaly and could be ameliorated by SSAs therapy. HRV analysis allows an estimation of the autonomic sympathovagal balance and may be a useful clinical tool for the cardiac risk stratification in acromegalic patients.