title: The effect of the year angiotensin-converting enzyme inhibitors (ACE I) intake on circadian heart rate variability in patients with primary hypertension.
abstract: BACKGROUND
  The autonomic nervous system (ANS) disturbances have been considered as one of the important factors in development of essential hypertension. However information about the effect of antyhypertensive treatment (angiotensin-converting enzyme inhibitors--ACEI) on cardiac ANS activity is ccscarce.
  
  
  OBJECTIVE
  The purpose of the study was to evaluate the HRV circadian changes in patients with essential hypertension, treated with ACEI throughout the period of one year.
  
  
  METHODS
  Ten patients with essential hypertension, aged 26 to 64 years (mean 54.3 +/- 12.3) and 10 healthy volunteers, matched for age and gender were qualified for the investigation. Twenty four-hour arterial blood pressure measurements with simultaneous ECG monitoring were conducted in both mentioned groups. The hypertensive patients were examined before and after 1 year of ACE inhibitor (enalapril) intake. HRV analysis was carried out by the fast Fourier transformation (FFT). The time and spectral parameters were compared in 8 examined subjects characteristic for dippers, in time periods of day (6 a.m.-10 p.m.) and night (10 p.m.-6 a.m.).
  
  
  RESULTS
  The results obtained before the treatment, likewise in control group, presented night's increases of RMSSD (p < 0.05), pNN50 (NS, p > 0.05), VLF, LF (p < 0.05) and HF (NS) mean values with a decrease of LF/HF ratio (p < 0.05). Similar tendencies in the cardiac ANS activity were observed after 1 year of the enalapril intake. A comparison of day's HRV before and after one year of the ACE inhibition presented the increase in values of the parasympathetic system reflecting parameters: RMSSD, pNN50 (p = 0.01) and HF (NS) with a decrease of LF/HF ratio (p < 0.01). The evaluation of the night's HRV parameters presented the increase of HF mean value (p < 0.05), without any other significant changes between the trials.
  
  
  CONCLUSIONS
  After 1-year of ACE inhibitor administration the only improvement of the day's parasympathetic activity was observed. The night's vagal activity suggested as one of the essential factor in development of hypertension remained unchanged in patients qualified into "dippers" hypertension group.
mesh_terms: D000328:Adult; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors