title: Heart rate variability in heart failure.
abstract: BACKGROUND
  Heart rate variability (HRV) depicts the functional status of the autonomic nervous system and its effects on sinus node. Recently, HRV analysis has been introduced in patients with heart failure (CHF) to identify those who are at risk of cardiac death.
  
  
  OBJECTIVE
  To analyse HRV in patients with CHF with depressed left ventricular ejection fraction (EF) and to relate HRV parameters to EF, NYHA functional class and other clinical parameters.
  
  
  METHODS
  The study group consisted of 105 patients with CHF (88 males, 17 females, mean age 54+/-12 years); 77 patients had ischaemic cardiomyopathy, and 28 - dilated cardiomyopathy. All patients were in NYHA class II-IV and had EF <40%. The mean value of echocardiographically assessed EF was 26.9+/-8.3%. The control group consisted of 30 gender- and age-matched healthy subjects. HRV analysis was performed in the time-domain from 24-hour Holter ECG.
  
  
  RESULTS
  All HRV variables were significantly lower in patients with CHF than in controls. Patients with NYHA class II had higher values of SDNN and SDANN than those in class III or IV. Patients with sustained or non-sustained ventricular tachycardia (VT) detected during Holter monitoring had lower SDNN and SDANN values than those without VT. Patients with diabetes had significantly lower SDNN and rMSSD values than the patients without diabetes. Similar results were found when patients with or without hypertension were compared. HRV parameters were similar in patients either with ischaemic or dilated cardiomyopathy. Also the values of EF were similar (27.4+/-8.4 vs 25.0+/-8.3%, respectively, NS). In the whole group of patients with CHF the values of SDNN and SDANN significantly correlated with EF (SDNN p<0.001, r=0.42; SDANN p<0.001, r=0.51). This correlation was stronger in the subset of patients with ischaemic cardiomyopathy (SDNN p=0.002. r=0.54; SDANN p=0.002; r=0.53) than in those with dilated cardiomyopathy (SDNN p=0.012, r=0.23; SDANN p=0.008, r=0.42). A significant negative correlation was found between all HRV parameters and NYHA class (SDNN p<0.001, r = -0.33; SDANN p<0.001, r = -0.38; rMSSD p<0.001, r = -0.13).
  
  
  CONCLUSIONS
  HRV is depressed in patients with CHF compared with healthy subjects. Among patients with CHF, HRV is further decreased in patients with more advanced NYHA class, lower EF and in those with diabetes, hypertension or VT on Holter monitoring.
mesh_terms: D000328:Adult; D000368:Aged; D002311:Cardiomyopathy, Dilated / Q000150:complications* / Q000503:physiopathology; D016022:Case-Control Studies; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000209:etiology / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications* / Q000503:physiopathology; D011379:Prognosis; D018570:Risk Assessment; D013318:Stroke Volume; D017180:Tachycardia, Ventricular / Q000209:etiology; D013997:Time Factors