Introduction: Ventricular arrhythmias substantially increase the risk of mortality and morbidity in pati-ents with heart failure (HF). Data from the literature show that heart rate variability (HRV) parameters are correlated with arrhythmic risk and mortality in pati-ents with HF with reduced ejection fraction, but there is little information about patients with HF with inter-mediate (HFmEF) or preserved (HFpEF) ejection frac-tion.

Objective: To evaluate the prevalence of ventricular ar-rhythmias in relation to HRV parameters by ECG Hol-ter monitoring in patients (pts) with chronic HF with mEF vs pEF.

Methods: 130 patients with chronic compensated HF, under treatment, mean age 67.6 ± 11.5y, 52.9% men, in sinus rhythm, no active myocardial ischemia or electrolyte disturbances were included: 52 (40%) with HFmEF and 78 (60%) with HFpEF. The parameters for 24 hour ECG Holter monitoring were: heart rate- mini-mum (HRmin), maximum (HRmax), mean (HRmed), ventricular arrhythmias, standard HRV parameters in time domain: SDNN (standard deviation of iNN inter-vals between 2 QRS complexes of the sinus rhythm), RMSSD (square root of the mean square of the succes-sive iNN differences), pNN50 (iNN proportion that differs >50ms) and HRV parameters obtained by spec-tral analysis: LF (low frequency power) and HF (high frequency power).

Results: There were no significant differences between HRmed (67 ± 9.8 vs. 68.6 ± 9.9 vs., pNS), HRmin (44.4 ± 8 vs. 46.8 ± 8, pNS), HRmax (111.1 ± 25.4 vs.113.7 ± 21.9, pNS), SDNN (129.8 ± 46.89 vs. 124.53 ± 44.53, pNS). Patients with HFmEF, with more oft en history  if coronary artery disease (58% vs.44%, p=0.014), had more frequent ventricular arrhythmias: ventricular extrasistoles (VE) (794.2 vs. 760.9, p=0.045), ventricular tachycardia (23.08% vs. 6.41%, p=0.0078) and higher  HRV parameters: RMSSD (55.7 ± 38.1 vs. 40.26 ± 27.6,p=0.009), pNN 50 (14.5 (min 1, max 740) vs.7.5 (min 0, max 72) p=0.004), LF (585.3 (min 82.1, max 4896.7) vs.458.4 (min 58.6, max 4598.1), p=0.034) and HF (309.3 min 42.7, max 1246.6) vs. 166.05 max 1436.7),
p=0.013). Th e VE number correlated signifi cantly with the HRV parameters in the time domain: RMSSD (r=0.23, p=0.04), pNN50 (r=0.22, p=0.011) and in the frequency domain: LF (r=0.34, p=0.009), HF (r=0.26, p=0.03).
Conclusions: Ventricular arrhythmias have a higher incidence in patients with HFmEF than in those with HFpEF, which correlates with elevated HRV parameters. Under pathological conditions, greater variability in heart rate may contribute to increased arrhythmic risk.