Avaliação do risco de morte através da variabilidade da frequência cardíaca em pacientes com insuficiência cardíaca

Abstract

This study evaluated long-term and short-term heart rate variability (HRV) parameters in patients with suspected heart failure (HF) with at least one hospital admission and who underwent 24 hours ECG monitoring (Holter). After clinical, laboratory and echocardiographic assessment, the patients were divided into subgroups: without heart failure, heart failure with normal, midrange and reduced ejection fraction. The short duration parameters were obtained from the analysis of the lowest SDNN, RMSSD and pNN50 obtained in a period of 10 minutes in each signal. The long duration parameters were obtained after analysis of the 24 hours signal and 6 hours periods during the day and at night to evaluate the circadian behavior of HRV. The main results showed that the lowest 10-min rMSSD was an independent predictor of death especially in older patients with reduced ejection fraction. Thus, short periods of reduced parasympathetic tone increased the risk of death in the studied population. There was a decrease in mean heart rate at night compared to daytime in patients without HF, a fact not observed in patients with HF. The other parameters did not present circadian variations. In the analysis of HRV parameters within the analyzed subgroups, we did not observe significant changes in the long duration parameters, but the lower 10 min SDNN parameter reduced according to the ejection fraction