Prognostic implications of autonomic nervous system analysis in chronic heart failure: Role of heart rate variability and baroreflex sensitivity

Increased sympathetic activity and plasma levels of norepinephrine (NE), parasympathetic withdrawal and impaired baroreflex gain have been reported in chronic heart failure (CHF). It is still debated whether, and if so, to what extent, the marked sympathetic activity influences the survival. Very little data is available on the prognostic implications of baroreflex sensitivity (BRS) and heart rate variability (HRV). Both BRS and HRV have been shown to be markedly reduced in CHF and significantly associated with the degree of ventricular dysfunction and with a further progression of the severity of the disease. Only small studies involving a limited number of patients have correlated these indices to an increased risk of death in CHF. We studied 119 consecutive sinus rhythm patients with mild to severe CHF. It was found that time and frequency parameters of HRV were not different between deceased and surviving patients, while BRS at univariate analysis was significantly associated with mortality; however, this prognostic information was not confirmed in a multivariate model. Although further analyses are necessary, our data and those of the literature do not confirm in CHF the important role which has been attributed to HRV and BRS in post-myocardial infarction risk stratification. In this paper some methodological limitations concerning the measure of these indices in CHF and possible different interpretative keys of the results are discussed to explain the discrepancies.