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Heart rate variability (HRV) is mainly determined by the influence of both branches of the Autonomic Nervous System over the sinus node. Low HRV has been associated with a worse prognosis in patients with sepsis. The objective of this study was to explain the reduction in HRV during experimental sepsis in adult rats. We recorded the heart's electrical activity by telemetry in conscious unrestrained male rats before and 1day after the induction of peritonitis (N =39) or sham peritonitis (N =15). Then, we analyzed the chronotropic responsiveness of the isolated heart to the autonomic neurotransmitters and determined catecholamine concentrations in blood plasma and acetylcholine and choline concentrations in the right atrium. The surviving septic rats (N =33) had increased heart rate (HR) and diminished HRV. Despite the higher HR in situ, the spontaneous basal HR in septic and sham isolated hearts was the same. The isolated septic hearts showed acetylcholine hypersensitivity (log (IC50,M)=−7.2±0.2 vs. −6.0±0.4, P =0.025) and lower concentrations of choline in their right atriums (in nMol/mg protein: 0.6±0.1 vs. 1.6±0.6, P =0.013). Norepinephrine concentration in blood plasma from septic rats was higher (in ng/ml: 29.2±8.4 vs. 5.8±4.1, P =0.019). In conclusion, septic rats present a deregulation of the autonomic nervous system, not only sympathetic overexcitation but also parasympathetic dysfunction. [ABSTRACT FROM AUTHOR]

Heart rate variability related to heart rate decelerations and accelerations is reduced in patients with type 1 diabetes compared to healthy individuals both in resting 10-min and ambulatory 24-h ECGs. [ABSTRACT FROM AUTHOR]

Abstract: We have analyzed simultaneous recordings of respiration and heartbeat intervals in diabetic patients and control subjects. Our main findings are that in diabetic patients the heart beat-to-beat interval variability and cardiorespiratory crosscorrelation are decreased, the autocorrelation time of the interval series is increased, and the phase relation of the respiration with the heartbeat interval oscillations is often reversed in comparison with the control subjects. We have been able to reproduce the data using a biophysical model in which the time dependent input signal to the sinoatrial node was constituted of quasiperiodic and aperiodic components. The quasiperiodic input was obtained from the recording of the respiratory signal and the aperiodic input was obtained from selected realizations of correlated noise. Our study indicates that both input components to the sinoatrial node are modified in diabetic patients. [Copyright &y& Elsevier]