Baroreceptor-heart rate reflex sensitivity does not simply mirror the pathophysiological substrate of HF. A depressed BRS conveys independent prognostic information that is not affected by the modification of autonomic dysfunction brought about by beta-blockade.

In CHF patients in sinus rhythm, TF-BRS conveys relevant clinical and prognostic information, but its measurability is markedly affected by ectopic activity. Nevertheless, a TF-BRS-based risk index carrying significant and independent prognostic information can be computed in almost all patients.

Background: Periodic Breathing (PB, waxing and waning of tidal volume in which hyperventilation alternates with periods of apnoea or hypopnoea), is common during sleep and wakefulness in patients with Heart Failure (HF) and may increase mortality. Aim: To assess the effect of short-term, day-time PB on prognosis, in HF patients. Methods: We prospectively studied 380 consecutive HF referrals who had a 10 min, supine day-time respiratory recording. We related PB (adjusted for known predictors) to total cardiac mortality, during a median follow-up of 41 months. Results: Day-time PB occurred in 145/380 patients who had more severe HF and more compromised left ventricular function (p b 0.005). Survival curves began to separate after 10 months and diverged steadily over the next 4 years with a cumulative risk of 41% (PB) vs 26% (No-PB), p = 0.002. PB was independently predictive of increased cardiac mortality when entered into a clinical prognostic model (including NYHA Class, LVEF, LVEDD, Systolic Arterial Pressure, beta-blocker treatment, peak VO2 and blood urea) with a RR: 1.8, 95% CI 1.20-2.81. Conclusion: In advanced HF the presence of PB during a short day-time recording adds to known predictors of cardiac mortality. This may have practical implications for trials of HF therapy.

To assess the accuracy of spectral indices of arterial pressure variability and baroreflex sensitivity obtained from beat-by-beat noninvasive blood pressure recordings by the Finometer device, we compared these measures with those obtained from intra-arterial recordings. The performance of the Finometer was also compared to the traditional Finapres device. In 19 cardiac disease patients, including myocardial infarction, heart failure and cardiac transplant, we estimated the power of systolic and diastolic pressures in the VLF (0.01-0.04 Hz), LF (0.04-0.15 Hz) and HF (0.15-0.45 Hz) bands and computed absolute and percentage errors relative to intra-arterial brachial pressure. We also computed the characteristic frequency of each band (i.e. the barycentric frequency of spectral components identified in the band). The variability of systolic pressure in the VLF and LF bands was markedly overestimated by both the Finometer and Finapres (p < 0.01), with percentage median errors of respectively 130% and 103% (Finometer), and 134% and 78% (Finapres). The HF power was substantially unchanged using the Finometer and reduced using the Finapres (-28%, p < 0.05). The limits of agreement between noninvasive and invasive spectral measurements were wide. Linear system analysis showed that most (>80%) of the power of noninvasive signals was linearly related to the power of the invasive signal. The characteristic frequency of each band was substantially preserved in both noninvasive signals. The results for diastolic pressure were similar, but the Finapres errors in the VLF and LF bands were lower. Baroreflex sensitivity was significantly underestimated by both devices (Finometer: -31%, Finapres: -24%). Despite previous studies having shown that brachial artery waveform reconstruction performed by the Finometer has improved the accuracy of blood pressure measurement compared to the Finapres device, measurement of blood pressure variability in cardiac disease patients provides worse results in most spectral parameters and a better accuracy only in the HF band of systolic pressure.

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