| Sumario: | Purpose The evaluation of baroreflex sensitivity (BRS) is an assessment tool of autonomic control of the cardiovascular system. BRS might be a risk factor for several cardiovascular diseases1. The assessment of BRS was computed as the square root of the ratio between electrocardiographic (ECG) RR interval and systolic pressure (SBP) spectral components. However, it is not convenient to measure the dynamical SBP. In this study, we use Pulse Transit Time (PTT) as a surrogate signal of SBP to measure BRS2. Method The Physionet Fantasia Database is an archive of bio-signals for use by the research community3. We downloaded ten young (21-34) and ten elderly (68-85) healthy subjects' bio-signals . All participants had 120 minutes ECG and provided an uncalibrated continuous non-invasive blood pressure signal. Each heartbeat was annotated and the RR interval was then computed. PTT was definite from the intervals between ECG R peak and SBP waveforms peak (Figure 1). Traditionally, BRS and Coherence were computed in the 0.07--0.14Hz frequency range with following equation, where POWRRI_SBP is the cross power spectrum and POWRRI_SBP(f), POWRRI_SBP(f) mean the power spectrum of RRI and SBP. ... Because the Fantasia database has only uncalibrated SBP signals, we used POWPTT(f) as a surrogate of POWSBP(f). Results & Discussion Figure 2 is a scatter plot showing the distribution of individual BRS and Coherence values among the 20 subjects. Both BRS and Coherence were significantly lower in the elder group compared with young (BRS=6.36±4.19 vs. 13.48±5.14, respectively, P=0.0032; Coherence=0.2±0.06 vs. 0.4±0.08, respectively, p=0.0001). The agerelated loss of BRS may reflect the degradation of integrated cardiovascular regulatory systems. This novel method not only reduces the difficult in measuring dynamical systolic pressure, but also has the potential application of evaluating the aging effect.
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