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Figure 1 Representative example of the dramatic effect that a single isolated ectopic beat and its correction might have in the measurement of baroreflex sensitivity by the transfer function method (TF-BRS). Tracings (A) show systolic arterial pressure (SAP) and RR interval time series with a ventricular premature complex at the beginning of the recording. Measurement of TF-BRS on these signals gives 1.2 ms/mm Hg, whereas excluding the ectopic beat from the computation (i.e., starting the analysis window from the dashed bar) gives 6.2 ms/mm Hg. Tracings (B) show the same signals after correction of the ectopic beat by linear interpolation. Despite the apparent negligible effect on the fluctuation pattern of the two signals, TF-BRS becomes 4.7 ms/mm Hg, that is, –24% compared with the measurement obtained without the ectopic beat. Although the effect of the correction is not always so dramatic, this example highlights the need to perform a careful check every time a correction is made.
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