The reproducibility of cardiac baroreceptor activity assessed non-invasively by spectral and sequence techniques

Abstract

Baroreceptor sensitivity (BRS) is increasingly used as a prognostic indicator in cardiovascular disease. Traditionally it has been measured using invasive techniques with pharmacological manipulation of blood pressure (BP). With the advent of newer methods to measure pulse interval and beat-to-beat changes in BP it is now possible, using sophisticated mathematical modelling techniques, to calculate cardiac BRS non-invasively. However, there are virtually no data on the reproducibility of these newer techniques and what factors may affect the repeatability of these measurements. We studied 39 subjects, aged 22-82 years, with a supine systolic BP range 97-160 mmHg and a diastolic BP range 57-94 mmHg on two occasions between 1 week and 6 months apart. Cardiac BRS was measured by power spectral analysis using Fast Fourier Transformation (FFT), sequence analysis (using up, down and combined sequences) and from phase IV of the Valsalva manoeuvre. There was no significant difference between visits for any of the methods for measuring cardiac BRS. Mean BRS values were similar for FFT (16.7 +/- 11.2 ms/mmHg) and sequence analysis (15.8 +/- 11.4 ms/mmHg); however, results using phase IV of the Valsalva manoeuvre were significantly lower (8.1 +/- 2.9 ms/mmHg, p < 0.0001). The coefficient of variation for the five measures of cardiac BRS varied from 16.8% for Valsalva-derived values to 26.1% for 'down' sequence analysis. However, in ten subjects BRS could not be calculated from the Valsalva manoeuvre. None of the independent variables tested (including age, BP levels and time between testing) significantly influenced the degree of repeatability. In summary, there appears to be little difference between these non-invasive methods in their degree of reproducibility. These techniques would seem suitable for longitudinal studies of changes in cardiac BRS and overcome many of the problems associated with the invasive pharmacological methods.

Oxidative stress and baroreflex sensitivity in healthy subjects and patients with mild-to-moderate hypertension

“…This method was used widely in many studies to assess the BRS. [32][33][34] Both sequence methods and CSP further showed that BRS was decreased in patients with mild-tomoderate hypertension. 35 In our study, BRS in sequential analysis was found, as in the literature, 36,37 to depend on age, gender, DBP, SBP and HR.…”

Continuous cardiac baroreceptor measurement during tilt in healthy elderly subjects

“…The more frequently used method to obtain non-invasive estimates of cardiac BRS, frequency-domain analysis with the FFT algorithm, has intrinsic limitations regarding the temporal resolution that is required for continuous monitoring of BRS [12-14, 17, 19-22]. As an alternative, we explored a time-domain approach, derived from sequence analysis, a technique that is closer to the classical evaluation of BRS function based on drug-induced changes in BP [6,14,19]. In a previous investigation we studied the influence of the number of beats and the time lag of a moving window on the correlation (or the so-called cross-correlation) between Values are given as mean ± SD Table 2 Systolic blood pressure (SBP) and pulse interval (PI) values after tilt SBP and PI [16].We concluded that the ideal approach to improve the temporal resolution of sequence analysis is to use a moving window with only 3-beats and a time lag of 0 beats between the ABP and PI sequences [16].…”

“…Previous work has shown that supine BRS measurements are reproducible in healthy elderly and hypertensive subjects using spectral and sequence analyses [14,15]. We wished to assess the changes in BRS before, during and after tilt and the changes that may recur to these measurements over a period of time using a novel mathematical model.…”

Older subjects show no age-related decrease in cardiac baroreceptor sensitivity

“…All subjects were examined using a standardized protocol [15]. They were asked to attend in the morning after abstinence from caffeine, nicotine or alcohol-containing products for at least 12 h and at least 2 h after breakfast.…”