title: Determination of baroreceptor-stroke volume reflex sensitivity by power spectral analysis: a quantitative probe of baroreceptor-cardiac reflex.
abstract: Baroreceptor-cardiac reflex, which consists of baroreceptor-induced chronotropic and inotropic actions, is a very useful index of cardiac sympathovagal balance. Baroreceptor-heart rate reflex sensitivity, which reflects baroreceptor-induced chronotropic action, has been used as a marker of baroreceptor-cardiac reflex. However, it cannot be used in patients with chronotropic incompetence and/or implanted cardiac pacemaker. We hypothesized that baroreceptor-stroke volume (SV) reflex sensitivity, which reflects baroreceptor-induced inotropic action, may also be a useful method for measurement of baroreceptor-cardiac reflex, similar to the baroreceptor-heart rate reflex sensitivity. To test this hypothesis, we measured baroreceptor-SV reflex sensitivity expressed as ratio of low frequency (LF) power to total power of SV fluctuation (LF/TP(SV): %/mmHg) by spectral analysis of mean blood pressure and SV fluctuations, the gain in low-frequency band between two signals in supine and 60 degrees upright positions, and compared these values to baroreceptor-heart rate reflex sensitivity in 14 healthy subjects. Baroreceptor-SV reflex sensitivity correlated significantly with baroreceptor-heart rate reflex sensitivity (r = 0.73, p < 0.0001). In addition, baroreceptor-SV reflex sensitivity correlated significantly and positively with high frequency (HF) power (r = 0.57, p < 0.005) and negatively with LF/HF ratio (r = -0.57, p < 0.005) in power spectral analysis of R-R interval variability. Moreover, baroreceptor-SV reflex sensitivity in LF/TP(SV) correlated positively with the R-R interval (r = 0.70, p < 0.0001) and negatively with diastolic blood pressure (r = -0.50, p < 0.01). We conclude that baroreceptor-SV reflex sensitivity in LF/TP(SV) can be used as a quantitative probe of baroreceptor-cardiac reflex, similar to the baroreceptor-heart rate reflex sensitivity in healthy subjects, and it may enable us to estimate inotropic aspect in baroreceptor-cardiac reflex in patients with chronotropic incompetence and/or implanted pacemaker.
authors.affiliation: First Department of Medical Technology, School of Health Sciences, University of Occupational and Environmental Health, Yahatanishi, Kitakyushu, Japan. t_yasu@health.uoeh-u.ac.jp
authors.forename: Tomiya
authors.initials: T
authors.lastname: Yasumasu
authors.forename: Kazuo
authors.initials: K
authors.lastname: Takahara
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Abe
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Nakashima
mesh_terms: D000328:Adult; D017704:Baroreflex; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012016:Reference Values; D012018:Reflex / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013318:Stroke Volume / Q000502:physiology*; D016683:Supine Position