Low frequency power of heart rate variability reflects baroreflex function, not cardiac sympathetic innervation

• Published in: Clinical autonomic research Vol. 21; no. 3; pp. 133 - 141
• Main Authors: Rahman, Faisal, Pechnik, Sandra, Gross, Daniel, Sewell, LaToya, Goldstein, David S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2011; Springer Nature B.V
• Subjects: Baroreflex - physiology; Cardiology; Case-Control Studies; Diabetes; Electrophysiologic Techniques, Cardiac - methods; Endocrinology; Gastroenterology; Heart - innervation; Heart - physiology; Heart Rate - drug effects; Heart Rate - physiology; Humans; Hypotension, Orthostatic - physiopathology; Medicine; Medicine & Public Health; Multiple System Atrophy - physiopathology; Neurology; Nitroglycerin - pharmacology; Ophthalmology; Parkinson Disease - physiopathology; Pure Autonomic Failure - physiopathology; Research Article; Sympathetic Nervous System - physiology; Tomography, Emission-Computed; Valsalva Maneuver - physiology; Vasodilator Agents - pharmacology; Power spectral analysis; Parasympathetic; Heart rate variability; Sympathetic; Autonomic
• DOI: 10.1007/s10286-010-0098-y
• ISSN: 0959-9851

Background Power spectral analysis of heart rate variability is used to assess cardiac autonomic function. The relationship of low frequency (LF) power to cardiac sympathetic tone has been unclear. We reported previously that LF power may reflect baroreflex modulation. In this study we attempted to replicate our findings in additional subject cohorts, taking into account possible influences of respiration and using different methods to measure baroreflex-cardiovagal gain (BCG). Objective We assessed relationships of LF power, including respiration-adjusted LF power (LFa), with cardiac sympathetic innervation and baroreflex function in subjects with or without neuroimaging evidence of cardiac sympathetic denervation. Methods Values for LF power at baseline supine, seated, and during the Valsalva maneuver were compared between subject groups with low or normal myocardial concentrations of 6-[ 18 F]fluorodopamine-derived radioactivity. BCG was calculated from the slope of cardiac interbeat interval vs. systolic pressure during Phase II of the Valsalva maneuver or after i.v. nitroglycerine injection (the Oxford technique). Results LF and LFa were unrelated to myocardial 6-[ 18 F]fluorodopamine-derived radioactivity. During sitting rest and the Valsalva maneuver logs of LF and LFa correlated positively with the log of Phase II BCG ( r  = 0.61, p  = 0.0005; r  = 0.47, p  = 0.009; r  = 0.69, p  < 0.0001; r  = 0.60, p  = 0.0006). Groups with Low BCG (≤3 ms/mmHg) had low LF and LFa regardless of cardiac innervation. The log of LF power during supine rest correlated with the log of Oxford BCG ( r  = 0.74, p  < 0.0001). Conclusion LF power, with or without respiratory adjustment, reflects baroreflex modulation and not cardiac sympathetic tone.