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Autonomic compensation to central hypovolemia monitored with heart period variability
Author(s) -
Convertino Victor A.,
Rickards Caroline A.,
Ryan Kathy L.,
Cooke William H.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1229.2
Subject(s) - medicine , heart rate variability , baroreflex , cardiology , presyncope , heart rate , blood pressure , autonomic nervous system
A controversy exists as to whether components of heart rate variability may serve as indices of autonomic control of the circulation (JAP 101:676–682, 2006). We tested the hypothesis that frequency‐domain components of R‐R interval variability track autonomic function during progressive reductions in central blood volume induced by lower body negative pressure (LBNP) in humans. Subjects (n=33; 23 M/10 F) were instrumented to record ECG and muscle sympathetic nerve activity (MSNA; peroneal nerve) during a progressive LBNP protocol to cardiovascular collapse (i.e., presyncope). Although MSNA recordings were lost in many subjects during LBNP, MSNA was maintained through cardiovascular collapse in 12 subjects. Heart period variability was assessed by calculating the power spectral density in the high frequency (RRI HF ; 015–0.4 Hz) and low frequency (RRI LF ; 0.04–0.15 Hz) domains with a fast Fourier transform. RRI LF and RRI HF correlated poorly with MSNA at baseline (R 2 ≤0.01). LBNP caused a progressive reduction in R‐R interval and a progressive increase in MSNA. LBNP produced a progressive reduction (p<0.001) in RRI HF but failed to elicit distinguishable (p=0.15) alterations in RRI LF . As a result, RRI HF demonstrated a high, inverse amalgamated correlation with MSNA (R 2 = 0.98), but a low amalgamated correlation existed between MSNA and RRI LF (R 2 = 0.09). Our data show that RRI LF is not an accurate index of sympathetic compensation to progressive reductions in central blood volume. Conversely, reductions in RRI HF may serve as an accurate, non‐invasive index of elevated sympathetic activity.