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This Article Full Text (PDF) Free All Versions of this Article: 101/3/1003    most recent 00643.2006v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Karemaker, J. M. Search for Related Content PubMed PubMed Citation Articles by Karemaker, J. M.

POINT-COUNTERPOINT COMMENTS

Cardiovascular variability is/is not an index of autonomic control of circulation

Department of Physiology

Academic Medical Center
University of Amsterdam
Amsterdam, The Netherlands

The following letter is in response to the Point:Counterpoint series "Cardiovascular variability is/is not an index of autonomic control of circulation" that appeared in the August issue (vol. 101: 676-682, 2006; http://jap.physiol.org/content/vol101/issue2/2006).

To the Editor: The Point:Counterpoint discussion on CVV (4) caught my attention as it raises a number of questions about which I also have philosophized in the past (1–3). However interesting the arguments that are put forward, the only difference between the two P:CP camps seems to be the conclusion: may we or may we not use CVV-derived parameters in daily clinical practice? Strangely enough, no one ever questions the outcome of classical autonomic function tests, like the phenylephrine test (5) to "measure" baroreflex sensitivity. Anyone who ever did the test knows that a difference of a factor of two in outcome between successive runs is not uncommon. Underpinning the fact that autonomic outflow from the CNS may be highly variable from moment to moment. Only in neuropathy or after brain injury do we find stable (mostly low) outflow. Continuous variability in nervous activity is a fact of life, and quantification by direct (MSNA) or indirect measurement (CVV) may give only rough estimates of a patients' condition. Much less exact than the concentration of ions in the blood, but telltale when longer periods of illness in one and the same patient are to be followed. There lies, in my opinion, the true power of clinical application of CVV, not in the one-point measurement, unless the condition is extremely clear cut.

REFERENCES

1. Karemaker JM. Heart rate variability: why do spectral analysis? Heart 77: 99–101, 1997.[Free Full Text]
2. Karemaker JM. The riddles of heart rate variability. Clin Auton Res 11: 65–66, 2001.[CrossRef][Web of Science][Medline]
3. Karemaker JM. Why do we measure baroreflex sensitivity the way we do? Clin Auton Res 12: 427–428, 2002.[CrossRef][Web of Science][Medline]
4. Parati G, Di Rienzo M, Castiglioni P, and Mancia G; Taylor JA and Studinger P. Point:Counterpoint: Cardiovascular variability is/is not an index of autonomic control of circulation. J Appl Physiol 101: 676–682, 2006.[Abstract/Free Full Text]
5. Smyth HS, Sleight P, and Pickering GW. Reflex regulation of arterial pressure during sleep in man. A quantitative method of assessing baroreflex sensitivity. Circ Res 24: 109–121, 1969.[Abstract/Free Full Text]

This Article Full Text (PDF) Free All Versions of this Article: 101/3/1003    most recent 00643.2006v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Karemaker, J. M. Search for Related Content PubMed PubMed Citation Articles by Karemaker, J. M.