Point-Counterpoint Comments

Abstract

The following letter is in response to the Point:Counterpoint series "Cardiovascular variability is/is not an index of autonomic control of circulation" (vol. 101: 676 -682, 2006). To the Editor:The heart rate variability (HRV) Point:Counterpoint discussion raises a whole range of questions, and our attention has also been attracted by the topic.The differentiation of vegetative, sympathetic, and parasympathetic contours is an anatomical (or physiological) approach only. Per se, all the contours form a well-organized orchestra and any influence on one contour alters the others, so that they respond like a single whole.Although it has been shown that HF reflects parasympathetic influence and LF reflects sympathetic and parasympathetic influences, different regulation contours exist in all domains. Thus we suppose that it is more correct to use the terms fast/mean/slow regulation contours instead of vegetative/sympathetic/parasympathetic. The advantage of such an approach is that it provides a better representation of the actual interrelationships.We developed a new method, Spectral Independent Component Analysis (SICA; Ref. 1), which demonstrates the competence of such an approach. The use of SICA for HRV analysis allows for the obtainment of no more than three rhythmogramforming components. These components are spectrally presented in all frequency domains, and their focal points correlate precisely with fast/mean/slow regulation contours.In addition, HRV registration should take place in quasistationary conditions, but standard analysis methods are useless in transition processes investigation. In our book (2), we proposed a mathematical apparatus for estimation of transition indexes, which describes transition processes and answers the question: "Is present HRV registration stationary?" If not, the spectral analysis results cannot be regarded as correct, and ,in this case, transition indexes will help to find the parts of rhythmogram where it is possible to apply spectral analysis.HRV is similar to all other methods in modern clinical practice with their strong and weak sides. Successful HRV application fulfills all requirements for measurements and proper results interpretation. REFERENCES