In the analysis of HRV the Nerve-Express system uses a very effective and easy to interpret visual representation of Heart Rhythm, called Method of Rhythmography (developed 1967 by Dr. Zhemaitite, Lithuania). Rhythmography draws the time interval between each consecutive heartbeat as a straight, vertical line. The longer the interval between each heartbeat (R - R), the longer the vertical lines (Fig. 1).
Fig. 2 a) Wave "portrait" of Heart Rate Variability
When these lines are graphed sequentially they present a curve-specific, wave portrait of R-R intervals Variability (Fig. 2a).
Rhythmographic representation allows a great deal of information to be compressed in a simple picture. The wave portrait in Fig. 2a is composed of 448 R-R intervals of the ECG. A spectral analysis of this curve allows Nerve-Express to identify two main spectral components (Fig. 2b):
High frequency - 0.5 - 0.15Hz
Low frequency - 0. 15 - 0.04 Hz.
It has been found that there is a high correlation between the power of High-frequency band of the spectrum function and the tone of the Parasympathetic Nervous System (PSNS), and also between the power of Low-frequency band and the tone of the Sympathetic Nervous System (SNS). This finding has been well documented in a number of medical and scientific publications and in conference reports from the American College of Cardiology, The American Heart Association, and others.
Fig. 2 b) Spectral Function of Heart Rate Variability
Nerve Express uses an algorithm, which analyzes not only the Power of High frequency and Low Frequency but also the peaks of amplitudes and its shifting pre-and-post an autonomic intervention, and can graph the relationship between the activity of SNS and PSNS. Nerve-Express uses a principally new classification of ANS, arranged into nine categories.
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