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Columbia University Validation study report

Research Holtcr Laboratory Columbia University

                   A COMPARISON OF NERVE EXPRESS AND CHRONOS ALGORITHMS

A. Statement of Study Purpose

Heart Rhythm Instruments, Inc. has developed algorithms for power spectral analysis of

RR intervals (the Nerve Express algorithms). Heart Rhythm Instruments, Inc. has packaged

the Nerve Express algorithms in an instrument suitable for stand-alone office use. The

purpose of this evaluation was to compare the Nerve Express algorithms with the "gold

standard" CHRONOS algorithms to test the reliability of the Nerve Express algorithms for

power spectral analysis of RR intervals. The CHRONOS algorithms have been shown to

predict death in coronary heart disease and to quantify physical fitness, but they are

accessed via Holter technology and are not packaged as a stand-alone office instrument.

The Nerve Express algorithms are conveniently packaged for office use. If they are

equivalent to CHRONOS, they would constitute a reliable office system useful for many

purposes: assessment of risk in cardiovascular disorders; assessment of physical

fitness; documentation of benefit for cardiac, chiropractic, or orthopedic

rehabilitation; and quantification of drug effects on the autonomic nervous system.

B. Background and Rationale

Power spectral measures of normal RR intervals recorded for a short (5 minute)

or long (24-hour) period of time predict cardiac death in patients with coronary heart

disease or valvular heart disease and in random samples of middle-aged persons (1-10).

Power spectral measures of normal RR intervals also provide an excellent measure of

physical fitness (11-14). Short-term recordings of the ECG show cyclic fluctuations that

are well characterized by frequency domain methods, either non-parametric fast Fourier

transforms or parametric autoregression (15-17). These methods are capable of

quantifying the energy of cyclic fluctuations in RR intervals. The joint Task Force on

Heart Rate Variability of the European Society of Cardiology and the North American

Society for Electrophysiology and Pacing recommended that, for assessment of autonomic

modulation of RR intervals, frequency domain methods be applied to 5-minute ECG

recordings (17). Frequency domain analysis reveals two peaks of energy (power) in the

power spectra obtained with these methods: a low frequency peak (LF) that represents

modulation of RR intervals by baroreflex activity and a high frequency peak (HF) that

represents modulation of RR intervals by breathing. The vagus nerve carries efferent

impulses in both cases. High values for measures of RR interval variability indicate

greater physical fitness and a prognosis.

The CHRONOS algorithms developed jointly by The Research Holter Laboratory at

Columbia University and Dr. Jeffrey N. Rottman are the best-documented algorithms for

predicting cardiac death in patients with coronary heart disease (18). However, data for

the landmark studies with the CHRONOS algorithms were acquired using Holter recorders, a

cumbersome way to acquire short-term data in the office. Also, highly trained research

technicians have extensively edited ECG recordings before the CHRONOS algorithms are

applied to them.

Nerve Express is a PC-based system for assessing the state of the autonomic nervous

system using proprietary power spectral technology developed over a 15-year period. The

algorithms are packaged for convenient office use, but the ability of the Nerve Express

algorithms to predict cardiac death or physical fitness has not been validated. The

purpose of the current research is to test the reliability of the Nerve Express

algorithms for power spectral analysis of RR intervals by comparing them with the CHRONOS

algorithms.

If the Nerve Express algorithms prove reliable for predicting death and/or predicting

physical fitness, this system will be the first convenient,

inexpensive tool for the office assessment of cardiovascular risk and physical fitness

will finally be available.

2 06/05/98

Research Holler Laboratory Columbia University

The Research Holter Laboratory at Columbia University has conducted many studies to

document the ability of the CHRONOS algorithms to predict cardiac death and/or physical

fitness. Heart Rhythm Instruments, Inc. has developed Nerve Express algorithms to

analysis fluctuations in RR intervals. Among these are routines to process artifact and

ectopic beats in the RR data stream. These routines have the potential to make Nerve

Express more fully automated which will not only broaden the venues in which the

instrument can be used but also decrease the cost of assessing the autonomic nervous

system by reducing expensive technician time.

E. Conclusion

The results of our comparison of the Nerve Express algorithms with the CHRONOS algorithms indicate that the results obtained are similar and suggest that the Nerve Express algorithms should predict death in coronary heart disease and level of physical fitness.

 

P.S. Heart Rhythm Instruments, Inc and trade name "Nerve-Express"  are
     original names of Fitness Score product.
     Copy of full study report available upon request.