7th Symposium of IMAB, 24-27 of May, Varna
HEART RATE VARIABILITY IN MEDICAL PRACTICE
National Center of Hygiene
Medical Ecology and Nutrition Sofia, Bulgaria
Heart rate variability (HRV) is the spontaneous oscillation of beat-to-beat
time intervals (expressed in ms) around the mean value (pulse in beats/m).
It is mirroring the sympathetic-parasympathetic (vagal) balance. This makes
it a valuable tool for investigation of the autonomic nervous system in
almost all medical branches. HRV measurements are easy to perform, are
noninvasive and have reliable reproducibility under standardized experimental
Many factors associated with sympathetic prevalence can decrease HRV:
physical or mental stress, thyreotoxicosis, medications (including different
kinds of doping) etc. HRV decrease also with increasing age, in diabetic
patients due to diabetic cardiomiopathy, in hypertensive patients, acute
myocardial infarction, severe brain damage, overtraining etc. So why, any
time the sympathetic tone is find to be increased, it is accepted as an
increase of health risk score.
PHYSIOLOGICAL BASIS OF HRV
The physiological basis of HRV are the fluctuations of the activity
in brain cardiovascular vasoconstrictory and vasodilatatory centers. Normally
these fluctuations are a result of blood pressure oscillation (baroreflex
modulated); respiration (parasympathetically mediated via thoracic stretch
receptors); thermoregulation (sympathetically mediated via thermoregulatory
peripheral blood flow adjustments) and circadian biorhythm. All these factors
can influence the length of beat-to-beat intervals, named cardiointervals
or R-R intervals. Their values are the object of mathematical estimation
yelding the amount of HRV.
As the increase or the decrease of HRV are reflected by both: the difference
of the length of cardiointervals (expressed with a time based measurements
as ms), and the difference of the spectral power (expressed with a frequency
based measurement as Hz), there exists two types of HRV measures:
a) time-domain based HRV measures
The time domain indexes are relatively easy to calculate and can be
devided to two classes: the first is based on the differences between every
cardiointerval and their mean value. This is cardiointervals standard deviation
(SD); the second is based on the differences between every cardiointerval
and the next one ( ) (1). Both are named "short term variability" (STV).
Long term variability (LTV) indexes are the same, but based on the means
of every five successive cardiointervals (from every five, one cardiointervals
is produced). There are many others time-domain based indexes which are
included in the mathematical algorythms for assessment of the medical phenomena
being studied (2, 3). These indexes are highly correlating with STV and
b) frequency-domain based HRV measures
The submission of cardiointervals to frequency-domain based analysis
requires fast Fourier-transform in order to obtain their power density
spectrum. It yelds information about the amount of variance connected with
oscillations of heart rate at various spectral frequencies and is measured
in milliseconds squared (ms2). As the spectral power associated with the
long spectral waves (0.01 - 0.05 Hz, thermoregulation) is namely sympathetically
modulated, and the spectral power associated with the short spectral waves
(0.2 - 0.4 Hz, respiration) is namely parasympathetically modulated, their
ratio is used for description of the autonomic balance. Middle spectral
waves (0.06 - 0.16 Hz, blood pressure are less informative. Frequency-domain
based indexes can be also used for assessment of "mental stress", because
this type of stress is activating the higher levels of the cardiovascular
regulation centers (cortical), producing variability in the area of the
long spectral waves. For this assessment some distinguishing with thermoregulatory,
peripheral vasomotor or renin-angiotensin contribution is provided.
MEASUREMENT OF HRV
Ordinary HRV measures are obtained from a 10 minute sequence of cardiointervals.
Cardiointervals can be elected from: ECG, plethysmogram, phonocardiogram,
but predominantly ECG signal is used.
HRV IN DIFFERENT MEDICAL AREAS
a) Cardiology and cardiovascular diseases
A reduction of vagal tone is found to be associated with acute myocardial
infarction (so HRV can be used as a prognostic tool in postinfarktion period).
HRV has a high association with the risk for sudden cardiac death, and
arrhythmic complications (4). Diminished vagal activity is found in patients
with coronary artery disease and essential hypertension. After heart transplantation
the allograft rejection can be predicted by decreased total spectral power.
HRV reflects autonomic dysfunction of central origin in patients with
parkinsonism, spinocerebellar degeneration, Shy - Drager syndrome, multiple
sclerosis, chronic alcoholism, Guillan - Barre syndrome, quadriplegia etc.
c) Diabetes mellitus
Diabetic cardiomiopathy is marcably decreasing HRV. As this decrease
is ofently preceding clinical symptoms, HRV can be used for early prediction
of the diabetic pathology (5), especially in children.
d) Glomerulonephrites with renal insufficiency
Decrease of vagal tone was found in uremic patients, revealed namely
by the diminution of the short waves-associated spectral power.
e) Pharmacological influence
Calcium channel blockers (as atenolol f.e.), beta-blockers (as diltiazem
f.e.), tranquilisers, relaxants, scopolamine (vagomimetic), etc. are increasing
the time as well as the frequency-domain HRV measures. Contrary, atropine
is decreasing vagal activity (2). It is interesting to note, that nifidipine
(Ca-blocker) has not effect upon HRV.
HRV analysis can reveal the severity of autonomic dysfunction caused
by environmental neurotoxic agents as organic solvents, pesticides, nitrates,
organophosfates, leads etc.
g) Work-lelated stress
Vibratory tool operations, inconvenient regimes of work and rest, dust
of different kinds, ergonomical disadvantages, overload, bad psychological
microclimate etc. can decrease HRV. This is used for their quantitative
assessment and control (3).
h) Medical ecology
Ecological hazard needs to be evaluated not only by measuring of the
level of ecological noxes, but also by the impact they have upon common
functional status of the population living in ecologically contaminated
areas. This can be done, before all, by following up the chronically increased
sympathetical tone by HRV measurements.
The status of overtraining as well as the effect of relaxation procedures
and the use of forbidden medicaments (doping) can be successfully controlled
j) Applied psychology
By multiple step regression analysis is found that phenomena as depression,
burnout, lack of social support, uncontrolled locus of control, bad family
or social relations etc. are increasing the long waves spectral power and
decreasing the total spectral power.
k) Unconventional medical treatments
The effect of manual therapy, traditional chinese therapies, aromatherapy,
massages, sauna, autogene training, yoga, Silva method etc. is difficult
to be assessed without following their impact upon common functional status,
which is reflected by HRV.
l) Transport, army and cosmic medicine
All these professions or activities presuppose a high level of health
reserves and adaptation capacities. It was found, that the physical as
well as the mental effort (6) required in these cases can be reliably evaluated
by HRV measurement.
m) Health (life) insurance
Recently some attempts to use HRV as a predictor of overall health
risk (as a factor influencing insurance conditions) are done in Norway
COMERCIALLY AVAILABLE HRV EQUIPMENT
As the use of HRV analysis increases, the need for commercially available
HRV equipment is also increasing. The conventional Holter monitors are
not convenient for HRV measurements because of variations in tape speed.
Modern ECG apparatuses include STV, LTV and spectral analyses, but they
are expensive and the obtained measures are not sufficient. Some specialized
hard and software HRV equipment�s are also very expensive and posses too
narrow professional destination. From another side all these apparatuses
are not supplied with a reliable correction for artificially short or long
R-R intervals and algorithm for extrasystoles recognition. These disadvantages
are removed by the created in National Center of Hygiene Medical Ecology
and Nutrition "Health Check - Danev tests" (DaTe).
DATE are 3 tests based on HRV analysis: 1. assessment of stress and
pathological changes of heart rhythm; 2. assessment of physical fitness;
3. assessment of health risk (%). The last tests is based on the results
obtained by the first two tests.
DATE are developed in the last 7-8 years on the basis of thousands
investigated by HRV persons.
n) The advantage of DATE
a) DaTe software
- assessment not only of STV, LTV and frequency-based HRV measures,
but also of the physical and mental stress. This is possible due to the
implementation of a new statistical approach named "singular value decomposition"
performed in the space of Karunen-Loew, which yields information about
the main HRV components accompanying these phenomena.
- assessment of the normality of cardiac rhythm (number of ventricular
premature heart beats)
- assessment of physical fitness (training) by a testing procedure
including repeated postural changes form siting to standing up five times
- assessment of functional age and vitality level.
- assessment of HRV based health risk (%). This method proved
to be very reliable (3, 7).
- establishing of age-related bioconstant values for all HRV
- perfect modern realization of both: DOS and Windows DATE versions.
- possibility to be adjusted to the specific demands of the separate
- easy to be learned without special medical or computer education.
b) DaTe hardware
-DATE specialized devices for conversion of ECG signal to cardiointervals
are produced in Denmark or Norway in accordance with EC requirements.
- electronically simple and very reliable construction being
long time in use without serious defects.
- two types of hardware being available: first, working simultaneously
with PC (IBM compatible) and second, working separately with possibility
to transmit accepted data to PC on line or latter.
- electromagnetic and humidity isolation.
- low price and 2 years warranty.
Where Danev tests were used
Danev tests were used successfully in:
- work physiology for assessment of work-related health risk,
overfatigue; shift work load; specific demands posed by different kinds
of industrial production (electrical-power stations; TV retranslating stations;
still, cooper, silver and gold productions; agriculture; cotton production;
chemical plants etc.
- children hygiene for prediction of diabetes and essential hypertension
- sport: heavy lifting, box, athletics alpinismus
- surgery to control the operation stress
- air and sea forces in hypobaric or hyperbaric cameras
- transport medicine in personal of electric trains
- chip building industry (noise and vibration).
- alternative medicine for controlling it's effect.
As Danev tests are used also in Norway, Denmark, Germany, Japan and
USA, their advantages were confirmed by the work in many scientific and
applied medical directions.
Medical or related specialists needs easy and reliably methods for quantitative
evaluation of autonomic tone, because it is the main moderator of health
and illness (7). HRV analysis is providing such a possibility. HRV based
Danev tests proved to be a convenient tool for this purpose, aimed to help
all medical branches where sympathetical-to-parasympathetical balance have
to be controlled.
Fig 1 gives example of time-domain and frequency domain based HRV indexes
obtained by DATE in: A-parasympathetic prevalence and B-sympathetic prevalence.
1. Danev S., G. F. Wartna, B. Bink, J. Radder, L. Lutein. Psychophysiological
assessment of informational load. Nederlands tijdschrift voor de psychologie,
XXVI, 1971, 1, 29-39.
2. Danev S., E. Datzov, S. Svetoslavov. Pharmacologically induced sympathetic
or parasympathetic influence upon heart rate variability in man. Acta medica,
3. Danev S., S. Svetoslavov, E. Datzov. Heart rate variability - an
objective criterion for prediction of health risk in vorkers. Acta medica,
4. Odemuyiwa O. et all. Multifactorial prediction of arrhythmic events
after myocardial infarction. Combinations of heart rate variability and
left ventricular ejection fraction with other variables. Pace. 1991, 14.
5. Pfeifer MA et all. Quantitative evaluation of cardiac parasympathetic
activity in normal and diabetic man. Diabets. 1982, 31.
6. Vicente K. et all. Spectral analysis of sinus arrhythmia: a measure
of mental effort. Human factors, 1987, 29 (2).
7. Danev S., Sv. Svetoslavov, E. Datzov. A chronic decrease of
heart rate variability can precede some cases of cancer. 3rd world congress
on cancer, Darvin Australia, April, 1997.
Key words: HRV
Address: Prof. Dr. Sv. Danev NCHMEN, 15 D. Nesterov bvd., 1431 Sofia,
Fig. 1. Main DaTe measures in: A. Parasympathetic and B. Sympathetic
Physical Stress = 144 Mental Stress = 194
Physical Stress = -233 Mental Stress = -156