Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Heart rate variability
Standards of measurement, physiological
interpretation, and clinical use
Based on a Review article by Task Force of The European Society of
Cardiology

E
...

• It is a measurement of central autonomic drive to the

myocardium
...

• In contrast to many conventional tests to evaluate autonomic
nervous system, HRV analysis stands as a non invasive method
of detecting an early autonomic impairment of heart
...


• However in healthy individual resting HR would never be that high
...

– This represents the net effect of the parasympathetic (vagus)

nerves, which slow HR, and the sympathetic nerves, which
accelerate it
...


Sources of Heart Rate Variability
• Extrinsic
– Activity
– Mental Stress
– Physical Stress

- Sleep Apnea
- Smoking

• Intrinsic Periodic Rhythms
–
–
–
–
–
–

Respiratory sinus arrhythmia
Baroreceptor reflex regulation
Thermoregulation
Neuroendocrine secretion
Circadian rhythms
Other, unknown rhythms

Basis of HRV

History of HRV
• 18th Century Albrecht von Haller noticed heart beat is not

regular
• The clinical relevance of heart rate variability was first
appreciated in 1965 - Hon & Lee noticed that the beat to beat
interval changes are the first alteration before fetal distress
occurs
...


• 1971 Sayers and others focused on rhythm imbedded in beatto-beat HR
• 1972 Ewing et al devised a number of simple bedside tests of
short-term RR differences to detect autonomic neuropathy in
diabetic patients

History of HRV
• 1977 Wolf et al showed association of HR to sudden death post

MI
• 1981 Akselrod introduced Power Spectral Analysis (PSD)
• Late 1980’s HRV confirmed strong predictor of mortality after an
acute MI
• 1996 Task Force published Standards of Measurement for HRV
...


About The Task Force
• The task force was established by the Board of the European

Society of Cardiology and co-sponsored by the North American
Society of Pacing and Electrophysiology
...
To standardize nomenclature and develop definitions of
terms

2
...
To describe currently appropriate clinical applications
4
...


Stress And Autonomic Nervous System

Stress And Autonomic Nervous System
• Allostasis which means "maintaining stability, or homeostasis,

through change
...

– Most of the time it succeeds but the real problems arise when…
...

(2) The balance between SNS and PNS can be disturbed and either SNS
or PNS can predominate over the other leading to stress related health

problems
...

• These methods are further divided into statistical and

geometrical methods
...


• The current geometric methods are inappropriate to
evaluate short term recordings
...
g
...
g
...
g
...
g
...


Statistical methods
• Complex Time Domain Measures
• SDNN
• SDANN

• SDNNindex
• SDSD

• RMSSD
• NN50

• PNN50%

24 hour HRV Recording

Statistical methods
• SDNN (ms) - Standard deviation of the RR intervals, which
reflects all the cyclic components responsible for variability in
the period of the recording
...


Statistical methods
• SDANN (ms) - Standard deviation of the averages of NN intervals in

all 5 min segments of the entire recording
...


• where N is total number of 5 minute sections RR intervals in selected
segment,
• RR5 is mean of RR intervals in 5 minute section,
• RR is mean of all means of RR intervals in all 5 minute sections
...

• it measures the variability due to cycles shorter than 5 min
...


Statistical methods
• RMSSD (ms) - Root mean square of successive differences in RR
intervals
• This measure estimate high-frequency variations in heart rate in
short term RR recordings

• NN50 - number of successive differences between R-R intervals
greater than 50 ms
• It’s used for classification of the segment longer or at least 5 minutes
...

• TINN - Triangular interpolation of NN interval

– Baseline width of the minimum square difference
triangular interpolation of the highest peak of the

histogram of all NN intervals
– T INN = M − N

Frequency Domain Methods
• Frequency domain method of analysis is one of the key factors
of HRV analysis
• Various spectral methods for the analysis of the tachogram have
been applied since the late 1960s
...

• PSD estimation provides the basic information of how the
power of the signal (i
...
, its variance) distributes as a function of
frequency
...


Frequency Domain Methods
• Absolute Measures
–
–
–
–
–

TP – Total power 0 to 0
...
003 Hz
VLF – very low frequency band 0
...
04 Hz
LF – low frequency band 0
...
15 Hz
HF – high frequency band 0
...
4 Hz

• Relative Measures
• The normalization minimizes the effect of changes of Total Power (TP)
on LF and HF
– Lfnorm = LF / (TP-VLF), unit n
...

– Hfnorm = HF/(TP-VLF), unit n
...

– LF/HF - Ratio of low to high frequency power

Nonlinear methods for HRV analysis
• In this context, nonlinear methods, based on chaos theory and

fractal analysis, have been applied in order to better understand
the nonlinear phenomena underlying HRV
• These methods includes
– Poincar´e plot
– Detrended Fluctuation Analysis (DFA)
– Shannon entropy
– Approximate entropy (ApEn)
– Sample entropy (SampEn)
– Fractal dimension

INTERPRETATION
• TIME DOMAIN ANALYSIS (5 minutes)
• MEAN HRT (BPM)
• Mean HRT is the average heart rate during 5 minutes
...

• Bradycardia: If the HRT is slower than 50 beats per minute
...
Thus, it provides long-term information
...


• SDNNindex (ms) - The Index is believed to be a measure
primarily of autonomic influence on heart rate variability
...

• It reflects an estimate of parasympathetic regulation of the
heart
...

• Decrease in RMSSD (RMSSD: below 10) accompanying

lowered SDNN (below 20) is related to high risk of cardiac
disease development
...


• These measurements correspond to short-term HRV
changes and are not dependent on day/night variations
...

• Compared to pNN50, RMSSD seems to be more stable
and should be preferred for clinical use
...
In practice,
recordings of at least 20 min (but preferably 24 h) should be
used to ensure the correct performance of the geometric
methods
...
4 Hz
...


INTERPRETATION
• Frequency Domain Parameters
• Very Low Frequency (VLF) (ms2) – Very Low Frequency is a
band of power spectrum range between 0
...
04 Hz
...

• In short term analysis, VLF doesn’t provide much meaning since

this band often reflect meaningless noise signals
...

• Role in obstructive sleep apnea syndrome

INTERPRETATION
• Frequency Domain Parameters
• Low Frequency (LF) (ms2) - Low Frequency is a band of power
spectrum range between 0
...
15 Hz
...

• Generally it is a strong indicator of sympathetic activity
...

• Thus, when subject is in the state of relaxation with a slow and
even breathing, the LF values can be very high indicating
increased parasympathetic activity rather than increase of
sympathetic regulation
...
15 and 0
...

• This measure reflects parasympathetic (vagal) activity
...

• Heart rate is increased during inhalation and dropped during
exhalation
...


HF and RSA

INTERPRETATION
• Frequency Domain Parameters
• LF/HF Ratio - This is the ratio between the power of Low
Frequency and High Frequency bands
...

• Higher values reflect domination of the sympathetic system,
while lower ones reflects domination of the parasympathetic
system
...


Importance of LF – HF ratio

INTERPRETATION
• Frequency Domain Parameters
• Normalized Low Frequency (LF Norm) (%) - is the ratio
between absolute value of the Low Frequency and difference

between Total Power and Very Low Frequency
...


• LF norm= LF/(TP-VLF)*100= LF/(LF+HF)*100

• Frequency Domain Parameters
• Normalized High Frequency (HF Norm) (%) - is the ratio
between absolute value of the High Frequency and difference

between Total Power
and Very Low Frequency
...

• HF norm= HF/(TP-VLF)*100= HF/(LF+HF)*100

Summary of Frequency domain methods

Short term and Long term HRV Time and
Frequency Domain Measures

Short term and Long term HRV Time and
Frequency Domain Measures
• Shows balanced behavior of the 2 branches of the autonomic
nervous system
• Normalized units should be quoted with absolute values to
describe the distribution of spectral components
• Short term recording (5 minutes)
– VLF is not reliable
• Long term recording (24 hours)
– Results include ULF also

– Problem is the heart period modulation responsible for LF
and HF is not stationary during 24 h

Correlation between time and frequency domain measures

Interpretation
• Non linear Methods
• Point care plot analysis

Normal values of standard measures of HRV
• Even though that there are no widely accepted standard values
for HRV that can be used for clinical purposes, The Task Force of
the European Society of Cardiology and North American Society
of Pacing Electrophysiology provided initial normative values of
standard measures of HRV

Reference values

USAGE OF HRV IN DAILY CLINICAL PRACTICE

HRV AND DISEASES

Clinical and physiological importance of HRV
analysis

Nenad Lakusic et al
...

• Although the Task Force recommends rMSSD better than
pNN50 because its higher mathemathical robustness
...
, 2012

Shemaila Saleem et al
...
,2006

R Virtanen et al,
...
, 2013

Raj Kumar Yadav et al
...
Singer et al,
...

• The connection between health and the amount of variation in

the heart rate was noted as early as the third Century AD
...

• Lowered HRV is associated with aging, decreased autonomic

activity, hormonal tonus and specific types of autonomic
neuropathies
...


• The contemporary non-parametric and parametric spectral
methods are probably sufficient to analyse short-term ECGs
without transient changes of heart period modulations
...

• The geometrical methods are only one possibility
in this direction

Summary

Summary

“According to Darwin’s Origin of Species, it is not the
most intellectual of the species that survives; it is not
the strongest that survives; but the species that
survives is the one that is best able to adapt and
adjust to the changing environment in which
it finds itself

---