Can be used as a
prognastic marker of
cardiovascular
diseases and its
application in
estimation of cardiac
autonomic nervous
system activity
(Stauss, 2003)
ANS imbalance associating with increased
SNS and decreased PNS has been strongly
correlated with arhythmogensis and sudden
cardiac death (Sztajzel, 2004).
in a normal heart with an integer
ANS, there will be a continuous
physiological variation of the sinus
cycle reflecting a good
symptho-vagal balance (Sztajzel,
2004)
In healthy individuals the SAN inititiates each heart beat due to an
unstable membrane potential of myocites located within that region,
causing action potentials to be generated at a fairly constant frequency
(Stauss, 2003)
This contstant frequency is generated by the autorhythmicity of the SAN and is modulated
my many factors causing variability in the HR signal at differing frequencies (Stauss, 2003)
According to the task force of european society of cardiology etc classifed these frequencies to be divided in to the following
bands:
ULF (>5hour cycle length);
Associated with circadian rhythm
LF (>6s cycle length)
Sensititive to sympathetic
nervous system (and perhaps
parasympathetic activity)
HF (2.5-6s cycle length)
syncronised with the respiratory
system, and primarily inervated by
parasympathetic innervation
VLF (> 25s cylcle length)
asociated with temp regulation
LF power
Used to help depict SNS which is responsible for speading up the HR,
interestingly can only be depicted by LF due to PNS being much faster than
sympathetic mediated effects of the HR (Straus, (2003), 27, 30 47a
Sympathetic activity
a negative pressure on lower extremity has been
known to increase sympathetic activity (Stauss, 2003)
HF Power
Parasympathic
NS is the only
thing that factors
HF power, but is
also known to
effect LF power (Stauss, 2003)
Most researched componant within HRV due to its
high correlation with vagal modulation (Stauss, 2003)
non-invasive way to detect the sympatetic
and vagal componants of the ANS on
SAN level (Szatjzel, 2004)
Autonomic Nervous
system
Sympathetic nervous activity enhanceds
automoaticacy, wheras Parasympathetic inhibits it
Parasympathic NS is responsible for the hyperpolarisation and
reduce the rate of depolarisation, whereas the sympathetic NS
causes chronotrophic effects by increasing the rate fo SAN
depolarisation (Szatjzel, 2004)
Measurement
HRV analysis consists of a series od
measurements of successive R-R interval
variations of sinus origin, providing information
about autonomic tone (Szatjzel, 2004) 18
Different factors may influence HRV
Age
Gender
Respiration
circardian rhythm
Body position
usually used in 24 hour holter recordings
but can also be used in shorter recordings
between 0.5-5 minutes
Short term
recordings are
caracterised by the
VLF, LF anf HF
componants
The LF/HF ratio reflects
the global
sympatho-vagal balance
and can be used within
this balance.
In a normal adult resting values tend to be around 1-2
Normalisation
LF or HF (nu)= LF or HF/ (total power[ms2]- VLF [ms2])
Effect of Exercise
It is well known that endurance athletes have profound Brachycardia
When comparing HRV indices trained vs general population they have found that trained athletes
have a significantly longer R-R interval
When using absolute values data
has shown mixed results on if
trained atheltes have a higher HF
dominance (Achten & Jeukendrup,
2004) [15, 48, 53] [49, 50, 54]
When using normalised
data 4/6 studies found a
greater vagal dominance, in
trained athletes (Achten &
Jeukend, r, up, 2004)
[28,53,56,58]
Predictor of overtraining?
Could be used to predict overtraining or overreaching
(Achten & Jeukendrup, 2004) [13, 99]