4th practice
Medical Informatics
Biomedical Signal Processing
TAMUS, Zoltán Ádám
zoltanadam_tamus@yahoo.com
 The
most traditional biomedical signal
(stethoscope)
 The PCG is generated by the contractile
activity of the cardiohemic system (the
heart and blood together)
 Recording: microphones, pressure
transducers or accelerometers placed on
the chest surface
 Auscultation
areas for heart sound
 The
heart sound are NOT caused by
valve leaflets movements
 Vibrations of the whole cardiovascular
system
 As the fluid filled balloon when
stimulated any location
 Normal
cardiac cycle contains two major
sounds
• the first heart sound (S1) and the second heart
sound (S2)
 S1
occurs at the onset of the ventricular
contraction (systole)
 S2
occurs at the closure of the semilunar
valves (diastole)
 The
first vibration:
• contractions in the
ventricles
• blood move toward
the atria
• sealing the atrioventricular (AVmitral and tricuspid)
valves
 The
second
component:
• abrupt tension of the
closed AV valves
• decelerating the
blood
 The
third
component:
• the semilunar valves
(aortic and
pulmonary) open
• the blood is ejected
out of the ventricles
• oscillation of blood
between the root of
the aorta and the
ventricular walls
 The
forth
component:
• Turbulence in the
ejected blood
flowing rapidly
through the
ascending aorta and
the pulmonary artery
 The
S2 is caused by
the closure of the
semilunar valves
• Vibrations in the
arteries due to the
deceleration of blood
• Ventricles and atria
also vibrate due to the
transmission of
vibrations through
blood, valves and the
valve rings
 S2
has two components
• First: closure of the aortic valve (A2)
• Second: closure of the pulmonary valve (P2)
 A2
precedes P2 by few miliseconds
 Phatologic conditions could cause this
gap widen or may also reverse the order
of A2 and P2
 In
some cases may
be heard
• sudden termination
of the ventricular
rapid filling phase
• Low frequency:
ventricles filled
blood and their walls
are relaxed
 The
intervals between S1 and S2, and S2
and S1 are normally silent
 Murmurs are caused by certain
cardiovascular defects and diseases
 Murmurs are high frequency, noise-like
sounds
 Turbulence in blood flow
 Rangaraj
M. Rangayyan: Biomedical
Signal Analysis, IEEE Press/Wiley, New
York, NY, 2002.
 1. Analysis of the heart sound
• Observation of the parts of heart sound
 Parts of S1 and S2
• Determination of the heart rate (pulse)
 2. Examination of heart sound in frequency
domain
 3. Examination of murmurs in time and
frequency domain
sample files: http://zoltanadam.fw.hu
software: Audacity http://audacity.sourceforge.net/