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Heart Activity Measurements Edit Varga Heart Activity Measurements Pulse rate ECG/EKG – electrocardiogram Impedance cardiogram, IKG -- impedance cardiography EchoKG – echocardiogram Magnetocardiography (MCG) Artery’s pulsation Heart Activity Measurements Pulse rate

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heart activity measurements2
Heart Activity Measurements
  • Pulse rate
  • ECG/EKG – electrocardiogram
  • Impedance cardiogram, IKG -- impedance cardiography
  • EchoKG – echocardiogram
  • Magnetocardiography (MCG)

Heart Activity Measurements

heart activity measurements4
Heart Activity Measurements
  • Pulse rate
  • ECG/EKG – electrocardiogram
  • Impedance cardiogram, IKG -- impedance cardiography
  • EchoKG – echocardiogram
  • Magnetocardiography (MCG)

Heart Activity Measurements

ekg ecg electrocardiogram
EKG/ECG -- electrocardiogram

Williem Einthoven: in 1924 Nobel prize

ECK -- electrocardiogram

slide8
ATRIUM

VENTRICLE

ECK -- electrocardiogram

the conduction system of the heart
The conduction system of the heart.

ECK -- electrocardiogram

animation of a normal ekg wave
Animation of a normal EKG wave

ECK -- electrocardiogram

information from ekg
Information from EKG
  • If the electric or muscular function of the heart is disturbed for some reason, it will affect how the electric signals spread through the heart muscle.

ECK -- electrocardiogram

slide13
The heart's electrical axis refers to the general direction of the heart's depolarization wavefront (or mean electrical vector) in the frontal plane.

Lead I.

Lead III.

Lead II.

ECK -- electrocardiogram

slide14
EKG
  • These three bipolar limb leads roughly form an equilateral triangle (with the heart at the center) that is called Einthoven's triangle in honor of Willem Einthoven who developed the electrocardiogram in 1901.

ECK -- electrocardiogram

negative electrode on the right arm and the positive electrode on the left arm
Different directions during the EKG measurementNegative electrode on the right arm and the positive electrode on the left arm

Negative electrode on the right arm and the positive electrode on the left leg.

Negative electrode on the left arm and the positive electrode on the left leg.

Maximal positive deflection is obtained in lead III when the depolarization wave

travels parallel to the axis between the left arm and left leg.

ECK -- electrocardiogram

slide17
The realtively small P

wave is produced by

electrical currents

generated just before

contraction of the atria

EKG

Accoustic

QRS complex is caused by

currents generated in the

ventricles during depolarization

just prior to venticular contraction.

R is the most prominent

component of this wave complex.

ECK -- electrocardiogram

slide18
160 ms

300 ms

370 ms

ECK -- electrocardiogram

830 ms

slide19
positive

deflection

on the ECG

negative

deflection

on the ECG

equiphasic

complex

deflection

on the ECG

External snap

Snap coated with Ag/AgCl

Gel soaked sponge

Adhesive layer

ECK -- electrocardiogram

the ecg system
The ECG system

Instrumentation amplifier, which has a very high CMRR (90dB) (common-mode rejection ratio)

and high gain (1000), with power supply +9V and -9V.

An opto-coupler to isolate

the In-Amp and Output.

A transducer AgCl electrode,

which convert ECG into electrical voltage.

The voltage is in the range of 1 mV ~ 5 mV

Bandpass filter of 0.04 Hz to

150 Hz filter. It’s implemented

by cascading a low-pass filter

and a high pass filter

ECK -- electrocardiogram

heart activity measurements22
Heart Activity Measurements
  • Pulse rate
  • ECG/EKG – electrocardiogram
  • Impedance cardiogram, IKG -- impedance cardiography
  • EchoKG – echocardiogram
  • Magnetocardiography (MCG)

Heart Activity Measurements

impedance cardiogram
Impedance cardiogram

Impedance changes

Differentiatior

Amplifier

dZ/dt

Z0 value is the total impedance

between the two inner leads

High-frequency = 40-100 KHz

Constant current = 4 mA

Impedance cardiogram

impedance cardiogram24
Impedance cardiogram

R-Z is the time interval from

the R wave of the ECG to

maximum ejection as indicated

by the peak of dZ/dt

ventricular ejection time

Impedance cardiogram

slide25
Part of automated external defibrillator
  • Investigate circulatory system problems: valve defects, right-left shunting, congestive failure
  • Impedance of the thorax can be considered to be divided into two parts:
    • the impedance of both tissue and fluids
    • the amount and distribution of blood The amount of blood in the thorax changes as a function of the heart cycle. The changes in the distribution of blood in the thorax as a function of the heart cycle can be determined by measuring the impedance changes of the thorax.

Band electrodes

ECK -- electrocardiogram

heart activity measurements26
Heart Activity Measurements
  • Pulse rate
  • ECG/EKG – electrocardiogram
  • Impedance cardiogram, IKG -- impedance cardiography
  • EchoKG – echocardiogram
  • Magnetocardiography (MCG)

Heart Activity Measurements

slide27
EchoKG

Echocardiogram

Ultrasound waves: 2.5–18 MHz

EchoKG -- Echocardiogram

echokg echocardiogram
EchoKG -- Echocardiogram

EchoKG -- Echocardiogram

transducer
Transducer

EchoKG -- Echocardiogram

40 khz ultrasound receiver
40 kHz Ultrasound receiver

A X100 transistor amplifier is followed by a zero cross detector circuit, using a

voltage comparator. The output is a TTL logic signal, corresponding to the

received 40KHz signal.

ECK -- electrocardiogram

medium power 40khz ultrasound transducer driver
Medium Power 40KHz Ultrasound Transducer Driver

This crystal controlled circuit drives a 40KHz piezoelectric transducer with a 30v peak to peak signal.

ECK -- electrocardiogram

heart activity measurements33
Heart Activity Measurements
  • Pulse rate
  • ECG/EKG – electrocardiogram
  • Impedance cardiogram, IKG -- impedance cardiography
  • EchoKG – echocardiogram
  • Magnetocardiography (MCG)

Heart Activity Measurements

dc squids
dc SQUIDs

Scanning electron micrograph of the SQUID ring with step-edge Josephson junctions.

  • Magnetometers based on dc SQUIDs are currently the most sensitive sensors for magnetic fields, achieving a magnetic field resolution which is about a billion times below the earth's magnetic field.
  • A dc SQUID basically consists of a superconducting ring interrupted by two weak links called Josephson junctions.
  • SQUID can be viewed as a flux-to-voltage converter.

ECK -- electrocardiogram

noise spectrum of the magnetic field
Noise spectrum of the magnetic field

noise in an industrial environment,

measured with an unshielded

multiloop magnetometer

The magnetometer's

intrinsic noise level is

several orders of magnitude lower.

ECK -- electrocardiogram

dc squids38
dc SQUIDs

A multiloop SQUID magnetometer. The diameter of this device is 8.5 mm.

  • The SQUID ring itself is enlarged and it consists of several identical pickup loops, which are connected in parallel to reduce the inductance. The 16 loops are arranged to the cart-wheel like shape of the device. A multilayer technology is needed for the preparation.

ECK -- electrocardiogram

block diagram of a squid magnetometer
Block diagram of a SQUID magnetometer

transform the applied

flux into a room temperature

voltage output

senses changes in the

external magnetic field

and transforms them

into an electrical current

acquiring, storing

analyzing data

transforms the resulting

current into a magnetic

flux in the SQUID sensor

ECK -- electrocardiogram

68 channel dc squid system
68-channel dc-SQUID system

SQUID maps the axial (BZ) component

ECK -- electrocardiogram

real time magnetocardiogram recorded with a multiloop magnetometer
Real-time magnetocardiogram recorded with a multiloop magnetometer.

ECK -- electrocardiogram

magnetocardiography mcg
Magnetocardiography (MCG)
  • Magnetic field: x, y, z component
  • Grid measurement
  • Similar sensitivity to EKG
  • Higher SNR than EKG

Magnetocardiography (MCG)

slide43
magnode

Solenoid coil

Ir = reciprocal current

ΦLM = reciprocal magnetic scalar potential field

HLM = reciprocal magnetic field

BLM = reciprocal magnetic induction field

ELM = reciprocal electric field

JLM = lead field  

VLM = voltage in the lead due to the volume source i in the volume conductor  

Magnetocardiography (MCG)

slide44
Measurement of the x-component

of the magnetic heart vector

The general construction of

the measurement system

Baule-McFee lead system

Measurement of the z-component

of the magnetic heart vector

Measurement of the y-component

of the magnetic heart vector

Magnetocardiography (MCG)

unipolar bipolar measurement locations on the anterior and posterior sides
Unipolar & Bipolar measurement locations on the anterior and posterior sides

ECK -- electrocardiogram

schematic illustration of the generation of the x component of the mcg signal
Schematic illustration of the generation of the x component of the MCG signal.

ECK -- electrocardiogram

advantages
Advantages
  • Insulating barriers such as the skull, varying layers of tissue, anatomical open spaces, do not attenuate or distort magnetic fields. The magnetic permeability of the tissue = free space. Therefore the sensitivity of the MCG is not affected by the high electric resistivity of lung tissue.
  • different sensitivity distribution with EKG
  • the magnetic detector is not in contact with the subject
  • SQUID magnetometer is readily capable of measuring DC signals. Such signals can be obtained electrically only with great difficulty.

Magnetocardiography (MCG)

disadvantages
Disadvantages
  • ECG is easier to use
  • Technologically more complicated, requires complex and expensive equipment: SQUID magnetometer, liquid helium, and a low-noise environment
  • Because of the development of the SQUID technology, a shielded room is no longer needed in magnetocardiography.
  • Future: at the liquid nitrogen temperature which decreases the operational costs

Magnetocardiography (MCG)

references
References
  • MCG:
    • http://butler.cc.tut.fi/~malmivuo/bem/bembook/20/20.htm
    • http://www.kreynet.de/asc/squids.html
  • EchoKG:
    • http://www.heartsite.com/html/echocardiogram.html#what_US
    • http://www.discovercircuits.com/DJ-Circuits/ultra40khzxtr1.htm
  • EKG
    • http://en.wikipedia.org/wiki/Electrocardiogram
    • http://www.ecglibrary.com/
    • http://www.americanheart.org/presenter.jhtml?identifier=3005172
    • http://www.medmovie.com/mmdatabase/MediaPlayer.aspx?ClientID=68&TopicID=600
    • John L. Andreassi: Psychophysiology
    • http://www.cisl.columbia.edu/kinget_group/student_projects/ECG%20Report/E6001%20ECG%20final%20report.htm
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