apps of electrostatistics
TRANSCRIPT
Electrocardiography
Cells in humans act like little batteries These cells have different ion concentrations inside and outside of their membranes which create small electric potentials called biopotentials When there is a disturbance in a biopotential this gives rise to an action potential which is the depolarization and repolarization of the cell
Essentially the action
potentials from different
nodes in the heart are
what make up
electrocardiograph (ECG)
signals
ECG signals are
comprised of the
superposition of the
different action potentials
from the heart beating as
shown in Figure
ECG machines use
electrodes to convert the
ionic signals from the
body into electrical
signals to be displayed
and used for data analysis
However due to the size of the signals and outside noise ECG requires amplification and
filtering to produce high quality signals
Leads and what
they tell you
Each lead can be thought of as
lsquolooking atrsquo an area
of myocardium
Chest leads
V1 to V6 lsquolook rsquo at the heart on
the transverse plain
1048707
V1 and V2 look at the anterior
of the heart and R ventricle
1048707
V3 and V4 = anterior and septal
1048707
V5 and V6 = lateral and left
ventricle
Electrode label (in the USA) Electrode placement
RA On the right arm avoiding thick muscle
LA In the same location where RA was placed but on the left arm
RL On the right leg lateral calf muscle
LL In the same location where RL was placed but on the left leg
V1 In the fourth intercostal space (between ribs 4 and 5) just to the right of the sternum
V2 In the fourth intercostal space (between ribs 4 and 5) just to the left of the sternum
V3 Between leads V2 and V4
V4 In the fifth intercostal space (between ribs 5 and 6) in the mid-clavicular line
V5 Horizontally even with V4 in the left anterior axillary line
V6 Horizontally even with V4 and V5 in the mid axillary line
The ECG measures
differences in the
electric potential V
VE
The Electric Potential is the Potential ability to do
work
Alternatively Work = Q V
Where V = 21 VV
For uniform electric fields dEVd
VE ||||
Electric Potential
bull Interior of Heart muscle cells are negatively
charged at rest
bull Called ldquopolarisationrdquo
bull K+ ions leak out leaving interior ndashve
bull Depolarisation occurs just proir to
contraction
Na+ ions enter cells
Occurs in waves across the heart
Re-polarisation restores ndashve charge in
interior
+ + + + - - - - -+ +
+ +
- -
- -
Polarisation Depolarisation
ECG
Works by
measuring changes
in electric field as
heart pumps
Heart can be
modeled as a
rotating dipole
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
Cells in humans act like little batteries These cells have different ion concentrations inside and outside of their membranes which create small electric potentials called biopotentials When there is a disturbance in a biopotential this gives rise to an action potential which is the depolarization and repolarization of the cell
Essentially the action
potentials from different
nodes in the heart are
what make up
electrocardiograph (ECG)
signals
ECG signals are
comprised of the
superposition of the
different action potentials
from the heart beating as
shown in Figure
ECG machines use
electrodes to convert the
ionic signals from the
body into electrical
signals to be displayed
and used for data analysis
However due to the size of the signals and outside noise ECG requires amplification and
filtering to produce high quality signals
Leads and what
they tell you
Each lead can be thought of as
lsquolooking atrsquo an area
of myocardium
Chest leads
V1 to V6 lsquolook rsquo at the heart on
the transverse plain
1048707
V1 and V2 look at the anterior
of the heart and R ventricle
1048707
V3 and V4 = anterior and septal
1048707
V5 and V6 = lateral and left
ventricle
Electrode label (in the USA) Electrode placement
RA On the right arm avoiding thick muscle
LA In the same location where RA was placed but on the left arm
RL On the right leg lateral calf muscle
LL In the same location where RL was placed but on the left leg
V1 In the fourth intercostal space (between ribs 4 and 5) just to the right of the sternum
V2 In the fourth intercostal space (between ribs 4 and 5) just to the left of the sternum
V3 Between leads V2 and V4
V4 In the fifth intercostal space (between ribs 5 and 6) in the mid-clavicular line
V5 Horizontally even with V4 in the left anterior axillary line
V6 Horizontally even with V4 and V5 in the mid axillary line
The ECG measures
differences in the
electric potential V
VE
The Electric Potential is the Potential ability to do
work
Alternatively Work = Q V
Where V = 21 VV
For uniform electric fields dEVd
VE ||||
Electric Potential
bull Interior of Heart muscle cells are negatively
charged at rest
bull Called ldquopolarisationrdquo
bull K+ ions leak out leaving interior ndashve
bull Depolarisation occurs just proir to
contraction
Na+ ions enter cells
Occurs in waves across the heart
Re-polarisation restores ndashve charge in
interior
+ + + + - - - - -+ +
+ +
- -
- -
Polarisation Depolarisation
ECG
Works by
measuring changes
in electric field as
heart pumps
Heart can be
modeled as a
rotating dipole
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
Essentially the action
potentials from different
nodes in the heart are
what make up
electrocardiograph (ECG)
signals
ECG signals are
comprised of the
superposition of the
different action potentials
from the heart beating as
shown in Figure
ECG machines use
electrodes to convert the
ionic signals from the
body into electrical
signals to be displayed
and used for data analysis
However due to the size of the signals and outside noise ECG requires amplification and
filtering to produce high quality signals
Leads and what
they tell you
Each lead can be thought of as
lsquolooking atrsquo an area
of myocardium
Chest leads
V1 to V6 lsquolook rsquo at the heart on
the transverse plain
1048707
V1 and V2 look at the anterior
of the heart and R ventricle
1048707
V3 and V4 = anterior and septal
1048707
V5 and V6 = lateral and left
ventricle
Electrode label (in the USA) Electrode placement
RA On the right arm avoiding thick muscle
LA In the same location where RA was placed but on the left arm
RL On the right leg lateral calf muscle
LL In the same location where RL was placed but on the left leg
V1 In the fourth intercostal space (between ribs 4 and 5) just to the right of the sternum
V2 In the fourth intercostal space (between ribs 4 and 5) just to the left of the sternum
V3 Between leads V2 and V4
V4 In the fifth intercostal space (between ribs 5 and 6) in the mid-clavicular line
V5 Horizontally even with V4 in the left anterior axillary line
V6 Horizontally even with V4 and V5 in the mid axillary line
The ECG measures
differences in the
electric potential V
VE
The Electric Potential is the Potential ability to do
work
Alternatively Work = Q V
Where V = 21 VV
For uniform electric fields dEVd
VE ||||
Electric Potential
bull Interior of Heart muscle cells are negatively
charged at rest
bull Called ldquopolarisationrdquo
bull K+ ions leak out leaving interior ndashve
bull Depolarisation occurs just proir to
contraction
Na+ ions enter cells
Occurs in waves across the heart
Re-polarisation restores ndashve charge in
interior
+ + + + - - - - -+ +
+ +
- -
- -
Polarisation Depolarisation
ECG
Works by
measuring changes
in electric field as
heart pumps
Heart can be
modeled as a
rotating dipole
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
Leads and what
they tell you
Each lead can be thought of as
lsquolooking atrsquo an area
of myocardium
Chest leads
V1 to V6 lsquolook rsquo at the heart on
the transverse plain
1048707
V1 and V2 look at the anterior
of the heart and R ventricle
1048707
V3 and V4 = anterior and septal
1048707
V5 and V6 = lateral and left
ventricle
Electrode label (in the USA) Electrode placement
RA On the right arm avoiding thick muscle
LA In the same location where RA was placed but on the left arm
RL On the right leg lateral calf muscle
LL In the same location where RL was placed but on the left leg
V1 In the fourth intercostal space (between ribs 4 and 5) just to the right of the sternum
V2 In the fourth intercostal space (between ribs 4 and 5) just to the left of the sternum
V3 Between leads V2 and V4
V4 In the fifth intercostal space (between ribs 5 and 6) in the mid-clavicular line
V5 Horizontally even with V4 in the left anterior axillary line
V6 Horizontally even with V4 and V5 in the mid axillary line
The ECG measures
differences in the
electric potential V
VE
The Electric Potential is the Potential ability to do
work
Alternatively Work = Q V
Where V = 21 VV
For uniform electric fields dEVd
VE ||||
Electric Potential
bull Interior of Heart muscle cells are negatively
charged at rest
bull Called ldquopolarisationrdquo
bull K+ ions leak out leaving interior ndashve
bull Depolarisation occurs just proir to
contraction
Na+ ions enter cells
Occurs in waves across the heart
Re-polarisation restores ndashve charge in
interior
+ + + + - - - - -+ +
+ +
- -
- -
Polarisation Depolarisation
ECG
Works by
measuring changes
in electric field as
heart pumps
Heart can be
modeled as a
rotating dipole
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
Electrode label (in the USA) Electrode placement
RA On the right arm avoiding thick muscle
LA In the same location where RA was placed but on the left arm
RL On the right leg lateral calf muscle
LL In the same location where RL was placed but on the left leg
V1 In the fourth intercostal space (between ribs 4 and 5) just to the right of the sternum
V2 In the fourth intercostal space (between ribs 4 and 5) just to the left of the sternum
V3 Between leads V2 and V4
V4 In the fifth intercostal space (between ribs 5 and 6) in the mid-clavicular line
V5 Horizontally even with V4 in the left anterior axillary line
V6 Horizontally even with V4 and V5 in the mid axillary line
The ECG measures
differences in the
electric potential V
VE
The Electric Potential is the Potential ability to do
work
Alternatively Work = Q V
Where V = 21 VV
For uniform electric fields dEVd
VE ||||
Electric Potential
bull Interior of Heart muscle cells are negatively
charged at rest
bull Called ldquopolarisationrdquo
bull K+ ions leak out leaving interior ndashve
bull Depolarisation occurs just proir to
contraction
Na+ ions enter cells
Occurs in waves across the heart
Re-polarisation restores ndashve charge in
interior
+ + + + - - - - -+ +
+ +
- -
- -
Polarisation Depolarisation
ECG
Works by
measuring changes
in electric field as
heart pumps
Heart can be
modeled as a
rotating dipole
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
The ECG measures
differences in the
electric potential V
VE
The Electric Potential is the Potential ability to do
work
Alternatively Work = Q V
Where V = 21 VV
For uniform electric fields dEVd
VE ||||
Electric Potential
bull Interior of Heart muscle cells are negatively
charged at rest
bull Called ldquopolarisationrdquo
bull K+ ions leak out leaving interior ndashve
bull Depolarisation occurs just proir to
contraction
Na+ ions enter cells
Occurs in waves across the heart
Re-polarisation restores ndashve charge in
interior
+ + + + - - - - -+ +
+ +
- -
- -
Polarisation Depolarisation
ECG
Works by
measuring changes
in electric field as
heart pumps
Heart can be
modeled as a
rotating dipole
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
bull Interior of Heart muscle cells are negatively
charged at rest
bull Called ldquopolarisationrdquo
bull K+ ions leak out leaving interior ndashve
bull Depolarisation occurs just proir to
contraction
Na+ ions enter cells
Occurs in waves across the heart
Re-polarisation restores ndashve charge in
interior
+ + + + - - - - -+ +
+ +
- -
- -
Polarisation Depolarisation
ECG
Works by
measuring changes
in electric field as
heart pumps
Heart can be
modeled as a
rotating dipole
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
Depolarisation begins at the SA node
The wave of depolarisation spreads across the atria
It reaches the AV node and the accessory bundle
Conduction is delayed as usual by the in-built delay in the AV node
However the accessory bundle has no such delay and depolarisation begins
early in the part of the ventricle served by the bundle
As the depolarisation in this part of the ventricle does not travel in the high
speed conduction pathway the spread of depolarisation across the ventricle is
slow causing a slow rising delta wave
Until rapid depolarisation resumes via the normal pathway and a more
normal complex follows
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection
How does the ECG work
1048707
Electrical impulse (wave of depolarisation) picked
up by placing electrodes on patient
1048707
The voltage change is sensed by measuring the
current change across 2 electrodes ndash a positive
electrode and a negative electrode
1048707If the electrical impulse travels towards the
positive electrode this results in a positive
deflection
1048707
If the impulse travels away from the positive
electrode this results in a negative deflection