LEC 3 Flashcards
اماكن بقدر اقيس منها كهربية الجسم
EEG of the brain, &electrical activity of the muscles), but the heart is the greatest electrical activity,
Einthoven’s method
3 Lead
2 arm
1 left leg
lead 1
Connecting the right arm with the left arm
lead 2
Connecting the right arm with the left leg
lead 3
Connecting the left arm with the left leg
first 3 leads are
bipolar leads
bipolar leads records
difference between these two points
unipolar leads measure
the potential of only one point
The maximum voltage must be within
lead 2, because it is parallel to the direction of the current (base to apex).
The bipolar leads can be used to diagnose
different cardiac arrhythmias abnormalities in the period of times between different waves of the cycle.
(if it’s prolonged or shortened).
Chest leads are used in diagnose
abnormalities in the waves themselves e.g. QRS
V1 Place
fourth intercostal space to the right of the sternum
V2 Place
fourth intercostal space to the left of the sternum.
V4 Place
fifth intercostal space in the left midclavicular line.
just beneath the nipple.
V3 Place
in between V2 and V4
V5 Place
anterior axillary line within fifth intercostal space.
V6 Place
middle axillary line within fifth intercostal space.
V1 Related part in heart
Right ventricle
V2 Related part in heart
The sputum between the ventricles.
V3 Related part in heart
Anterior of the left ventricle
V4 Related part in heart
Anteroseptal aspect of the left ventricle.
V5 Related part in heart
Anterolateral aspect of the left ventricle
V6 Related part in heart
Lateral aspect of the left ventricle
IN chest leads The sign of current depends on
where we put the electrodes and the direction of the current.
These chest leads help us in
myocardial infraction patients to identify which part is
affected by the infraction.
12 leads are divided into
- Bipolar leads: (also called bipolar limb lead):
which includes: lead I, lead II, and lead III. - Unipolar leads: which are subdivided into:
A. unipolar limp leads: (AVR, AVL & AVF).
B. unipolar chest leads: (V1, V2, V3, V4, V5 and V6).
what we are examining in AVF
the inferior part of the left ventricle.
The first part of the ventricle that will be excited is
direction of excitation
the base of the septum
is from the left to the right,
Q wave → negative . why → to the RT and the current is to the LF
and from endocardium to the epicardium (from inside to the outside).
the second part of the the ventricle that will be excited is
Base of the septum → apex → lateral wall
benefits of the the presence of Purkinje fibers
excitation of apex to the lateral wall develop in a very short period of time
30 milliseconds لشو هاي
excitation from SA node to AV node and the time for depolarization of both of the atria)
130 milliseconds لشو هدول
delay in the av node
60ms
ventricles excitation
220 milliseconds.
excitation to start in the SA node until the stimulation of both ventricles
PR segment
from the end of p wave to the beginning of QRS)
The PR segment is called
isoelectric line
2 things happen at the same tim
atrial repolarization and the depolarization of ventricle
how to see the repolarization of atria
put a catheter on the atria, stimulate it and see the repolarization.
Intervals in ECG
- PR interval
2) QT interval
3) TP interval
PR interval represents
duration of the impulse to start in the SA node until it
reaches the ventricles (including the delay that happens in the AV node).
PR interval كم تشتغرق من الوقت
160 millisecond
120 to 200 millisecond.
PR interval includes
depolarization of atria &the plateau of atria.
the relationship between PR interval and heart rate
عكسية
When we are sleeping: the heart rate decreases, so the PR interval will
increase.
When we do exercise, anxiety: the heart rate will increase, so the PR
interval will be shorter.
QT interval represents
the AP of the ventricles
depolarization, plateau and repolarization of
the ventricles
QT interval كم تستغرق من الوقت
350 milliseconds
QT interval in myocardial infarction) & angina
increasedbecause the wash out of ions will be abnormal {problem in the sodium potassium pump})
TP interval time represents
the resting potential,
interval that all channels is closed
TP interval
interval that represents the resting potential
TP interval
during TP interval
leakage of the Na in the SA node, not in the ventricles or atria, waiting for the threshold to be reached to the next beat. (
isoelectric lines
PR segment, ST segment and TP
interval
R wave
depolarization of the lateral wall of the
ventricles)
Qwave
depolarization of the base of the septum
the right side
S increase and R decreased
the left side
R↑
S ↓
Small R and large S
in V1
R will be at the maximum
V6 left side
R Will be at the minimum
V1 or V2 right side
S will be at the maximum
V 1or V2 right side
S at minimum in
V6
waves in AVR are
negative
why is T wave positive
the direction of repolarization of the ventricles starts from the outside to the inside
