Transcript PRACTICAL 2 : ELECTROCARDIOGRAM (ECG/EKG)

PRACTICAL 2 :
ELECTROCARDIOGRAM
(ECG/EKG)
By.Mohamad Azmir bin Azizan
Medical lab technologist
Faculty of Medicine UiTM
What is an electrocardiogram?
• An electrocardiogram or 'ECG' records the electrical
activity of the heart. The heart produces tiny
electrical impulses which spread through the heart
muscle to make the heart contract.
• These impulses can be detected by the ECG machine.
You may have an ECG to help find the cause of
symptoms such as palpitations or chest pain.
Sometimes it is done as part of routine tests, for
example, before you have an operation.
• The ECG test is painless and harmless. (The ECG
machine records electrical impulses coming from your
body - it does not put any electricity into your body
How is it done?
• Small metal electrodes are stuck onto your arms, legs
and chest.
• Wires from the electrodes are connected to the ECG
machine.
• The machine detects and amplifies the electrical
impulses that occur each heartbeat and records them
onto a paper or computer.
• A few heartbeats are recorded from different sets
of electrodes. The test takes about five minutes to
do.
What does an ECG show?
• The electrodes on the different parts of the body
detect electrical impulses coming from different
directions within the heart. There are normal
patterns for each electrode. Various heart disorders
produce abnormal patterns. The heart disorders that
can be detected include:
• Abnormal heart rhythms. If the heart rate is very
fast, very slow, or irregular. There are various types
of irregular heart rhythm with characteristic ECG
patterns.
• A heart attack, and if it was recent or some time ago.
A heart attack causes damage to heart muscle, and
heals with scar tissue. These can be detected by
abnormal ECG patterns.
• An enlarged heart. Basically this causes bigger
impulses than normal.
Understanding ECG recording
•
•
Each conventional ECG tracing records from :
bipolar leads (2 opposite points) consisting of lead
I, II, III and
•
(ii) unipolar leads i.e. aVR, aVL, aVF, V1, V2, V3,
V4, V5 and V6.
Bipolar leads
•
All the bipolar leads measure the potential
difference between 2 points namely :
•
lead I between right arm (RA) and the left arm
(LA).
•
lead II between RA and left leg (LL).
•
lead III between LA and LL.
Procedure
• Students are to be chosen as subjects for
ECG recording.
• Ask the subject to lie on the couch/table.
• Clean the skin of the arms and legs with
alcohol provided.
• Apply electrolyte or electrode cream/jelly on
the surface of the electrodes and to the skin
where electrodes will be placed.
• Secure the electrodes to the arms or legs
using rubber straps.
Recording standard lead I, II and III
• Set up the electrodes on the subject’s arms and legs
as follows (see Figure)
– RA electrode on the right arm.
– LA electrode on the left arm.
– LF/LL electrode on the left leg.
– Earth/ground electrode on the right leg.
• Set up the physiograph using channel II with paper
speed of 2.5 cm/second and calibrate the recording
pen at 1.0 mV/cm.
• Record 5 heart beats from each lead : I, II and III.
• Without changing the position of the electrodes,
change the knob on the physiograph to record
unipolar lead aVR, aVL and aVF.
• Record 5 heart beats from each lead : aVR, aVL and
aVF.
• To do the chest lead, ask the subject to undress the
upper body to expose the chest.
• Locate the anatomical parts of the subject’s chest
V1 – right margin of the
sternum at the 4th
intercoastal space.
V2 – left margin of the
sternum at the 4th
intercoastal space.
V3 – midway between V2 and
V4.
V4 – 5th intercostals space at
left
midclavicular line.
V5 – 5th intercoastal space
at left midaxillary line.
V6 – 5th intercoastal space
at left midaxillary line.
Mid-Clavicular line
Nurse import ni
Mid-Clavicular line
LEFT ARM
RIGHT ARM
LEFT LEG
RIGHT LEG
Lead I
- Lead I +
Lead II
Lead III
Lead II
+
Lead III
+
Locations of standard lead I, II, III and chest leads for ECG recording
Officer yg verify
result patient
Patient dah bgn
nak tgk result
Azmir n faizal try do
the best
Mrs. Sham (profesional ECG
technician)
Graf appears here
ECG pinjam CTC
How to interpret ECG tracing
The normal ECG
Drawing of the EKG, with labels of
intervals
P=P wave, PR=PR segment, QRS=QRS
complex, QT=QT interval, ST=ST
segment, T=T wave.
Electrocardiogram of a healthy man,
A typical ECG tracing of a normal
heartbeat consists of a P wave, a
QRS complex and a T wave. A small
U wave is not normally visible.
Axis
• The axis is the general direction of the electrical
impulse through the heart. It is usually directed to
the bottom left, although it can deviate to the right
in very tall people and to the left in obesity. Extreme
deviation is abnormal and indicates a bundle branch
block, ventricular hypertrophy or (if to the right)
pulmonary embolism. It also can diagnose
dextrocardia or a reversal of the direction in which
the heart faces, but this condition is very rare and
often has already been diagnosed by something
else(such as a chest x-ray).
P wave
• The P wave is the electrical signature of the current
that causes atrial contraction. Both the left and right
atria contract simultaneously. Irregular or absent P
waves may indicate arrhythmia. Its relationship to
QRS complexes determines the presence of a heart
block.
QRS
• The QRS complex corresponds to the current that
causes contraction of the left and right ventricles,
which is much more forceful than that of the atria
and involves more muscle mass, thus resulting in a
greater ECG deflection.
• The Q wave, when present, represents the small
horizontal (left to right) current as the action
potential travels through the interventricular septum.
Very wide and deep Q waves do not have a septal
origin, but indicate myocardial infarction.
• The R and S waves indicate contraction of the
myocardium. Abnormalities in the QRS complex may
indicate bundle branch block (when wide), ventricular
origin of tachycardia, ventricular hypertrophy or
other ventricular abnormalities. The complexes are
often small in pericarditis..
T wave
• The T wave represents the repolarization of the
ventricles. The QRS complex usually obscures the
atrial repolarization wave so that it is not usually
seen. Electrically, the cardiac muscle cells are like
loaded springs. A small impulse sets them off, they
depolarize and contract. Setting the spring up again is
repolarization (more at action potential).
• In most leads, the T wave is positive. Negative T
waves can be signs of disease, although an inverted T
wave is normal in V1 (and V2-3 in black people).
• The ST segment connects the QRS complex and the
T wave. It can be depressed in ischemia and elevated
in myocardial infarction, and downslopes in digoxin
use.
• T wave abnormalities may indicate electrolyte
disturbance, such as hyperkalemia
SEKIAN