2. The issue to be discussed
• What is an electrocardiogram?
• Why might we need an electrocardiogram?
• How do we get ready for an electrocardiogram?
• Ecg taking process
• 12-lead ECG electrode placement
• Electrical Conduction System of the Heart
• ECG Nomenclature
• ECG Interpretation
• Assessment of rhythm, calculating heart rate.
• observing P-wave forms
• measurement and interpretation of ECG intervals and segments.
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3. What is ECG?
An electrocardiogram, abbreviated as ECG or EKG, is a measurement of the
electrical activity of the heart during the cardiac cycle and can be used to
identify if there are any issues with the normal functioning of the heart.
An electrocardiogram (ECG) is one of the simplest and fastest tests used to
evaluate the heart. Electrodes (small, plastic patches that stick to the skin) are
placed at certain spots on the chest, arms, and legs
ECG conveys a large amount of information about the structure of the heart
and the function of its electrical conduction system.
Risks
An electrocardiogram is a safe procedure. There is no risk of electrical shock
during the test because the electrodes used do not produce electricity. The
electrodes only record the electrical activity of the heart.
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4. Why might we need an electrocardiogram?
Some reasons for your doctor to request an electrocardiogram (ECG) include:
• To look for the cause of chest pain
• To evaluate problems which may be heart-related, such as severe tiredness, shortness
of breath, dizziness, or fainting
• To identify irregular heartbeats
• To help determine the overall health of the heart before procedures such as surgery; or
after treatment for conditions such as a heart attack (myocardial infarction, or MI),
endocarditis (inflammation or infection of one or more of the heart valves); or after
heart surgery or cardiac catheterization
• To see how an implanted pacemaker is working
• To determine how well certain heart medicines are working
• To get a baseline tracing of the heart's function during a physical exam; this may be
used as a comparison with future ECGs, to determine if there have been any changes
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5. The history of ECG machine
• In 1903 Willem Einthoven
a Dutch doctor and
physiologist invented the
first practical
electrocardiogram.
• He received the Nobel
prize in medicine in 1924
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NOW
Modern ECG machine has involved compact
electronic system that often include computerized
interpretation of the electrocardiogram
6. Generally, an ECG follows this process:
• Remove any jewelery or other objects that may interfere with the test.
• Remove upper clothing so that electrodes can be attached to the chest and limbs.
• Electrodes are attached to arms, legs and chest with a sticky gel. Electrodes work
best with clean, dry and oil or lotion-free skin
• If chest, arms, or legs are very hairy, the technician may shave or clip small
patches of hair, as needed, so that the electrodes will stick closely to the skin.
• It will be important for you to lie still and not talk during the ECG.
• Once the leads are attached, the technician may enter identifying information
about patient into the machine's computer.
• The ECG will be started. It will take only a short time for the tracing to be
completed.
• Once the tracing is completed, the technician will disconnect the leads and
remove the skin electrodes
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7. Parts of an ECG
The standard ECG has 12 leads. Six of the leads are considered “limb leads”
because they are placed on the arms and/or legs of the individual. The other six
leads are considered “precordial leads” because they are placed on the torso
(precordium).
• The six limb leads are called lead I, II, III, aVL, aVR and aVF. The letter “a” stands
for “augmented,” as these leads are calculated as a combination of leads I, II and
III.
• The six precordial leads are called leads V1, V2, V3, V4, V5 and V6
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8. Limb (Extremity) Electrodes and Placement
• RA (Right Arm) – Anywhere
between the right shoulder and
right elbow
• RL (Right Leg) – Anywhere below
the right torso and above the
right ankle
• LA (Left Arm) – Anywhere
between the left shoulder and
the left elbow
• LL (Left Leg) – Anywhere below
the left torso and above the left
ankle
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12-lead ECG electrode placement
9. Chest (Precordial) Electrodes and Placement
• V1 – Fourth intercostal space on the right
sternum
• V2 – Fourth intercostal space at the left
sternum
• V3 – Midway between placement of V2 and
V4
• V4 – Fifth intercostal space at the
midclavicular line
• V5 – Anterior axillary line on the same
horizontal level as V4
• V6 – Mid-axillary line on the same horizontal
level as V4 and V5
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10. Right sided 12-lead ECG placement
• a right sided 12-lead ECG
placement allows you to
detect a right sided infarct.
• At a minimum, lead V4
should be placed on the 5th
intercostal, mid-clavicular
(exact opposite of the regular
left side placement) if an
inferior infarct was originally
seen in leads II, III, and AVF.
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11. Electrical Conduction System of the
Heart
Cells in the cardiac conduction system can generate electrical
impulses and then distribute the signal throughout your heart.It’s
also known as your heart’s electrical system.
The parts of the cardiac conduction system
• The sinoatrial (SA) node.
• The atrioventricular (AV) node.
• The Bundle of His.
• Bundle branches.
• Purkinje fibers.
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12. ECG tracings are recorded on grid paper.
• The horizontal axis of the
EKG paper records time, with black marks at the top indicating 3-second intervals.
• Each second is marked by 5 large grid blocks. Thus, each large block equals 0.2
second. The vertical axis records EKG amplitude (voltage). Two large blocks equal 1
millivolt (mV). Each small block equals 0.1 mV.
• Within the large blocks are 5 small blocks, each representing 0.04 seconds.
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13. ECG Nomenclature
Normal EKG tracings consist of waveform components that indicate electrical events during one heart beat. These waveforms are
labeled P, Q, R, S, T and U.
• P wave is the first deflection and is normally a positive (upward) waveform. It indicates atrial depolarization.
• QRS complex follows the P wave. It normally begins with a downward deflection, Q; a larger upward deflection, R; and then a
downward S wave. The QRS complex represents ventricular depolarization and contraction.
• T wave is normally a modest upward waveform, representing ventricular repolarization.
• U wave indicates the recovery of the Purkinje conduction fibers. This wave component may not be observable.
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14. ECG interpretation should be performed using a standard
procedure. For this course, we are using an eight-step procedure
• Rhythm
• Rate
• P Wave
• PR Interval
• QRS Interval
• T Wave
• QT Interval
• ST Segment
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15. ECG Rhythm
• For ventricular rhythms, examine the R to R intervals on the EKG strip. Calipers or paper
marks can be used to fix the distance for one R-R interval and then this distance can be
compared to other R-R pairs.
• Are they regular, meaning that each heart beat's R-R interval is equal?
Small variations of up to 10% are considered equal. in cases of respiratory sinus arrhythmia is not
harmful, the P-P interval and heart rate relates to their breathing cycle.
• Is the rhythm irregular?
• For atrial rhythm, observe the P-P intervals. Are they regular (minor variations can be caused
by the breath cycle)? If P-P intervals are irregular, is there a pattern?
• Asystole is when there’s no electricity or movement in your heart.
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16. Heart Rate
• There are several methods for determining heart rate. Our first method is simple.
Count the number of QRS complexes over a 6-second interval. Multiply by 10 to
determine heart rate. This method works well for both regular and irregular
rhythms.
• The second method uses small boxes. Count the number of small boxes for a
typical R-R interval. Divide this number into 1500 to determine heart rate. In the
second image, the number of small boxes for the R-R interval is 21.5. The heart
rate is 1500/21.5, which is 69.8.
• Count the number of LARGE boxes for a typical R-R interval. Divide this number
into 300 to determine heart rate.
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18. Sinus tachycardia is a heart rate greater
than 100 beats per minute that originated
from the sinus node.
• Rate: 100 to 180 beats per minute
• P Waves precede each QRS complex
• PR interval, QRS complex , Conduction is normal
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Sinus bradycardia is a heart rate less
than 60 beats per minute and originates
from the sinus node (as the term “sinus”
refers to sinoatrial node). It has the
following characteristics
19. P wave and PR interval
• The Normal P wave represents atrial depolarization. This wave is generated by an impulse from
the SA node in the right atrium and is conducted across the atria.
• In a normal EKG, the P-wave precedes the QRS complex.
• The P wave is virtually positive in leads aVL,avf,I,V4-V6. It’s negative AVR. Frequently biphasicin V1.
• Normal duration is 0.06-0.12 seconds (1.5 to 2.75 small boxes).
Abnormal P wave( P mitral,P pulmonar.)
None P wave (atrial fibrillation or flutter)
The PR Interval indicates AV conduction time, from the start of atrial depolarization to the start of
ventricular depolarization (the QRS cømplex).
Normally this interval is 0.12 to 0.20 seconds (3 to 5 small boxes) in adults, longer in elderly people.
This interval shortens with increased heart rate
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20. The QRS complex indicates ventricular depolarization.
Depolarization triggers contraction of the ventricles.
Its duration is no greater than 120 ms (three small squares).
In a right ventricular lead (Vj), the S wave is greater than
the R wave.
In a left ventricular lead (V5 or V6), the height of the R wave
is less than 25 mm.
The ST segment represents the early part of ventricular
repolarization.
Normally the ST segment is flat relative to the baseline.
An elevated ST can indicate an acute myocardial infarction
or other cardiac conditions.
• Several underlying conditions and other factors can cause
an ST segment depression(hypokalemia. Miocardial
ishemia,some medications.
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22. The T wave indicates the repolarization
of the ventricles.
In the normal ECG (see below) the T
wave is always upright in leads I, II,
V3-6, and always inverted in lead
aVR.
Inverted T wave Only III lead is normal.
The other leads are variable depending
on the direction of the QRS and the
age of the patient.
Abnormal T waves are associated
with depression or elevation of the ST
segment. It indicate myocardial
ishemia.
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23. The QT interval represents the time for ventricular activity including both
depolarization and repolarization.
It is measured from the beginning of the QRS complex to the end of the T wave.
Normally, the QT interval is 0.36 to 0.44 seconds (9-11 boxes).
QT prolongation
Certain medications can also cause QT prolongation, including some belonging to
the following groups:antibiotics.antidepressants,antiarrhythmics.
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24. ECG Best Practices
• Always protect the patient’s privacy
and dignity by draping with a sheet
to minimize exposure.
• Lead placement and patient
positioning should be the same for
subsequent ECGs on any individual
patient.
• During the procedure, record any
clinical signs (e.g. chest pain) in the
notes or on the ECG tracing itself.
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