Transcript Basics in ECG Interpretation (Part 1) – By Dr. Anidu Pathirana

Basics in Electro Cardio Gram
Interpretation – Part 1
Dr Anidu Pathirana
MBBS(Col), MD(Col.), MRCP(UK), FCCP
What is Electro Cardio Gram ?
 Tracing of heart’s electrical activity
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Electrical activity of cells
Resting membrane potential – 70 mV
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Electrical activity of cells
Depolarization
Action potential
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EXCITABILITY
Electrical activity of Nerve & Muscle
SELF- PROPAGATION
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Electrical & Mechanical activity of heart
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Automaticity
Rhythmicity
Conductivity
Excitability
Contractility
 Organizational
hierarchy
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Electro Mechanical Disssociation
 Look at the patient first,
 Look at the ECG afterwards
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Recording of an ECG:
History
 Pick up electrical activity
(depolarization wave) from
outside.
 By placing 2 electrodes on
patient either side of the
heart
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Recording of an ECG:
Contact electrodes n=10
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How does the ECG works ?
 Electrodes are paired (one positive and other negative)to
sense the change in voltage between them. Such a pair is
called lead.
12- lead ECG
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Leads look at the heart in two planes & from
different directions
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Recording vectors
 Electrical impulse travels towards positive gives a positive
deflection
 Electrical impulse travels away from positive electrode
gives a negative deflection 13
ECG recording paper
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Recorded ECG
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Recording of an ECG
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Normal ECG complex
 P wave- atrial depolarization
 QRS together in a complex ventricular depolarization
 T wave- ventricular
repolarization
 U wave- inter ventricular
septum repolarization
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Normal ECG complex
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Durations & Intervals
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Normal intervals
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Systematic reading
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Check the details: identification, date & time
Calibration
Rhythm: Normal Sinus Rhythm or not
Rate
Cardiac axis
P-wave, PR-interval, QRS complex, ST segment,
QT- interval, T & U – wave
 Other signs- Ischemia, infraction, hypertrophy
 Compare with previous ECGs
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Calibration
Calibration
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Paper speed
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Rhythm: Normal sinus rhythm or Not
 Every P wave is followed by QRS, every QRS preceded by
P; Rate anywhere between 60-99; PR interval 3-5 squares;
always upright in lead I & II
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How to recognize an arrhythmia?
1. Is there any electrical activity?
2. Are there any recognizable complexes?
3. What is the ventricular (QRS) rate?
4. Is the QRS rhythm regular or irregular?
5. Is the QRS complex width normal or prolonged?
6. Is atrial activity present?
7. How is atrial activity related to ventricular activity?
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How to recognize an arrhythmia?
2. Are there any recognizable complexes?
3. What is the ventricular (QRS) rate?
4. Is the QRS rhythm regular or irregular?
5. Is the QRS complex width normal or prolonged?
6. Is atrial activity present?
7. How is atrial activity related to ventricular activity?
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Rhythm recognition:
Q1-Is there any electric activity?
 No – Check leads, electric connection
 No – Check gain
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Rhythm recognition:
Q1-Is there any electric activity?
No- Asystole
Yes- but only P waves called P wave asystole
Yes- Go to Q2
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How to recognize an arrhythmia?
1. Is there any electrical activity?
3. What is the ventricular (QRS) rate?
4. Is the QRS rhythm regular or irregular?
5. Is the QRS complex width normal or prolonged?
6. Is atrial activity present?
7. How is atrial activity related to ventricular activity?
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Rhythm recognition:
Q2-Are there any recognizable complexes?
 No- most likely ventricular fibrillation
 Yes- Q3
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How to recognize an arrhythmia?
1. Is there any electrical activity?
2. Are there any recognizable complexes?
4. Is the QRS rhythm regular or irregular?
5. Is the QRS complex width normal or prolonged?
6. Is atrial activity present?
7. How is atrial activity related to ventricular activity?
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Rhythm recognition:
Q3- What is the ventricular rate?
 Look at lead II, rhythm strip. Determine distance between
one RR interval. Use one of the formula,
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Rate Calculation: An example
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Rate Calculation: In an irregular rhythm
 Count number of beats in a 6 sec strip and multiply by 10
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Classification of Arrhythmia
Brady arrhythmia
 Rate <60/min.
Tachy arrhythmia
 Rate > 100/min.
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How to recognize an arrhythmia?
1. Is there any electrical activity?
2. Are there any recognizable complexes?
3. What is the ventricular (QRS) rate?
5. Is the QRS complex width normal or prolonged?
6. Is atrial activity present?
7. How is atrial activity related to ventricular activity?
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Rhythm recognition:
Q4- Is the rhythm regular or irregular?
 Look at lead II. Use a paper strip to map out consecutive
beats. Measure RR interval for ventricular rhythm & PP
interval for atrial rhythm
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Rhythm recognition:
Q4- Is the rhythm regular or irregular?
 If regular : Go to Q5
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Rhythm recognition:
Q4- Is the rhythm regular or irregular?
 If irregular- Decide if occasionally irregular or totally
irregular or irregular in a cyclical pattern
 Irregularly irregular rhythm
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Rhythm recognition:
Q4- Is the rhythm regular or irregular?
 Regularly irregular
Sinus arrhythmia
P wave morphology & axis normal, PP interval >0.16 sec or 10%
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Sinus Pause
 In case SA node fails- if failure is brief and recovery is
prompt result is only a missed beat.
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Atrial Escape
 If recovery is delayed and some other focus assumes
pacing function resulting in an escape beat or escape
rhythm.
 Other atrial foci act as a pacemaker, rate = 60-80bpm,
P waves have abnormal axis and looks different but QRS
complex appears exactly the same
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Junctional Escape
 AV node as a pacemaker, rate 40-60bpm,P waves are
inverted, appear before after or hidden within QRS,
QRS is normal
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Ventricular Escape
 Ventricular myocardium as pacemaker, depolarization
wave spreads slowly via myocardium and not via His
bundle or its branches
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Atrial Premature Beat
 Sometimes an irritable focus could dominate over SA node
 An irritable focus in one of the atria. ABP has a different
looking P wave while QRS complex appears normal
 If non conducted would deform the preceding T wave
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Junctional Premature Beat
 An irritable focus at AV junction, P wave is usually inside
QRS and not visible. If visible, it is negative in lead II and
positive in aVR
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Premature Ventricular Complexes
 Common. Heartbeat is initiated at ventricle. No P waves.
May produce bizarre looking T wave
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How to recognize an arrhythmia?
1. Is there any electrical activity?
2. Are there any recognizable complexes?
3. What is the ventricular (QRS) rate?
4. Is the QRS rhythm regular or irregular?
6. Is atrial activity present?
7. How is atrial activity related to ventricular activity?
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Rhythm recognition:
Q5-Is QRS complex width normal or prolonged?
 QRS width normal <0.12 sec / 3 small squares
 Narrow Complex (Originate above the bifurcation of
bundle of His)
 QRS wider than 0.12 sec / 3 small squares
 Broad Complex(ventricular or supra ventricular with
aberrant conduction)
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Rhythm recognition:
Q5-Is QRS complex width normal or prolonged?
 Narrow complex regular tachycardia
 Broad complex regular tachycardia
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 >3 consecutive wide QRS, capture and fusion beats
How to recognize an arrhythmia?
1. Is there any electrical activity?
2. Are there any recognizable complexes?
3. What is the ventricular (QRS) rate?
4. Is the QRS rhythm regular or irregular?
5. Is the QRS complex width normal or prolonged?
7. How is atrial activity related to ventricular activity?
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Rhythm recognition:
Q6- Is atrial activity present?
 Yes : Normal P-wave ( axis +15 to +75)
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Rhythm recognition:
Q6- Is atrial activity present?
 Yes : Abnormal P-wave
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