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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_2818_Библиотеки_им_академика_М_И_Перельмана
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10.2 Normal ECG Variants
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Another normal ECG is shown in Fig.10.2. The QRS axis is normal. All the
complexes in lead aVR are inverted. P-R interval and QRS duration are normal. The
transition zone is located in lead V3. rS complex is recorded in lead V1, and Rs
complex is recorded in lead V6. All the complexes in respective leads are normal in
conguration.
Tips and Tricks
• Never look at the computerized interpretation of ECG.
• If any doubt, repeat the ECG after a few minutes.
10.2 Normal ECG Variants
Variants of normal ECG can be dened as ECG readings which seem abnormal but
are found in ordinary healthy people. ECG readings are based on a range of factors
including age, sex, body mass index, heart position, race, food consumption and
exercise. It is easy to recognize some of the normal variants that have been identied and given names such as persisting juvenile pattern, early repolarization syndrome. It is important to recognize the normal variants to avoid confusion with
cardiac anomalies. However, the ECG should always be interpreted in context of the
clinical features of the patient. Some of the important normal variants are enumerated in Box 10.1.
I
II
III
II
Fig. 10.2 Normal ECG from a 35-year-old gentleman
aVR V1 V4
aVL
aVF
V5V2
V3 V6
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Box 10.1 Normal ECG Variants
Variations of P wave: Notching or peaking of P waves with normal duration.
A short P-R interval may be normal in young adults or healthy children.
Variation of Q wave: Prominent Q waves of normal duration may appear in
normal persons depending upon the heart position and body built.
Variation of T waves: Abnormally tall T waves may appear without any other
abnormality. Besides this non-specic T wave inversion is also common in
normal healthy people.
Variation of QRS complex: High amplitude of R and S waves may appear in
precordial leads in thin persons. Low amplitude of R and S waves may be
seen in obese persons.
Abnormal looking Q wave and T wave inversion in lead III which disappear
on taking a deep breath. The T wave becomes upright.
Non-specic widening of QRS complex, which does not full the criteria of
any bundle branch block pattern. Incomplete right bundle branch block is
commonly seen in young people.
S-T segment may be elevated by 1mm or more in lead V2 and less in lead V3.
Early repolarization syndrome.
Persistent juvenile pattern.
10 Normal ECG andIts Variants
10.2.1 Well-Recognized Variants ofNormal ECG
10.2.1.1 Early Repolarization Syndrome
Early repolarization syndrome is a common variant and is often confused with myocardial infarction and pericarditis. The main ECG feature is elevation of J point and
S-T segment. The J point elevation often creates a distinct notch or hook in the distal
or descending limb of the QRS complex, called J wave.
The S-T segment elevation is usually about 2–3mm but may be up to 5mm in
some cases. The S-T segment is concave upwards (in contrast to myocardial infarction) and it is more prominent in leads V4–V6 (Fig.10.3). Serial ECG recordings,
however, do not show any evolutionary changes, as observed in myocardial infarction. The S-T segment elevation frequently returns to baseline with exercise. The
ECG manifestations are the following:
• Concave upwards S-T segment elevation
• J point elevation
• Prominent J waves
• Tall R waves in leads V4–V6
• Tall and symmetrical T waves
• Narrow q waves in leads V4–V6
• Sinus bradycardia
V1 V2
V3
V4
V5
V6
10.2 Normal ECG Variants
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I III
10 mm = 1 mV. 25 mm/s.
II
aVR
J wave
aVL
aVF
J wave
Fig. 10.3 Early repolarization syndrome. This ECG is taken from a 30-year-old gentleman who
presented with chest pain. Note the concave upwards S-T segment elevation in leads V4, V5 and
V6. Note also the prominent J waves in leads V4 and V5. This type of ECG is often confused with
S-T segment elevation of myocardial infarction
10.2.1.2 Persistent Juvenile Pattern
The T wave is normally inverted in leads V1–V4in infancy and childhood, and if
these changes persist in adulthood, it is known as persistent juvenile pattern
(Fig.10.4). It is more common in females and is frequently associated with other
normal variants. The main ECG feature is T wave inversion which is not symmetric
or deep. It should be differentiated from other conditions, which may produce T
wave inversion in chest leads, including anterior wall myocardial ischaemia, myocarditis and pulmonary embolism.
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10 Normal ECG andIts Variants
I
V1
Fig. 10.4 Persistent juvenile pattern. Note the inversion of T waves in lead V1 to lead V3. Rest of
the ECG is normal
II
V2
III
V3
aVR
V4
aVL
V5
aVF
V6
10.2.1.3 Non-specic T Wave Changes
Often we come across normal persons in whom the T waves are inverted, and
detailed examination and investigation do not reveal any anatomical or pathological
changes in the heart. T waves may be inverted in athletes in leads V4–V6. The T
waves may be inverted in the following conditions also:
• After hyperventilation
• Anxiety and fear
• After heavy meal
Tips and Tricks
• The ECG of early repolarization syndrome, persistent juvenile pattern and nonspecic T wave changes is often confused with myocardial infarction due to S-T
segment elevation and T wave changes.
• You may repeat the ECG after deep inspiration if there is T wave inversion.
• If there is confusion, repeat the ECG and look for any serial change.
• In myocardial infarction, the ECG ndings change with time, whereas in early
repolarisation syndrome, the ECG ndings are xed.
• If doubt persists, take help of other investigations like Trop I estimation and
echocardiography.
10.3 Method ofInterpretation ofECG
The interpretation of ECG starts with the history and clinical examination of the
patient. This is often the most neglected step. ECG should always be interpreted in
light of the clinical ndings. This gives us the clue based on which it becomes easier
to read ECG.This step is very important for the beginners, as it enhances the accuracy of interpretation of ECG.Clinical diagnosis and ECG are complimentary to
each other. The study of an ECG should be systematic; otherwise, important ndings will be missed and the diagnosis will become difcult. The following points
should be considered while studying an ECG to arrive at a diagnosis:
10.3 Method ofInterpretation ofECG
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10.3.1 Rate
The rate should be calculated to rule out bradycardia or tachycardia.
10.3.2 Rhythm
The rhythm should be checked in the beginning. It is important to observe if the
rhythm is regular or irregular. If regular, it should be checked whether the complexes are originating from SA node (sinus rhythm) or from any supraventricular or
ventricular focus. If irregular, it is important to rule out sinus arrhythmia in the
beginning, i.e. before considering any supraventricular or ventricular arrhythmia.
The relation between P wave and QRS complex should be noted. If there are abnormalities, then they should be written down and correlated with the clinical ndings.
In normal ECG, every P wave should be followed by a QRS complex. Rhythm
should always be examined in lead II or lead V1in a rhythm strip.
10.3.3 P-R Interval
The P-R interval should be checked in the leads where the P waves are seen very
clearly, e.g. lead II.Prolongation of P-R interval indicates rst-degree heart block.
Short P-R interval with delta wave indicates WPW syndrome.
10.3.4 P Waves
It is important to rule out any right or left atrial enlargement by examination of P
waves in all the 12 leads but especially in lead II and lead V1. The P wave is always
inverted in lead aVR and it may be biphasic in lead V1. If P wave is upright in lead
aVR, then there may be dextrocardia. Inverted P waves in leads II, III and aVF indicate nodal/junctional rhythm.
10.3.5 QRS Complexes
The QRS complexes should be studied in all the 12 leads and it should be checked
if they are of normal conguration and correspond to the normal complexes in all
the 12 leads. The following points should be studied in the QRS complexes:
(a) Duration
(b) VAT
(c) Presence of normal or pathological Q waves
(d) Amplitude of R and S waves
(e) QRS axis: To rule out left or right axis deviation
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10 Normal ECG andIts Variants
10.3.6 T Waves
It should be checked whether the T waves are upright or inverted. The T wave is
normally inverted in lead aVR.Deep and symmetric T wave inversion is a sign of
myocardial ischaemia. Asymmetric inversion is a feature of strain pattern associated
with left or right ventricular hypertrophy.
10.3.7 U Waves
It should be checked whether the U waves are present or absent. If present, they may
be normal or may be a feature of hypokalaemia.
10.3.8 S-T Segment
S-T segment should be carefully examined to rule out any elevation or depression.
S-T segment elevation indicates myocardial infarction or pericarditis or ventricular
aneurysm. S-T segment depression indicates myocardial ischaemia. S-T segment
depression with a reverse check sign or scooped S-T segment depression is a feature
of digitalis effect.
10.3.9 Left or Right Ventricular Hypertrophy
The presence of left or right ventricular hypertrophy should be checked. For LVH one
must look for the sum of amplitude of S wave in lead V1 and amplitude of R wave in
lead V5 or lead V6. If it is more than 35mm, then one should look for rest of the features as described in Chapter 12. For RVH, one should look for the R:S ratio in lead
V1. If it is more than 1, then one must look for the other features of RVH. You will read
in details about ECG features of right and left ventricular hypertrophy in Chapter 12.
10.3.10 Conduction Disturbance
Conduction disturbances like rst, second and third degree heart block should be
checked. Left or right bundle branch block should be excluded. If rSR’ pattern is
seen in lead V1, then look for other features of RBBB and if rSR’ pattern is seen in
lead V6, then look for other features of LBBB. You will read in details about conduction disturbances in Chapter 13.
10.3 Method ofInterpretation ofECG
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Reporting of ECG
ECG reporting should be done in details and the diagnosis should be mentioned
clearly. ECG should be reported in the following format.
Name:________ Age:__________ Sex:_____ Drugs: ___________
Date & Time: ________
Rate: _________ Rhythm: _______ P wave: _______ P-R interval: _______
Q-T interval: _________
QRS complex:
a) Conguration________________
b) Duration____________________
c) QRS axis___________________
d) VAT_______________________
S-T segment:__________________
T wave: _______________
U wave: ________________
Diagnosis: _______________
Tips and Tricks
• It is always preferable to look at any previous ECG for comparison before reporting an ECG.
Self-Assessment Questions
1. J point is elevated in early repolarization syndrome. True or false?
2. Biphasic P wave is seen in normal persons not suffering from any cardiac dis-
ease. True or false?
3. In early repolarization syndrome, there is S-T segment depression in leads V4–
V6. True or false?
4. In young people, T wave inversion is often seen normally in leads V1–V3. True
or false?
5. T wave inversion in lead III only indicates inferior wall ischaemia? True
or false?
6. The normal rhythm in ECG is:
a. Sinus rhythm b. Atrial brillation c. Ventricular brillation d. Asystole
7. The normal upper limit of the P-R interval in ECG is:
a. 0.10s b. 0.20s c. 0.30s d. 0.40s
8. Prolonged Q-T interval is seen in:
a. Hypocalcaemia b. Hyponatraemia c. Hypercalcaemia d. Hypernatraemia
9. The normal S-T segment is:
a. Isoelectric b. Elevated with concavity upwards c. Depressed below the
isoelectric line d. Elevated with convexity upwards
10. Wide QRS complex is seen in:
a. Left bundle branch block b. Inferior wall MI c. Pericarditis d.
Atrial utter
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10 Normal ECG andIts Variants
11. P wave is always inverted in lead:
a. aVL b. aVR c. aVF d. V1
12. U wave is usually in the same direction as that of:
a. S wave b. S-T segment c. Tp wave d. T wave
13. Hyperventilation can lead to inversion of:
a. P wave b. R wave c. R’ wave d) T wave
14. The normal upper limit of QRS interval is:
a. 0.10s b. 0.12s c. 0.15s d. 0.20s
15. The QRS axis in ECG with R waves in Leads I, II and III with the tallest R
wave in lead II is:
a. Left axis deviation b. Right axis deviation c. Northwest axis d.
Normal axis
Case Studies
1. A 32-year-old gentleman had an electrocardiogram as part of a medical check-
up. Examine his 12-lead ECG given in Fig. 10.5 and answer the following
questions:
a. What is the heart rate?
b. Calculate the P-R interval.
c. Calculate the QRS duration.
d. Is normal sinus rhythm present?
e. What is your nal interpretation?
I
V1
Fig. 10.5 Calculate the P-R interval and QRS duration and interpret it
V2
II
III
V3
aVR aVL
V4
V5
aVF
V6
10.3 Method ofInterpretation ofECG
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2. A 28-year-old gentleman got his ECG done during renewal of medical insurance
policy. He has no chest pain, palpitation or dyspnoea. He does not smoke or
drink alcohol. He is not suffering from hypertension or diabetes. His lipid prole
is normal. Examine his 12-lead ECG given in Fig.10.6 and answer the following
questions.
a. Calculate the P-R interval.
b. Calculate the QRS duration.
c. Is normal sinus rhythm present?
d. What is the shape of the S-T segment?
e. Can you identify any special wave in leads V3 and V4.
f. What is your nal interpretation?
IaVR
II
III
Fig. 10.6 Calculate the P-R interval and QRS duration and interpret it
aVL
aVF
V1
V2
V3
V4
V5
V6
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10 Normal ECG andIts Variants
3. 12-lead ECG of a 25-year-old lady is given in Fig.10.7. Examine it carefully and
answer the following questions.
a. Calculate the P-R interval.
b. Calculate the QRS duration.
c. Is normal sinus rhythm present?
d. Identify the transition zone.
e. What is your nal interpretation?
IV1
II
IIIaVF
aVR
aVL
V2
V3
V4
V5
V6
Fig. 10.7 Calculate the P-R interval and QRS duration and interpret it
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