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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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46
Lead II
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Fig. 3.25 Identify two
abnormalities
Fig. 3.26 Identify the
abnormality
Fig. 3.27 Identify the
abnormal wave
3 ECG Waveforms
Lead II
Fig. 3.28 Label the
abnormal wave
6. Label the abnormal wave in the ECG of Fig.3.29. Describe the abnormality and
name one condition in which you get this type of abnormal wave.
7. Measure the amplitude of R and S waves in the ECG of Fig.3.30.
8. Measure the amplitude of R and S waves in the ECG of Fig.3.31. Mark the U
wave by placing arrow.
Lead II
Lead II
Lead II
3.2 Genesis ofQRS Complex
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Fig. 3.29 Label the
abnormal wave
Fig. 3.30 Measure the
amplitude of R and S
waves
Fig. 3.31 Measure the
amplitude of R and S
waves and mark the
U wave
47
Lead II
Answers
1. False 2. False 3. True 4. False 5. False 6. a 7. b 8. d 9. c 10. d
Case Studies
1. The answer of this question is given in Figs.3.32, 3.33, 3.34, 3.35, 3.36 and 3.37.
2. The two abnormalities are pathologic Q waves and inversion of T wave
(Fig.3.38).
3. The abnormality in this ECG is presence of pathologic Q waves. The Q waves
and S-T segments are marked by arrows (Fig.3.39).
4. The abnormality in the ECG is inversion of T wave (Fig.3.40). It is seen in myo-
cardial ischaemia.
Lead V1
48
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3 ECG Waveforms
Fig. 3.32 Answer of Case
Study Question 1
(Fig.3.19)
Fig. 3.33 Answer of Case
Study Question 1
(Fig.3.20)
Fig. 3.34 Answer of Case
Study Question 1
(Fig.3.21)
R
P
Lead II
Lead II
R
P
S
Lead V1
T
Q
r
T
P
s
U
T
Fig. 3.35 Answer of Case
Study Question 1
(Fig.3.22)
Fig. 3.36 Answer of Case
Study Question 1
(Fig.3.23)
P
Lead aVR
r
P
S
Lead V1
T
S
T
Lead II
Lead II
3.2 Genesis ofQRS Complex
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Fig. 3.37 Answer of Case
Study Question 1
(Fig.3.24)
49
R
T
P
Fig. 3.38 Answer of Case
Study Question 2
Fig. 3.39 Answer of Case
Study Question 3
Fig. 3.40 Answer of Case
Study Question 4
Lead II
S-T
q
Q
S
T
Q
S-T
Q
Lead II
T
Inverted T wave
T
50
Tall T wave
R
Lead II
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3 ECG Waveforms
5. The abnormality in the ECG is tall T waves. The J points are marked with arrows
(Fig.3.41).
6. The abnormal wave is marked by arrow (Fig.3.42). This is a symmetrical, deep
and pointed T wave inversion. This is seen in myocardial infarction.
7. To calculate the amplitude of R and S waves, P-R segment is used as isoelectric
line. The horizontal blue line represents the P-R segment, which is prolonged
over the isoelectric S-T segment for calculation of amplitude of waves (Fig.3.43).
The amplitude of r wave is 4×0.1mV=0.40mV.Similarly, the amplitude of
S wave is 5×0.1mV=0.50mV.
8. The amplitude of R wave is 6×0.1s=0.6mV (Fig.3.44). The amplitude of S
wave is 23×0.1mV=2.3mV.The U wave is marked by arrow.
Fig. 3.41 Answer of Case
Study Question 5
Fig. 3.42 Answer of Case
Study Question 6
Fig. 3.43 Answer of Case
Study Question 7
Lead II
T
J
Lead IILead II
Inverted T wave
r
T
J
s
Fig. 3.44 Answer of Case
Study Question 8
U
S
Lead V1
Chapter 4
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ECG Intervals andSegment
Learning Objectives
After studying this chapter, the reader will learn about:
• P-R interval
• P-R segment
• P-P interval
• R-R interval
• QRS interval
• S-T segment
• Q-T interval
• T-Q segment
• Ventricular activation time
Various time intervals and segments are studied while reading an ECG.A segment
in ECG is the area between two waves. Segment is usually isoelectric in normal
ECG. Elevation or depression and lengthening or shortening of segments are of
great signicance while studying segments. An interval in ECG is a time duration
that includes one segment and one or more waves. While studying intervals morphology or depression or elevation is not considered. The important intervals and
segments are the following:
• P-R interval
• P-R segment
• P-P interval
• R-R interval
• QRS interval
• S-T segment
• Q-T interval
Ltd. 2024
T. K. Koley, Rapid Review of ECG,
https://doi.org/10.1007/978-981-99-9116-7_4
51© The Author(s), under exclusive license to Springer Nature Singapore Pte
52
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4 ECG Intervals andSegment
4.1 P-R Interval
In a QRS complex, P-R interval is the time interval between the beginning of P
wave to beginning of Q wave or R wave (in absence of Q wave) (Fig.4.1). It denotes
the time interval between atrial and ventricular depolarization and is mainly contributed by AV nodal delay in conduction of the impulse.
It includes the time for atrial depolarization, normal conduction delay of the AV
node (0.07s) and time for the passage of impulse through bundle of His and bundle
branches to the onset of ventricular depolarization.
The normal P-R interval is 0.12–0.20s. Prolonged P-R interval is seen in the rst
degree heart block and shortened P-R interval is seen in Wolff–Parkinson–White
syndrome and Lown–Ganong–Levine syndrome.
Fig. 4.1 P-R interval. In
this ECG the number of
small boxes between
beginning of P wave and
beginning of R wave is 5
(as shown with arrow).
Hence, P-R interval is
5×0.04s=0.20s
P-R segment
4.2 P-R Segment
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Tips and Tricks
• Often mild P-R interval prolongation is found in athletes and normal persons. No
treatment is required.
• Normal P-R interval is 3–5 small squares in horizontal axis in ECG.
53
4.2 P-R Segment
P-R segment starts from the end of the P wave to the beginning of the QRS complex
(Fig.4.2). It is an isoelectric line. It does not include the P wave and is part of the
P-R interval. It allows time for the atria to empty blood into the ventricles before
ventricular contraction begins. It represents the time taken by electrical impulse to
travel through the AV node, bundle of His, bundle branches and Purkinje system.
P-R segment is frequently used as isoelectric baseline for calculating the amplitude
of the waves of ECG.
Fig. 4.2 P-R segment
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4 ECG Intervals andSegment
4.3 P-P Interval
P-P interval is the time interval between two consecutive P waves. It is calculated
from the beginning of any P wave to the beginning of the subsequent P wave. It
helps in calculation of atrial rate. In normal sinus rhythm, P-P interval is equal to the
R-R interval. Varying P-P interval is seen in sinus arrhythmia.
4.4 R-R Interval
R-R interval is the time interval between two consecutive R waves (Fig.4.3). It
helps in calculation of ventricular rate (heart rate). Slight variation of R-R interval
may be normal due to effect of respiration.
Fig. 4.3 R-R interval. In this ECG, there are 21 small boxes between the peak of one R wave to
the peak of next R wave (as shown with arrow). Hence, the R-R interval is 21×0.04s=0.84s
4.5 QRS Interval
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55
4.5 QRS Interval
QRS interval or duration denotes the total time taken for ventricular depolarization.
It is calculated from beginning of Q wave to end of S wave or J point (junction
point—it is junction between end of S wave and beginning of S-T segment, Figs.4.4
and 4.5). The normal QRS interval is less than 0.12s. It is prolonged in various
conditions enumerated in Box 4.1.
Box 4.1 Causes of Wide QRS Complex
Bundle branch block
WPW syndrome
Intraventricular conduction delay
Idioventricular rhythm
Hyperkalaemia
Ventricular premature beat
Ventricular tachycardia
Fig. 4.4 QRS interval.
There are two small boxes
between the beginning of
R wave to the end of S
wave. Hence, the QRS
duration is
0.04s×2=0.08s
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