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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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192
25 mm/s. 10 mm = 1mV
25 mm/s. 10 mm = 1mV
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14 Bundle Branch Block
Case Studies
1. A 35-year-old gentleman was undergoing medical check-up for recruitment in
army. His ECG (Fig. 14.15) is given below. Identify the conduction
disturbance.
2. A 65-year-old gentleman came for medical check-up. He has history of hyper-
tension. Examine the 12-lead ECG (Fig.14.16) given below. Identify the abnormality. Give two important points in favour of your diagnosis.
IIIIII aVRaVL aVF
V1 V2 V3 V4 V5 V6
Fig. 14.15 Identify the conduction disturbance
III
V1 V2
Fig. 14.16 Identify the ECG abnormality
IIIaVR aVL aVF
V3 V4 V5 V6
14.2 Left Bundle Branch Block
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193
Answers
1. True 2. True 3. True 4. True 5. False 6. a 7. b 8. d 9. d 10. d
Case Studies
1. The conduction abnormality is RBBB.
• There is rsR’ complex in lead V1.
• Duration of QRS complex in lead V1 is 0.14s and there are S-T segment and
T wave changes in lead V1.
• Note the wide s wave in lead V6.
RBBB is frequently seen in normal healthy persons and no active intervention is
required.
2. The conduction abnormality is LBBB.The two most important points in favour
of the diagnosis are wide QRS complex in lead V6 (more than 0.12s) with S-T,
T changes and presence of notch in QRS complexes of lead V5 and lead V6,
which signify RsR’ complexes. Also note the absence of q waves in these leads.
QRS axis is deviated to left.
LBBB in older age group may serve as an important marker for cardiovascular disease or death. This patient should be properly investigated and treated. If
coexisting heart failure is detected, he may need cardiac resynchronization therapy. In asymptomatic individuals, no further therapy is needed but regular follow- up is essential.
Chapter 15
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Fascicular Block
Learning Objectives
After studying this chapter, the reader will learn about:
• Left anterior fascicular block
• Left posterior fascicular block
• Bilateral bundle branch block
• Trifascicular block
15.1 Fascicular (Divisional) Blocks
The left bundle branch divides into two fascicles: anterior and posterior fascicles.
When one of the fascicles is blocked, the impulse is conducted through the other
fascicle. Since the conduction is very rapid through the fascicles, the fascicular
block does not prolong the QRS duration.
15.1.1 Left Anterior Fascicular Block
Left anterior fascicular block also called left anterior hemiblock (LAHB) is more
common than the block of the posterior fascicle. The anterior fascicle is supplied by
a single artery and it is long and thin, whereas the posterior fascicle has dual blood
supply and it is short and thick. The impulse passes via the posterior fascicle of the
left bundle and then anterior fascicle is activated by the Purkinje bres distal to the
site of the block. The various causes of LAHB are enumerated in Box 15.1. The
ECG manifestations of LAHB are the following:
Ltd. 2024
T. K. Koley, Rapid Review of ECG,
https://doi.org/10.1007/978-981-99-9116-7_15
195© The Author(s), under exclusive license to Springer Nature Singapore Pte
196
V2
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15 Fascicular Block
Box 15.1 Causes of LAHB
Coronary artery disease
Left ventricular hypertrophy
Hypertension
Cardiomyopathy
Aortic stenosis
• Left axis deviation of QRS axis. The QRS axis lies between −30° and −90°.
• There are deep S waves in lead II and III and the depth of S wave in lead III is
more than the depth of S wave in lead II (Fig.15.1).
• The QRS duration is not prolonged (less than 0.12s).
• In lead I, there is a tall R wave after the prominent q wave.
• The normal q wave in lead I and a VL becomes prominent.
• Prominent initial r waves in lead II, III and aVF.
I
25 mm/s. 10 mm = 1 mV
V1
Fig. 15.1 Anterior wall myocardial infarction with left anterior hemiblock
II
III
V3
aVR
V4
aVL
V5
aVF
V6
15.1 Fascicular (Divisional) Blocks
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• The normally present small q waves tend to disappear in leads V5 and V6.
• In lead V5 and lead V6, the R wave height tends to diminish.
• In lead V5 and lead V6, the S wave becomes prominent and there may be terminal slurring.
Tips and Tricks
• If you come across an ECG showing left axis deviation, think of possibility
of LAHB.
• Next check the depths of S waves in leads II and III to further conrm the diagnosis. The depth of S wave in lead III is more than the depth of S wave in
lead II.
197
15.1.2 Left Posterior Fascicular Block
Left posterior fascicular block also called left posterior hemiblock (LPHB) is due
to the lesion in the posterior fascicle of the left bundle. Here the impulse is blocked
at the left fascicle, and hence, the impulse travels via the anterior fascicle and then
via the interconnected Purkinje bres, the impulse travels via the posterior fascicle
distal to the block. It is not very common. The ECG manifestations are the
following:
• The QRS axis is deviated to right (beyond 120°).
• There are prominent R waves in leads II, III and aVF, and the R wave in lead III
is the tallest among them (Fig.15.2).
• In lead l and aVL, there are prominent S waves.
• There is a small but prominent q wave in lead II, III and aVF.
• In lead I, there is a small but prominent r wave.
• The T wave may be inverted in lead II, III and aVF.
Tips and Tricks
• It is important to rule out possibility of right ventricular hypertrophy and myocardial infarction before making a diagnosis of left posterior hemiblock.
• Look for right axis deviation and the height of R waves in leads II, III and aVF
and the R wave in lead III is the tallest among them.
198
V1 V2
V5
V6
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15 Fascicular Block
III III aVRaVL
25 mm/s. 10 mm = 1 mV
V3
Fig. 15.2 Left posterior fascicular block. It is always important to rule out right ventricular hypertrophy. This patient had come with chest pain and the chest leads show features of anterior wall
myocardial infarction
V4
aVF
15.1.3 Bilateral Bundle Branch Block
Bilateral bundle branch block also called bifascicular block means block in conduction in both the right and the left bundle. The different types of bilateral bundle
branch block are the following:
• RBBB with LAHB: Chest leads show RBBB pattern and left axis deviation in
standard leads (Fig. 15.3). It is a common type of bifascicular block, often
observed in myocardial infarction.
• RBBB with LPHB: There is RBBB with right axis deviation. It is a very rare
combination, and the initial 0.08s determines the axis and the divisional block.
Trifascicular block is a combination of RBBB with either LAHB or LPHB with rst
degree AV block (prolonged P-R interval).
25 mm/s. 10 mm = 1 mV
15.1 Fascicular (Divisional) Blocks
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III III aVRaVL aVF
199
V1
Fig. 15.3 Right bundle branch block with left anterior hemiblock. Note the broad QRS complex
in lead V1 with S-T segment, T wave change. There are also deep S waves in leads II and III and
the depth of S wave in lead III is more than that of lead II.Hence, this is a bifascicular block
V6V5V4V3V2
Self-Assessment Questions
1. In LAHB, the QRS axis is normal. True or false?
2. In LPHB, R waves are recorded in lead II and lead III.True or false?
3. The presence of LAHB in an ECG can cause left axis deviation. True or false?
4. LPHB is characterized by a delay in the conduction of the left anterior fascicle
of the bundle branches. True or false?
5. Bifascicular block is characterized by the presence of conduction block in both
right and left bundle simultaneously. True or false?
6. Which ECG nding is commonly associated with LAHB?
a. Right axis deviation b. Left axis deviation c. Prolonged P-R interval d.
Shortened Q-T interval
7. Which ECG nding is commonly associated with LPHB?
a. Right axis deviation b. Left axis deviation c. Prolonged P-R interval d.
Tall R waves in leads V1 and V2
8. The combination of LAHB and RBBB is known as:
a. LPHB b. Bifascicular block c. LBBB d. Anterior fascicular block
9. Which ECG nding is characteristic of bifascicular block?
a. Prolonged Q-T interval b. CHB c. Wide QRS complex d. Delta wave
10. Which ECG nding is commonly associated with bifascicular block and
may indicate an increased risk of progression to complete heart block?
a. Q-T interval shortening b. S-T segment depression c. Prolonged P-R
interval d. T wave inversion
200
25 mm/s. 10 mm = 1 mV
V4
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15 Fascicular Block
Case Studies
1. A 60-year-old gentleman came for routine evaluation. He has past history of
hypertension, diabetes and dyslipidaemia. He is asymptomatic. Examine the
12-lead ECG (Fig.15.4) given below. Identify the abnormality. Give two important points in favour of your diagnosis.
2. A 50-year-old gentleman came for medical check-up. He has past history of
hypertension for 25years. He has taken irregular treatment for hypertension. He
was asymptomatic. On examination, his blood pressure was 170/90 mmHg,
pulse rate was 88/min, heart sounds were normal and chest was clear. His ECG
is given in Fig.15.5. What is your diagnosis?
IIIIII aVRaVL aVF
V6V5V4V3 V2 V1
Fig. 15.4 Identify the ECG abnormality
III
25 mm/s. 10 mm = 1 mV
V1 V2
Fig. 15.5 Identify the ECG abnormality
III
V3
aVR
aVL
V5
aVF
V6
15.1 Fascicular (Divisional) Blocks
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201
Answers
1. False 2. True 3. True 4. False 5. True 6. b. 7. a. 8. b. 9. c. 10. c.
Case Studies
1. The conduction abnormality is RBBB with LAHB.This is a bifascicular block.
There is wide QRS complex in lead V1 with S-T, T changes with slurred s waves
in leads V5 and V6. These are diagnostic of RBBB.LAHB is diagnosed by presence of S waves in lead II and lead III.The depth of S wave in lead III is more
than the depth of S wave in lead II.Besides this if we consider lead I and lead
aVF, there is left axis deviation.
Asymptomatic bifascicular block usually does not require any treatment.
condition. Any provoking medication should be withdrawn. However, he should
be advised regular cardiac check-up.
2. The ECG shows left axis deviation. There are prominent S waves in lead II and
lead III.The depth of S wave in lead III is more than the depth of S wave in lead
II.The QRS duration is normal. Hence, the diagnosis is LAHB.
Patients of LAHB are at higher risk of cardiovascular morbidity and mortality. In this patient most likely it is due to long standing uncontrolled hypertension. Hypertension should be treated with appropriate antihypertensive. He
should also be advised regular follow-up.
Part IV
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Coronary Artery Disease
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