3. common cardiac arrythemias

Common cardiac
arrhythmias
1
samueldebassu@gmail.com

Objectives
 Define What is normal cardiac rhythm?
 How we define cardiac arrhythmia?
 What are the mechanisms of arrhythmia?
 Describe Types of arrhythmia?
 Describe abnormal cardiac rhythm with
ECG?
samueldebassu@gmail.com 2

Introduction
Normal cardiac rhythm
HR 60-100bpm
Origen from SA node
Cardiac impulse should propagate through
normal pathway with normal velocity

Mechanism of cardiac arrhythmia
Increase automaticity
Trigger automaticity
Re entry(circus movement)

Arrhythmogenic factors
Mnemonic HIS DEBS
 H—Hypoxia:
 I—Ischemia and Irritability:
 S—Sympathetic Stimulation:
 D—Drugs:
 E—Electrolyte Disturbances:
 B—Bradycardia:
 S—Stretch:

Common cardiac arrhythmias
Sinus Rhythms
Premature Beats
Supraventricular Arrhythmias
Ventricular Arrhythmias
AV Junctional Blocks
6

Sinus Bradycardia
• Deviation from NSR
- Rate< 60 bpm
 SA node is depolarizing slower than normal,
impulse is conducted normally (i.e. normal PR
and QRS interval).
 Can be normal in well-conditioned athletes
7

Cont.…sinuous bradycardia
8
35 bpm
• Rate?
• Regularity? regular
normal
0.08 s
• P waves?
• PR interval? 0.12 s
• QRS duration?
Interpretation? Sinus Bradycardia

Sinus Tachycardia
- Rate> 100 bpm
• SA node is depolarizing faster than normal,
impulse is conducted normally.
• Remember: sinus tachycardia is a response to
physical or psychological stress, not a primary
arrhythmia.
9

Cont.…sinuous tachycardia
10
136 bpm
• Rate?
normal
0.08 sec
• P waves?
• PR interval? 0.16 sec
• QRS duration?
Interpretation? Sinus Tachycardia

Sinus Rhythms
Premature Beats
11

a. Premature Atrial Contractions
Deviation from NSR
– These ectopic beats originate in the atria (but not in the SA
node), therefore the contour of the P wave, the PR interval, and
the timing are different than a normally generated pulse from the
SA node.
– Etiology: Excitation of an atrial cell forms an impulse that is
then conducted normally through the AV node and ventricles.
12

PAC cont.….
13
70 bpm
• Rate?
• Regularity? occasionally irreg.
2/7 different contour
0.08 s
• P waves?
• PR interval? 0.14 s (except 2/7)
• QRS duration?
Interpretation? Sinus Rhythm with 2
Premature Atrial Contractions

Cont.… PAC
When an impulse originates anywhere in
the atria and then is conducted normally
through the ventricles, the QRS will be
narrow (0.04 - 0.12 s).
14

b. Premature Ventricular Contractions(PVCs)
– Ectopic beats originate in the ventricles
resulting in wide and bizarre QRS complexes.
– When there are more than 1 premature beats
and look alike, they are called “uniform”. When
they look different, they are called “multiform”.
15

PVCs…cont
Etiology: One or more ventricular cells are
depolarizing and the impulses are
abnormally conducting through the
ventricles.
16

PVCs…cont
17
60 bpm
• Rate?
• Regularity? occasionally irreg.
none for 7th QRS
0.08 s (7th wide)
• P waves?
• QRS duration?
Interpretation? Sinus Rhythm with 1 PVC

PVCs…cont
• When an impulse originates in a ventricle,
conduction through the ventricles will be
inefficient and the QRS will be wide and bizarre.
18

Sinus Rhythms
Premature Beats
19

a. Supraventricular Arrhythmias
Atrial Fibrillation
Atrial Flutter
Paroxysmal Supraventricular Tachycardia
20

Atrial Fibrillation
Deviation from NSR
– No organized atrial depolarization, so no
normal P waves (impulses are not
originating from the sinus node).
– Atrial activity is completely chaotic
(resulting in an irregularly irregular
rate),and the AV node may be bombarded
with more than 500 impulses per minute!
21

Atrial Fibrillation cont..
• Etiology: theories says it is due to multiple re-entrant
wavelets conducted between the R & L atria.
• impulses are formed in a totally unpredictable
fashion.
• AV node allows some of the impulses to pass through
at variable intervals (so rhythm is irregularly
irregular).
• >350bpm
22

Atrial fibrillation.. cont...
23
100 bpm
• Rate?
• Regularity? irregularly irregular
none
0.06 s
• P waves?
• PR interval? none
• QRS duration?
Interpretation? Atrial Fibrillation

Atrial Flutter
Deviation from NSR
– No P waves. Instead flutter waves (note
“saw tooth” pattern) are formed at a rate
of 250 - 350 bpm.
– Only some impulses conduct through
the AV node (usually every other
impulse)
24

Atrial Flutter cont.…
Etiology: The AV node cannot handle the
extraordinary number of atrial impulses 
Reentrant pathway in the right atrium with
every other impulse generating a QRS (others
are blocked in the AV node as the node
repolarizes).
 rarely life threatening
25

Common conditions associated with atrial flutter
 Hypertension
 Obesity
 Diabetes mellitus
 Electrolyte imbalances
 Thyrotoxicosis
 coronary artery disease

Atrial Flutter cont.…
27
70 bpm
• Rate?
flutter waves
0.06 sec
• P waves?
• QRS duration?
Interpretation? Atrial Flutter

Paroxysmal Supraventricular Tachycardia
Deviation from NSR
The heart rate suddenly speeds up and the P waves are lost.
• Etiology: There are several types of PSVT but all originate above the
ventricles (therefore the QRS is narrow).
• Most common: abnormal conduction in the AV node (reentrant
circuit looping in the AV node)
• Rate: 150–250 bpm
• Regular
In most patients, the drug of choice for acute therapy is either
adenosine or verapamil.
28

PSVT….cont.
29
74 148 bpm
• Rate?
• Regularity? Regular  regular
Normal  none
0.08 s
• P waves?
• PR interval? 0.16 s  none
• QRS duration?
Interpretation? PSVT

Ventricular Arrhythmias
Ventricular Tachycardia
Ventricular Fibrillation
30

Ventricular Tachycardia
Deviation from NSR
– Impulse is originating in the ventricles (no P waves,
wide QRS).
• Etiology: There is a re-entrant pathway looping in a
ventricle (most common cause).
• Ventricular tachycardia can sometimes generate enough
cardiac output to produce a pulse; at other times no pulse
can be felt
31

VT cont.…
32
160 bpm
• Rate?
none
wide (> 0.12 sec)
• P waves?
• QRS duration?
Interpretation? Ventricular Tachycardia

Ventricular Fibrillation
Deviation from NSR
– Completely abnormal.
• Etiology: The ventricular cells are excitable and
depolarizing randomly.
• Rapid drop in cardiac output and death occurs if not
quickly reversed
33

VF cont.…
34
none
• Rate?
• Regularity? irregularly irreg.
none
wide, if recognizable
• P waves?
• QRS duration?
Interpretation? Ventricular Fibrillation

Sinus Rhythms
Premature Beats
35

AV Nodal Blocks
1st Degree AV Block
2nd Degree AV Block
 Type I
 Type II
3rd Degree AV Block
36

1st Degree AV Block
Deviation from NSR
PR Interval > 0.20 s
Etiology: Prolonged conduction delay in
the AV node or Bundle of His.
37

1st Degree AV Block cont..
38
60 bpm
• Rate?
normal
0.08 s
• P waves?
• QRS duration?
Interpretation? 1st Degree AV Block

2nd Degree AV Block, Type I
Deviation from NSR
PR interval progressively lengthens, then the impulse
is completely blocked (P wave not followed by QRS).
Etiology: Each successive atrial impulse encounters a
longer and longer delay in the AV node until one
impulse (usually the 3rd or 4th) fails to make it
through the AV node.
39

2nd Degree AV Block, Type I cont.
40
50 bpm
• Rate?
• Regularity? regularly irregular
nl, but 4th no QRS
0.08 s
• P waves?
• PR interval? lengthens
• QRS duration?
Interpretation? 2nd Degree AV Block, Type I

2nd Degree AV Block, Type II
Deviation from NSR
– Occasional P waves are completely blocked (P
wave not followed by QRS).
Etiology: Conduction is all or none (no prolongation
of PR interval); typically block occurs in the Bundle
of His.
41

2nd Degree AV Block, Type II
42
40 bpm
• Rate?
nl, 2 of 3 no QRS
0.08 s
• P waves?
• QRS duration?
Interpretation? 2nd Degree AV Block, Type II

3rd Degree AV Block
Deviation from NSR
– The P waves are completely blocked in the AV junction;
QRS complexes originate independently from below the
junction.
Etiology: There is complete block of conduction in the AV
junction, so the atria and ventricles form impulses
independently of each other. Without impulses from the
atria, the ventricles own intrinsic pacemaker kicks in at
around 30 - 45 beats/minute.
43

3rd Degree AV Block cont..
44
40 bpm
• Rate?
no relation to QRS
wide (> 0.12 s)
• P waves?
• QRS duration?
Interpretation? 3rd Degree AV Block

Bundle Branch Blocks
45

Normal Impulse Conduction
Sino atrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers
46

So, depolarization of the
Bundle Branches and Purkinje
fibers are seen as the QRS
complex on the ECG.
Therefore, a conduction block
of the Bundle Branches would
be reflected as a change in the
QRS complex.
47
Right
BBB

Bundle Branch Block
 QRS > 0.12 sec
 “Notched” QRS in
 RBBB: in V1-V2
 LBBB: in V5-V6
 Lead V1
 RBBB: Big R-wave
 LBBB: Big S-wave
 Axis
 RBBB: Right shift
 LBBB: left shift

With Bundle Branch Blocks you will see two changes on the ECG.
1. QRS complex widens (> 0.12 sec).
2. QRS morphology changes (varies depending on ECG lead,
and if it is a right vs. left bundle branch block).
49

Why does the QRS complex widen?
50
When the conduction
pathway is blocked it will
take longer for the
electrical signal to pass
throughout the ventricles.

Right Bundle Branch Blocks
51
V1
What QRS morphology is characteristic?
For RBBB the wide QRS complex assumes a unique,
virtually diagnostic shape in those leads overlying the
right ventricle (V1 and V2).
“Rabbit Ears”

Causes of right shift
 Right Hypertrophy (Cor Pulmonale)
 Left Infarction
 Left Pneumothorax

Left Bundle Branch Blocks
53
What QRS morphology is characteristic?
For LBBB the wide QRS complex assumes a characteristic
change in shape in those leads opposite the left ventricle (right
ventricular leads - V1 and V2)and big R in v5/v6.
Broad,
deep S
waves
Normal

Causes of left shift
 Obesity/Pregnancy
 Right Tension Pneumothorax
 Right Infarction
 Left Hypertrophy

55
Question ?

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56

3. common cardiac arrythemias

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