2. – The heart has a
conduction system
separate from any other
system
– The conduction system
makes up the
PQRST complex we see on
paper
– An arrhythmia is a
disruption of the
conduction system
– Understanding how the
heart conducts normally is
essential in understanding
and identifying arrhythmias
3. • SA Node
• Inter-nodal and
inter-atrial pathways
• A-V Node
• Bundle of His
• Perkinje Fibers
4. The cardiac conduction system. Depolarisation starts in the
sinoatrial node and spreads through the atria (blue arrows), and
then through the AV node (black arrows). Depolarisation then
spreads through the bundle of His and the bundle branches to reach
the ventricular muscle (red arrows). Repolarisation is in the
opposite direction (green arrows). PQRST - The upper limit of the
normal range for each interval is given in brackets
5. The sequence of activation of the ventricles. Activation of the
septum occurs first (red arrows), followed by spreading of the
impulse through the left ventricle (blue arrows) and then the
right ventricle (green arrows).
8. • The primary pacemaker
of the heart
• Each normal beat is
initiated by the SA node
• Inherent rate of 60-100
beats per minute
• Represents the P-wave
or atrial depolarization
(firing)
Located in the septum of
the heart
– Receives impulse from
inter-nodal pathways
and holds the signal
before sending on to the
Bundle of His
– Represents the PR
segment of the QRS
complex
– Has an inherent rate
of 40-60 beats per
minute
– Acts as a back up
when the SA node fails
– Where all junctional
rhythms originate
SA NODE AV NODE
10. •ST segment
• – Ventricle
• contracting
• – Should be at
isoelectric line
• Elevation or
depression may
be important
• U wave
• – Perkinje fiber
• repolarization?
11. Normal
– Heart rate = 60 – 100 bpm
• – PR interval = 0.12 – 0.20 sec
• – QRS interval <0.12
• – SA Node discharge = 60 – 100 / min
• – AV Node discharge = 40 – 60 min
• – Ventricular Tissue discharge = 20 – 40 min
12. Cardiac cycle
– P wave = atrial depolarization
• – PR interval = pause between atrial and
• ventricular depolarization
• – QRS = ventricular depolarization
• – T wave = ventricular depolarization
14. • It may be abnormality in impulse formation or
it’s conduction
• Arrhythmia –means
Abnormal electrical
activity of the heart.
• Abnormality in
• Rate ( HR=60-100/min),
• Rhythm (normal sinus, may be
atrial ,nodal/junctional, ventricular)
• Conduction (SA,AVN,BBB)
DEFINITION
15. Mechanisms of Cardiac Arrhythmias
• Mechanisms of bradycardia:
• Sinus bradycardia is a result of abnormally slow
automaticity while bradycardia due to AV block is caused
by abnormal conduction within the AV node or His bundle.
the distal AV conduction system.
• Mechanisms generating tachycardia include:
• - Accelerated automaticity- S.T. & Accellerated
JunctionalTachy
• -Triggered activity.
• - Re-entry (or circus movements)
16. Re-entry (or circus movement)
• The mechanism of re-entry occurs when a 'ring' of
cardiac tissue having 2 different pathway surrounds an
in-excitable core e.g. in a region of scarred
myocardium.
• Alfa/fast pathway is rapid conducting & slow recovery
and
• Beta pathway/slow pathway is slow conducting and
rapid recovery .
17. Mechanism of re-entry. Re-entry can occur when there are two alternative pathways
with different conducting properties (e.g. the AV node and an accessory pathway, or
an area of normal tissue and an area of ischaemic tissue). In this example, pathway A
conducts slowly and recovers quickly while pathway B conducts rapidly and recovers
slowly. (1) In sinus rhythm each impulse passes down both pathways before entering a
common distal pathway. (2) As the pathways recover at different rates a premature
impulse may find pathway A open and B closed. (3) Pathway B may recover while the
premature impulse travels selectively down pathway A. The impulse may then travel
retrogradely up pathway B, setting up a closed loop or re-entry circuit. (4) This may
initiate a tachycardia that will continue until the circuit is interrupted by a change in
conduction rates or electrical depolarisation.
21. Normal Sinus Rhythm
HR RHYTHM P WAVE PR INTERVAL
IN SEC
QRS
IN SEC
60-100 BPM REGULAR BEFORE EACH
QRS , IDENTICAL
0.12 - 0.20 < 0.12
22. Normal Sinus Rhythm
• – Sinus Node is the primary pacemaker
• – One upright uniform p-wave for every QRS
• – Rhythm is regular
• – Rate is between 60-100 beats per minute
24. Sinus Bradycardia
– One upright uniform p-wave for every QRS
• – Rhythm is regular
• – Rate less than 60 beats per minute
• SA node firing slower than normal
• Normal for many individuals
• Identify what is normal heart rate for patient
26. Sinus Tachycardia
– One upright uniform p-wave for every QRS
• – Rhythm is regular
• – Rate is greater than 100 beats per minute
• Usually between 100-160 (>160 SVT)
• Can be high due to anxiety, stress, fever,
medications (anything that increases oxygen
consumption)
27. Sinus Arrhythmia
HR RHYTHM P WAVE PR INTERVAL QRS
VAR IRREGULAR BEFORE QRS 0.12 - 0.20 < 0.12
Sinus arrhythmia of young man and children.
Respiratory or nonrespiratory variation of HR .
In inspiration rate is higher .
Variation of HR > 10 %
28. Sinus Arrhythmia
-- One upright uniform p-wave for every QRS
• Rhythm is irregular
• Rate increases as the patient breathes in
• Rate decreases as the patient breathes out
• Rate is usually 60-100 (may be slower)
• Variation of normal, not life threatening
29. Sinus Pause
Cause: SSS.
HR RHYT
HM
P
WAVE
PR
INTER
VAL
QRS
NA IRR BEFO
RE
QRS
0.12-
0.20
<0.12
SINUS ARREST S.A BLOCK
PP/ RR interval is exactly double
of normal PP/RR interval
30. Sinus Rhythms
• Sinus Arrest
• Stop of sinus rhythm
• New rhythm starts
• One dropped beat is a sinus pause
• Beats walk through
33. Premature Atrial
Contraction (PAC)
• One P-wave for every QRS
• P-wave may have different morphology on
ectopic beat, but it will be present
• Single ectopic beat will disrupt regularity of
underlying rhythm
• Rate will depend on underlying rhythm
• Underlying rhythm must be identified
• Classified as rare, occasional, or frequent
PAC’s based on frequency
34. SVT
• INCLUDES----
1) ST
• 2) AT
• 3) AJT
• 4) AVNRT
• 5) AVRT
• 6) ATRIAL FLUTTER
• 7) AF Supraventricular tachycardia. The
rate is 180/min and the QRS
complexes are normal
35. Sign-symptoms of SVT
• Palpitation.
• Dizziness, Blurring vision.
• Vertigo.
• Chest Pain ( due to reduced coronary flow).
• Sweating. Cold –clammy extremities.
• Pre-syncope ( due to reduced cerebral
circulation)
• Syncope ( due to reduced cerebral circulation)
• Rapid onset , may suddenly disappears
without Rx or by vomiting.
36. AVNRT
4times more common
than AVRT.
-- Mostly in younger
people
with structurally normal
heart.
• Metabolic factors,
anxiety,
coffee, tea may ppt. the
condition ( not the cause)
AVRT – IN
WPW
SYNDROME
--Macro re-entrance
tachycardia. a/w WPW
synd.
--Resting ECG may
show
Delta wave/ pre-
excitation.
--Nearly impossible to
differentiate from
AVNRTECG
37. SVT
SVT ECG REMARKS
AVNRT RAPID RATE ( 150-250)
NO P WAVE
NORMAL QRS
IN YOUNG PEPLE
EPISODIC , RAPID ONSET ,
RAPID RECOVERY,
RECURRENT
AVRT DO DO
38. Atrial Fibrillation
CAUSES OF AF
-RHD ( mc )
-HYPERTENSIVE HEART DISEASE
-IHD
-THYROTOXICOSIS
-LONE AF
-ASD
-PULM EMBOLISM
-ALCOHOL
-METABOLIC
39. • Disorganised atrial activity and irregular AV
conduction.
• International consensus on nomenclature and
classification of AF:
• Initial ( First detected) event.
• Paroxysmal that terminates spontaneously
within 48 hrs. it may recur.
• Persistent – not self limiting, and lasting >7 days
or after cardio version.
• Permanent( established)- may or may not be
terminated or relapse after cardio version.
• (This classification is for guideline of therapy).
40. HR RHYTHM P WAVE PR INT QRS
VAR IRR ABSENT, R/B
WAVY ,
IRREGULAR
FIBRILLARY
WAVES
NA < 0.12
42. Atrial Fibrillation
• No discernable p-waves preceding the QRS complex
• The atria are not depolarizing effectively, but
fibrillating
• Rhythm is grossly irregular
• If the heart rate is <100 it is considered controlled
a-fib, if >100 it is considered to have a “rapid
ventricular response”
• AV node acts as a “filter”, blocking out most of the
impulses sent by the atria in an attempt to control
the heart rate
43. Atrial Tachycardia
HR RHYTHM P WAVE PR INTERVAL QRS
140- 250 REGULAR PRESENT BUT
ABNORMAL,
HIDDEN ON ST
SEGMENT OR T
WAVE
NA WIDE
< 0.12
46. Atrial Flutter
• More than one p-wave for every QRS complex
• Demonstrate a “sawtooth” appearance
• Atrial rhythm is irregular. Ventricular rhythm will
be regular if the AV node conducts consistently. If
the pattern varies, the ventricular rate will be
irregular
• Rate will depend on the ratio of impulses
conducted through ventricles
• Atrial flutter is classified as a ratio of pwaves
per QRS complexes (ex: 3:1 flutter
3 p-waves for each QRS)
47. Paroxysmal SVT
• Reentry in vast majority of cases
• AV nodal reentrant tachycardia (AVNRT) and
atrioventricular reentrant tachycardia (AVRT)
• Regular, narrow QRS complexes (120-250/min).
Initiated by atrial ectopic beat
• Carotid sinus massage may terminate an episode
• Adenosine IV, radiofrequency ablation
• Multifocal atrial tachycardia (MAT)
48. Premature Junctional Contraction PJC
HR RHYTHM P WAVE PR INTERVAL QRS
USUALLY
NORMAL
IRREGULAR PREMATURE,
ABNORMAL,
INVERTED OR
HIDDEN
SHORT < 0.12 NORMAL
< 0.12
49. Premature Junctional Contraction (PJC)
• P-wave can come before or after the QRS
complex, or it may lost in the QRS complex
• If visible, the p-wave will be inverted
• Rhythm will be irregular due to single ectopic beat
• Heart rate will depend on underlying rhythm
• Underlying rhythm must be identified
• Classify as rare, occasional, or frequent PJC
based on frequency
• Atria are depolarized via retrograde conduction
50. Accelerated Junctional Rhythm
Accelerated Junctional Rhythm
– P-wave can come before or
after the QRS complex, or lost
within the QRS complex
• If p-waves are seen they will be
inverted
– Rhythm is regular
– Heart rate between 60-100
beats per minute
• Within the normal HR range
• Fast rate for the junction
(normally 40-60 bpm)
52. Junctional Tachycardia
• P-wave can come before or after the QRS
complex or lost within the QRS entirely
• If a p-wave is seen it will be inverted
• Rhythm is regular
• Rate is between 100-180 beats per minute
• In the tachycardia range, but not originating
from SA node
• AV node has speed up to override the SA
node for control of the heart
53. Junctional Escape
HR RHYTHM P WAVE PR INTERVAL QRS
40- 60 REGULAR ABSENT /
INVERTED /
AFTER QRS
SHORT
< 0.12
NORMAL
54. Junctional Escape Rhythm
• P-wave may come before or after the QRS
or may be hidden in the QRS entirely
• If p-waves are seen, they will be inverted
• Rhythm is regular
• Rate 40-60 beats per minute
• The SA node has failed; the AV junction takes
over control of the heart
56. Premature Ventricular Contraction
(PVC)
• The ectopic beat is not preceded by a p-wave
• Irregular rhythm due to ectopic beat
• Rate will be determined by the underlying
rhythm
• QRS is wide and may be bizarre in appearance
• Caused by a irritable focus within the ventricle
which fires prematurely
• Must identify an underlying rhythm
57. Premature Ventricular Contraction
– Classify as rare, occasional, or frequent
– Classify as unifocal, or multifocal PVC’s
• Unifocal-originating from same area of the
ventricle; distinguished by same morphology
58. Premature Ventricular Contraction
– Classify as unifocal, or multifocal PVC’s
– Unifocal-originating from same area of the
ventricle; distinguished by same morphology
– Multifocal-originating from different areas of the
ventricle; distinguished by different morphology
65. Ventricular Tachycardia
• No discernable p-waves with QRS
• Rhythm is regular
• Atrial rate cannot be determined,
• ventricular rate is between 150-250 beats
per minute
• Must see 4 beats in a row to classify as vtach
• Is a deadly rhythm
67. Ventricular Fibrillation
• No discernable p-waves
• No regularity
• Unable to determine rate
• Multiple irritable foci within the ventricles all
firing simultaneously
• May be coarse or fine
• This is a deadly rhythm
69. Asystole
HR RHYTHM P WAVE PR INTERVAL QRS
------ -------- -------- -------- --------
No p-waves
• No regularity
• No Rate
• This rhythm is associated with
death
71. First Degree Heart Block
HR RHYTHM P WAVE PR INTERVAL QRS
NORMAL REGULAR BEFORE EACH
QRS ,
IDENTICAL
> 0.20 < 0.12
72. First Degree Heart Block
• P-wave for every QRS
• Rhythm is regular
• Rate may vary
• Av Node hold each impulse longer than normal
before conducting normally through the
ventricles
• Uniformly Prolonged PR interval
• Looks just like normal sinus rhythm
• A misnomer as conduction not blocked but
delayed
73. Second Degree Heart Block
Mobitz Type I (Wenckebach)
HR RHYTHM P WAVE PR INTERVAL QRS
NORMAL /
SLOW
IRREGULAR PRESENT BT
MAY NOT F/B
QRS
PROGRESSIVE
LY LONGER
< 0.12
74. Second Degree Heart Block
Mobitz Type I (Wenckebach
pattern)
• Some p-waves are not followed by QRS
• Rhythm is irregular
• R-R interval is in a pattern of grouped beating
• Rate 60-100 bpm
• Intermittent Block at the AV Node
• Progressively prolonged p-r interval until a QRS
is blocked completely
75. Second Degree Heart Block
Mobitz Type II (Classical)
HR RHYTHM P WAVE PR INTERVAL QRS
USUALLY SLOW REGULAR /
IRREGULAR
2,3 OR 4
BEFORE EACH
QRS ,
IDENTICAL
0.12 - 0.20 < 0.12
76. Second Degree Heart Block
Mobitz Type II (Classical)
• More p-waves than QRS complexes
• Rhythm is irregular
• Atrial rate 60-100 bpm; Ventricular rate 30-
100bpm (depending on the ratio on
conduction)
• Intermittent block at the AV node
• AV node normally conducts some beats while
blocking others…..Sudden conduction failure
77. Third Degree Heart Block
(Complete)
HR RHYTHM P WAVE PR INTERVAL QRS
30 - 60 REGULAR PRESENT BUT
NO
CORRELATION
TO QRS, OR
HIDDEN
VARIES < 0.12
78. Third Degree Heart Block
(Complete)
• There are more p-waves than QRS complexes
• Both P-P and R-R intervals are regular
• Atrial rate within normal range; Ventricular
rate between 20-60 bpm
• The block at the AV node is complete
• There is no relationship between the p-waves
and QRS complexes
79. Right Bundle Branch Blocks
• RBBB occurs with such
conditions as anterior
wall MI
• QRS complex is greater
than 0.12 second and
has a different
configuration,
• sometimes resembling
rabbit ears or the
letter “M.”
80. RBBB- QRS are wide, RSR’ pattern in
V1-2 , deep S in lateral leads, secondary
ST-T
changes in V1-3.
81. Left Bundle Branch Blocks
• Left bundle-branch
block (LBBB) never
occurs normally.
• This block is usually
caused by
hypertensive heart
disease, aortic
stenosis,
degenerative
changes of the
conduction system.
82. LBBB – QRS is wide , Mor RsR
pattern in V5-6. Secondary ST-T
changes in lateral leads.
There may be LAD.
83. • AV bypass tract present,
leading to recurrent
arrhythmias
• Preexcitation – delta waves,
short PR interval with broad
QRS on ECG during sinus
rhythm
• Risk of SVT, VF, VT
• Radiofrequency ablation of
abnormal tracts
Wolff-Parkinson-White (WPW)
syndrome
84. Wolff-Parkinson-White syndrome. In this condition there is
a strip of accessory conducting tissue that allows electricity to
bypass the AV node and spread from the atria to the ventricles
rapidly and without delay. When the ventricles are depolarised
through the AV node (1) the ECG is normal, but when the
ventricles are depolarised through the accessory conducting tissue
(2) the ECG shows a very short PR interval and a broad QRS
complex. ; the characteristic slurring of the upstroke of the QRS
complex is known as a delta wave. Orthodromic tachycardia. This
is the most common form of tachycardia in WPW. The re-entry
circuit passes antegradely through the AV node and retrogradely
through the accessory pathway. The ventricles are therefore
depolarised in the normal way, producing a narrow-complex
tachycardia that is indistinguishable from other forms of SVT.
Antidromic tachycardia. Occasionally, the re-entry circuit passes
antegradely through the accessory pathway and retrogradely
through the AV node. The ventricles are then depolarised through
the accessory pathway, producing a broad-complex tachycardia.
85. Torsades de pointes
• VT with polymorphic QRS
• Associated with QT prolongation
• Hypokalaemia, hypomagnesaemia
• Quinidine, phenothiazines, tricyclics, III degree
AV block, congenital
86. • This is a type of short duration tachycardia that reverts to sinus
rhythm
• spontaneously.
• It may be due to:
• - Congenital
• - Electrolyte disorders e.g. hypokalemia, hypomagnesemia,
hypocalcemia.
• - Drugs e.g. tricyclic antidepressant, class IA and III antiarrhythmics.
• It may present with syncopal attacks and occasionally ventricular
fibrillation.
• QRS complexes are irregular and rapid that twist around the baseline.
In between the spells of tachycardia the ECG show prolonged QT
interval.
• Treatment includes; correction of any electrolyte disturbances,
stopping of causative drug, atrial or ventricular pacing, Magnesium
sulphate
87. Torsades de pointes. A bradycardia with a long QT
interval is followed by polymorphic ventricular
tachycardia that is triggered by an R on T ectopic.
