Arrythmia 411.ppt

Cardiac Arrhythmias
Dr. Ahmad Hersi

Action Potential of a Myocardial Cell
+25
0
-25
-50
-75
-100
Resting Potential
- 90 mv
Overshoot
+10 mv
Na+ Ca++
K+
0
1
2
4
Active Transport
Na+ out K+ back in
ARP RRP SNP
Corresponding ECG Overlay
Myocardium Muscle Action Potential

Normal Cardiac Cycle
Systole Diastole
Electrical Depolarization
“activate”
Repolarization
“recovery”
Mechanical Contract
“empty”
Relax
“fill”

What does it tell us?
• the electrical conduction through the heart
• areas of ischemia or myocardial damage
• LV Hypertrophy
• electrolyte disturbances / drug toxicity

The Electrical System of the Heart
AV
Node
Posterior Inferior
Fascicle
Anterior Superior
Fascicle
Septal
Depolarization
Fibers
Purkinjie Fibers
Inter- nodal
Tracts
Bundle of
HIS
Left Bundle
Branch
Right Bundle
Branch
SA
Node

SA
Node
AV
Node
Inter-nodal
Tract
Bundle
of Kent
James Fibers
Conduction System of
the Heart:
A Conceptual Model
for Illustration
Bundle
of HIS
Right
Bundle
Branch
Left
Bundle
Branch
Septal
Depolarization
Fibers
Anterior
Superior
Fascicle
Posterior
Inferior
Fascicle

SA Node – “pacemaker” of
the heart (60-100bpm)
AV Node – junction of the
atria and ventricles (40-60bpm)
Bundles – Bundle of His
connects the AV node to the
bundle branches (20-40bpm)
AV
Node
Inter- nodal
Tracts
Bundle of
HIS
SA
Node

What Is In Each Beat?
(the cardiac cycle in waves, complexes, and intervals)
• P Wave – atrial contraction or depolarization, (usually upright)
• QRS Complex – time for ventricular contraction or depolarization
(usually upright) (0.04 - 0.12sec) (delays in the bundle branches will widen the
QRS)
• T Wave – ventricular repolarization “recharging” (usually upright)
• PR Interval – time between atrial depolarization to ventricular
depolarization (beginning of P wave to beginning of QRS)(0.12 - 0.20sec)
(prolonged PR = delays in the AV node conduction)
• QT Interval – represents one complete ventricular depolarization and
repolarization (beginning of QRS to the end of the T wave) (0.32 – 0.44sec)
(disturbances are usually due to electrolyte disturbances or drug effects)

The ECG Complex with Interval and Segment Measurements

ECG Paper and related Heart Rate & Voltage Computations
Memor
ize

Reading a Rhythm Strip
What Do I Look For?
► Regularity - What is the R – R Interval?
► Rate - Is the rate normal (60-100), slow, or fast?
***Six-second strip method - (30 big boxes) & multiply times
ten
► P Wave – Is there a P wave before every QRS? Is it upright?
► QRS Complex – Is there a normal QRS complex
following each P wave? Wide or normal?
► T wave – How does your T wave look? Upright?
► Measure your intervals – PR Interval, QRS, QT

Tehran Arrhythmia Center
Pacemakers of the Heart
• SA Node - Dominant pacemaker with an
intrinsic rate of 60 - 100 beats/minute.
• AV Node - Back-up pacemaker with an
intrinsic rate of 40 - 60 beats/minute.
• Ventricular cells - Back-up pacemaker with
an intrinsic rate of 20 - 45 bpm.

Rhythm Analysis
• Step 1: Calculate rate.
• Step 2: Determine regularity.
• Step 3: Assess the P waves.
• Step 4: Determine PR interval.
• Step 5: Determine QRS duration.

Step 1: Calculate Rate
Option 1
– Count the # of R waves in a 6 second rhythm
strip, then multiply by 10.
Interpretation? 9 x 10 = 90 bpm
3 sec 3 sec

• Option 2
– Find a R wave that lands on a bold line.
– Count the # of large boxes to the next R wave.
If the second R wave is 1 large box away the
rate is 300, 2 boxes - 150, 3 boxes - 100, 4
boxes - 75, etc. (cont)
R wave

• Option 2 (cont)
– Memorize the sequence:
300 - 150 - 100 - 75 - 60 - 50
Interpretation?
3
0
0
1
5
0
1
0
0
7
5
6
0
5
0
Approx. 1 box less than
100 = 95 bpm

Step 2: Determine regularity
• Look at the R-R distances (using a caliper or
markings on a pen or paper).
• Regular (are they equidistant apart)? Occasionally
irregular? Regularly irregular? Irregularly
irregular?
Interpretation? Regular
R R

Step 3: Assess the P waves
• Are there P waves?
• Do the P waves all look alike?
• Do the P waves occur at a regular rate?
• Is there one P wave before each QRS?
Interpretation? Normal P waves with 1 P wave for
every QRS

Step 4: Determine PR interval
• Normal: 0.12 - 0.20 seconds.
(3 - 5 boxes)
Interpretation? 0.12 seconds

Step 5: QRS duration
• Normal: 0.04 - 0.12 seconds.
(1 - 3 boxes)
Interpretation? 0.08 seconds

Rhythm Summary
• Rate 90-95 bpm
• Regularity Regular
• P waves Normal
• PR interval 0.12 s
• QRS duration 0.08 s
Interpretation? Normal Sinus Rhythm

Normal Sinus Rhythm
• Normal and constant P wave contours
• Normal P wave axis
• Rate between 60 and 100 bpm

Anatomical Aspects of Normal
Sinus Node
• Located at the superior anterolateral portion
of right atrium near its border with the
superior vena cava
• It is an epicardial structure near sulcus
terminalis
• From endocardial approach the closest
approach is near the superior end of crista
terminalis

Sinus Node Function
• The dominant cardiac pacemaker
• Highly responsive to autonomic influences
• Decreasing rate with vagal stimulation
• Increasing rate with sympathetic activity
• Normal sinus rate under basal conditions is
60-100 bpm.

Sinus Tachycardia
130 bpm
• Rate?
• Regularity? Regular
Normal
0.08 s
• P waves?
• PR interval? 0.16 s
• QRS duration?
Interpretation? Sinus Tachycardia

Sinus Tachycardia
• Sinus rhythm exceeding 100 bpm in adults
• Usually between 100 and 180 bpm but may
be higher with extreme exertion
• Maximum heart arte decreases wit age from
near 200 bpm to less than 140 bpm
• Gradual onset and termination

Sinus Tachycardia

Sinus Tachycardia
Causes
• Common in infancy and childhood
• Normal response to a variety of physiological and
pathological stresses
– Exertion, anxiety
– Hypovolemia, anemia
– Fever
– Congestive heart failure
– Myocardial ischemia
– Thyrotoxicosis
• Drugs
• Inflammation

Sinus Bradycardia
30 bpm
• Rate?
normal
0.10 s
• P waves?
• QRS duration?
Interpretation? Sinus Bradycardia

Sinus Bradycardia
• Sinus rhythm at a rate less than 60 bpm
• Can result from excessive vagal or
decreased sympathetic tone as well as
anatomic changes in sinus node
• Frequently occurs in healthy young adults,
particularly well-trained athletes
• Sinus arrhythmia often coexists

Sinus Bradycardia

Sinus Bradycardia
Junctional Escape Beats

Sinus Bradycardia
Causes
• Hypothyroidism
• Drugs
• During vomiting or vasovagal syncope
• Increased intracranial pressure
• Hypoxia, hypothermia
• Depression
• Jaundice

Sinus Arrhythmia
50-75 bpm
• Rate?
• Regularity? Phasic variations
normal
0.10 s
• P waves?
• QRS duration?
Interpretation? Sinus Arrhythmia

Sinus Pause

Sick Sinus Syndrome
• A combination of symptoms (dizziness,
fatigue, confusion, syncope and congestive
heart failure) caused by sinus node dysfunction
• Atrial tachyarrhythmias may accompany
sinus node dysfunction
<bradycardia-tachycardia syndrome>

AV Block
Types
• First degree AV block
• Second degree AV block
– Mobitz type I (Wenckebach)
– Mobitz type II
• Third degree AV block (Complete heart block)
• High degree (advanced) AV block

First Degree AV Block
60 bpm
• Rate?
Normal
0.08 s
• P waves?
• QRS duration?
Interpretation? 1st Degree AV Block

PR Interval
PR interval
AV nodal blocks
Normal
High catecholamine states
Wolff-Parkinson-White
> 0.20 s
0.12-0.20 s
< 0.12 s
Wolff-Parkinson-White 1st Degree AV Block

• Conduction time is prolonged but
all impulses are conducted.
• PR interval exceeds 0.2 sec in
adults
• Site of conduction delay may be
in the AV node (most
commonly), in the His-Purkinje
system or both.

Wenckebach AV Block
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

Mobitz Type I Second Degree
AV Block
• Also called Wenckebach block
• Typical type characterized by progressive
PR prolongation culminating in a non-
conducted P wave
• Narrow QRS in most cases

Wenckebach Block
• Atypical pattern in over half the cases
• The site of block is almost always in the AV
node.
• Generally benign and does not advance to
more advanced AV block
• Can occur in normal children and well-
trained athletes

Mobitz Type II AV Block
40 bpm
• Rate?
Nl, 5th P no QRS
0.11 s
• P waves?
• QRS duration?
Interpretation? 2nd Degree AV Block, Type II

Mobitz Type II Second Degree
AV Block
• PR interval remains constant prior to the
blocked P wave
• Commonly associated with bundle branch
blocks

2:1 AV Block

2:1 AV Block
AV Nodal Level

2:1 AV Block
Infra-nodal Level

2:1 AV block
Infra-nodal Level

Complete Heart Block
40 bpm
• Rate?
No relation to QRS
Wide (> 0.12 s)
• P waves?
• PR interval? None
• QRS duration?
Interpretation? 3rd Degree AV Block

Complete AV block
• No atrial activity conducts to the ventricles
• AV dissociation is present. The atria and
ventricles are controlled by independent
pacemakers.
• Ventricular focus is usually located just
below the site of block.
• Higher sites are more stable with a more
faster escape rate.

Complete AV block

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

AV Conduction Disturbances
Etiology
• Degenerative diseases are the most common
causes
• A variety of other diseases may be
responsible: myocardial infarction, drugs,
acute infections, infiltrative diseases,
neoplasms, etc.
• Hypervagotonia

Premature Beats
• Premature Atrial Contractions
(PACs)
• Premature Ventricular Contractions
(PVCs)

PAC
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? NSR with Premature Atrial
Contractions

Narrow QRS Beats
• When an impulse originates anywhere in the
atria (SA node, atrial cells, AV node, Bundle
of His) and then is conducted normally
through the ventricles, the QRS will be
narrow (0.04 - 0.12 s).

PVC
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

Wide QRS Beats
• When an impulse originates in a ventricle,
conduction through the ventricles will be
inefficient and the QRS will be wide and
bizarre.

Ventricular Conduction
Normal
Signal moves rapidly
through the ventricles
Abnormal
Signal moves slowly
through the ventricles

Ventricular Premature Complexes
Compensatory
Pause
Interpolated VPC

Atrial Fibrillation
100 bpm
• Rate?
• Regularity? Irregularly irregular
None
0.06 s
• P waves?
• QRS duration?
Interpretation? Atrial Fibrillation

Atrial
Fibrillation

Atrial Fibrillation
• The most common sustained arrhythmia
• Incidence increases progressively with age.
• Prevalence: 0.4% of overall population
• Mortality rate double that of control
• AF is characterized by disorganized atrial
activity without discrete P waves

Atrial Fibrillation
• Undulating baseline or atrial deflections of
varying amplitude and frequency ranging
from 350 to 600 bpm.
• Irregularly irregular ventricular response.

Atrial Fibrillation
• Morbidity related to:
– Excessive ventricular rate
– Pause following cessation of AF
– Systemic embolization
– Loss of atrial kick
– Anxiety secondary to palpitations
– Irregular ventricular rate

Atrial Fibrillation
• Persistent AF usually in patients with
cardiovascular disease
– Valvular heart disease
– Hypertensive heart disease
– Congenital heart disease
• Paroxysmal AF may occur with acute hypoxia,
hypercapnia or metabolic or hemodynamic
derangements
• Normal people with emotional stress or surgery or
acute alcoholic intoxication
• Lone AF

Atrial Fibrillation
• Therapeutic Goals:
– Control of ventricular rate
– Restoration and maintenance of sinus rhythm
– Prevention of thromboembolism

CHADS2 Score and Risk of Stroke
JAMA 2001;285:2864

Atrial Flutter
70 bpm
• Rate?
Flutter waves
0.06 s
• P waves?
• QRS duration?
Interpretation? Atrial Flutter

Atrial Flutter
• Regular atrial tachyarrhythmia with atrial
rate between 250-350 bpm.
• Flutter waves are seen as saw-tooth like
atrial activity

Atrial Flutter
• Atrial Flutter is a form of atrial reentry
localized to right atrium.
• Typically the ventricular rate is half the
atrial rate, but the ventricular response may
be 4:1, 2:1, 1:1 etc.

Atrial Flutter Circuit

Atrial Flutter
• Most often in patients with organic heart
disease
• Usually less long-lived than AF and may
convert to AF.
• Control of ventricular rate is difficult in
atrial flutter
• The most effective treatment is DC
cardioversion

PSVT
74 148 bpm
• Rate?
• Regularity? Regular  regular
Normal  none
0.08 s
• P waves?
• PR interval? 0.16 s  none
• QRS duration?
Interpretation? Paroxysmal Supraventricular
Tachycardia

Paroxysmal Supraventricular
Tachycardia (PSVT)
• Usually at a rate of 150-250 bpm
• No organic heart disease in the majority
• Presentations
–Palpitations
–Chest discomfort,dyspnea, lightheadedness
–Frank syncope
–SCD

Preexcitation

VT
160 bpm
• Rate?
None
Wide (> 0.12 sec)
• P waves?
• QRS duration?
Interpretation? Ventricular Tachycardia

Ventricular Arrhythmias
Definitions
• Premature Ventricular beats
– Single beats
– Ventricular Bigeminy, the appearance of one PVC after each sinus
beat
– Couplets, two consecutive premature beats
– Triplets, three consecutive premature beats
– Salvos, runs of 3-10 premature beats
• Accelerated Idioventricular Rhythm (Slow VT), rate 60-
100 bpm
• Ventricular Tachycardia (VT), rate over 100 bpm
• Ventricular Flutter, regular large oscillations at a rate of
150-300 bpm
• Ventricular Fibrillation (VF), irregular undulations of
varying contour and amplitude

Ventricular Tachycardia
Classification
• Duration
– Sustained VT defined as VT that persists for than 30 s
or requires termination because of hemodynamic
collapse
– Nonsustained VT, 3 beats to 30 s
• Morphology
– Monomorphic
– Polymorphic

Salvos

Sustained Monomorphic VT

Sustained Polymorphic VT

VT Etiology
• VT generally accompanies some form of
structural heart disease most commonly:
– Ischemic heart disease
– Cardiomyopathies
• Primary electrical abnormalities
– Long QT syndromes
– Brugada syndrome
• Idiopathic VT

VF
None
• Rate?
• Regularity? Irregularly irreg.
None
Wide, if recognizable
• P waves?
• QRS duration?
Interpretation? Ventricular Fibrillation

Sudden Death Syndrome
• Incidence
–400,000 - 500,000/year in U.S.
–Only 2% - 15% reach the
hospital
–Half of these die before
discharge
• High recurrence rate

Clinical Substrates Associated
with VF Arrest
• Coronary artery disease
• Idiopathic cardiomyopathy
• Hypertrophic cardiomyopathy
• Long QT syndrome
• RV dysplasia
• Rarely: WPW syndrome

Arrythmia 411.ppt

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