Normal ECGNormal ECG
Normal ECGNormal ECG
Underlying MechanismsUnderlying Mechanisms
Impulse Formation
Impulse Formation
Impulse ConductionImpulse ConductionImpulse ConductionImpulse Conduction
Abnormal AutomaticityAbnormal Automaticity Abnormal AutomaticityAbnormal Automaticity
Slow or BlockedSlow or Blocked ConductionConduction
Slow or BlockedSlow or Blocked ConductionConduction
Triggered ActivityTriggered Activity Triggered ActivityTriggered Activity
• Reentry• Reentry
Mechanisms of Rhythm Mechanisms of Rhythm DisordersDisorders
Triggered ActivityTriggered Activity
• Afterpotentials occurring in Phase 3 (early) or 4 (late) of action potential
• Can trigger arrhythmias
• Afterpotentials occurring in Phase 3 (early) or 4 (late) of action potential
• Can trigger arrhythmias
Mechanisms of Rhythm Mechanisms of Rhythm DisordersDisorders
Early Early Afterdepolarization Afterdepolarization
Potential Causes:Potential Causes:- Low potassium - Low potassium blood levelsblood levels- Slow heart rate- Slow heart rate- Drug toxicity (ex. - Drug toxicity (ex. QuinidineQuinidine causing Torsades causing Torsades de Pointes)de Pointes)
Late Late AfterdepolarizationAfterdepolarization
Potential Causes:Potential Causes:Premature beatsPremature beatsIncreased calcium Increased calcium
blood levelsblood levelsIncreased adrenaline Increased adrenaline
levelslevelsDigitalis toxicityDigitalis toxicity
Mechanisms of Rhythm Mechanisms of Rhythm DisordersDisorders Triggered ActivityTriggered Activity
ERP - Effective ERP - Effective Refractory PeriodRefractory Period
Phases 0, 1, 2 and Phases 0, 1, 2 and early Phase 3early Phase 3
A depolarization A depolarization cannot be initiated cannot be initiated
by an impulse of any by an impulse of any strengthstrength
Action Potential of a Cardiac Action Potential of a Cardiac CellCell
Refractory PeriodsRefractory Periods
RRP - Relative RRP - Relative Refractory PeriodRefractory Period
Late Phase 3 and Late Phase 3 and early Phase 4early Phase 4
A strong impulse A strong impulse can cause can cause
depolarization, depolarization, possibly with possibly with
aberrancyaberrancy
Refractory PeriodsRefractory Periods
Action Potential of a Cardiac Action Potential of a Cardiac CellCell
Mechanisms of Rhythm Mechanisms of Rhythm DisordersDisorders
Conditions of Conditions of ReentryReentry
Conditions of Conditions of ReentryReentry
Mechanisms of Rhythm Mechanisms of Rhythm DisordersDisorders
ReentryReentryReentryReentry
Substrate + Trigger = ReentrySubstrate + Trigger = Reentry
Mechanisms of Rhythm Mechanisms of Rhythm DisordersDisorders
ReentryReentryReentryReentry
Causes of Rhythm DisordersCauses of Rhythm Disorders
Congenital•Present at birth due to genetics,
environment
Congenital•Present at birth due to genetics,
environment
Heart Disease•Myocardial Infarction,
Cardiomyopathy, High Blood Pressure
Heart Disease•Myocardial Infarction,
Cardiomyopathy, High Blood Pressure
Chemically InducedChemically Induced Diet Pills, Cold Medicine, Illegal Diet Pills, Cold Medicine, Illegal
Drugs, Caffeine, Tobacco, AlcoholDrugs, Caffeine, Tobacco, Alcohol
Chemically InducedChemically InducedDiet Pills, Cold Medicine, Illegal Diet Pills, Cold Medicine, Illegal
Drugs, Caffeine, Tobacco, AlcoholDrugs, Caffeine, Tobacco, Alcohol
Causes of Rhythm DisordersCauses of Rhythm Disorders
Secondary to other conditionsSecondary to other conditionsHyper-ThyroidHyper-ThyroidNeurocardiogenic SyncopeNeurocardiogenic Syncope
- Hypersensitive Carotid Sinus Syndrome - Hypersensitive Carotid Sinus Syndrome (CSS)(CSS)
- Vasovagal Syncope (VS)- Vasovagal Syncope (VS)
Secondary to other conditionsSecondary to other conditionsHyper-ThyroidHyper-ThyroidNeurocardiogenic SyncopeNeurocardiogenic Syncope
- Hypersensitive Carotid Sinus Syndrome - Hypersensitive Carotid Sinus Syndrome (CSS)(CSS)
- Vasovagal Syncope (VS)- Vasovagal Syncope (VS)
RBBB
RBBB
Diagnostic criteria1 QRS ≥ 0.12 s with slurring in the mid-final portion of the QRS.2 V1: rsR′ pattern with a slurred R wave and a negativeT wave.3 V6: qRs pattern with S-wave slurring and a positive T wave.4 aVR: QR with evident R-wave slurring and a negative T wave.5 T wave with polarity opposite to that of the slurred component of the QRS.
Partial or first-degree RBBBIn this case, activation delay of the ventricle is less delayed. The QRS complex is 0.1–0.12 s in duration, but V1 morphology is rsR′ or rsr′.
LBBB
Diagnostic criteria1 QRS ≥ 0.12 s, sometimes over 0.16 s, especially with slurring in the mid-portion of the QRS.2 V1: QS or rS pattern with a small r wave and a positive T wave.3 I and V6: a single R wave with its peak after the initial 0.06 s (delayed intrinsicoid deflection).4 aVR: a QS pattern with a positive T wave.5 T waves with their polarity usually opposite to the slurred component of the QRS complex.
LBBB
Diagnostic criteria1 QRS complex duration < 0.12 s.2 ÂQRS deviated to the left (mainly between –45° and –75°).3 I and aVL: qR, in advanced cases with slurring especially of the descending part of R wave.4 II, III and aVF: rS with SIII > SII and RII > RIII.5 S wave seen up to V6.
LAHB
Diagnostic criteria1 QRS complex duration < 0.12 s.2 ÂQRS shifted to the right (between +90° and +140°).3 I and aVL: RS or rS pattern.4 II, III and aVF: qR morphology.5 Precordial leads: S waves up to V6.
Must first exclude (on clinical or other grounds) other causes of right axis deviation such as cor pulmonale, pulmonary heart disease, pulmonary hypertension, etc., because these conditions can result in the identical ECG picture!
(A) An example of left posterior hemiblock. (B) The ECG ofsame patient some days before. The sudden appearance of ÂQRS shifted tothe right confirms the diagnosis of LPH
LPHB
(A) Right bundle branch block plus left anterior hemiblock and, the following day, (B) right bundle branch block plus left posterior hemiblock
Nonspecific Intraventricular Nonspecific Intraventricular Conduction Defects (IVCD)Conduction Defects (IVCD)
QRS duration >0.10s indicating slowed QRS duration >0.10s indicating slowed conduction in the ventriclesconduction in the ventricles
Criteria for specific bundle branch or fascicular Criteria for specific bundle branch or fascicular blocks not metblocks not met
Causes of nonspecific IVCD's include:Causes of nonspecific IVCD's include: Ventricular hypertrophy (especially LVH) Ventricular hypertrophy (especially LVH) Myocardial infarction (so called Myocardial infarction (so called periinfarction periinfarction
blocksblocks) ) Drugs, especially class IA and IC antiarrhythmics Drugs, especially class IA and IC antiarrhythmics
(e.g., quinidine, flecainide) (e.g., quinidine, flecainide) HyperkalemiaHyperkalemia
Bradyarrhythmia Bradyarrhythmia ClassificationsClassificationsClassification Based on DisorderClassification Based on Disorder
Impulse FormationDisorders
Impulse FormationDisorders
BradycardiasBradycardiasImpulse ConductionImpulse Conduction
DisordersDisordersImpulse ConductionImpulse Conduction
DisordersDisorders
Impulse FormationDisorders
Impulse FormationDisorders
Classification Based on DisorderClassification Based on Disorder
Impulse FormationDisorders
Impulse FormationDisorders
Impulse ConductionImpulse ConductionDisordersDisorders
Impulse ConductionImpulse ConductionDisordersDisorders
Sinus ArrestSinus Arrest Sinus ArrestSinus Arrest
Bradyarrhythmia Bradyarrhythmia ClassificationsClassifications
Sinus Node emits energy very slowlySinus Node emits energy very slowly
Sinus BradycardiaSinus Bradycardia
Classification Based on Disorder Classification Based on Disorder
Bradyarrhythmia Bradyarrhythmia ClassificationsClassifications
Sinus ArrestSinus Arrest Sinus ArrestSinus Arrest
Exit BlockExit Block Exit BlockExit Block
Sinus BradycardiaSinus Bradycardia Sinus BradycardiaSinus Bradycardia Brady/Tachy SyndromeBrady/Tachy Syndrome Brady/Tachy SyndromeBrady/Tachy Syndrome
11stst Degree AV Block Degree AV Block 11stst Degree AV Block Degree AV Block
22ndnd Degree AV Block Degree AV Block 22ndnd Degree AV Block Degree AV Block
33rdrd Degree AV Block Degree AV Block 33rdrd Degree AV Block Degree AV Block
Impulse FormationDisorders
Impulse FormationDisorders
Impulse ConductionImpulse ConductionDisordersDisorders
Impulse ConductionImpulse ConductionDisordersDisorders
Failure of sinus node dischargeFailure of sinus node discharge Absence of atrial depolarizationAbsence of atrial depolarizationPeriods of asystolePeriods of asystole
Failure of sinus node dischargeFailure of sinus node discharge Absence of atrial depolarizationAbsence of atrial depolarizationPeriods of asystolePeriods of asystole
Sinus ArrestSinus Arrest*Animatio
n
Transient block of impulses from the Transient block of impulses from the SA nodeSA node
Identified by P-P interval relationshipIdentified by P-P interval relationship
Transient block of impulses from the Transient block of impulses from the SA nodeSA node
Identified by P-P interval relationshipIdentified by P-P interval relationship
Exit BlockExit Block
Classification Based on Disorder Classification Based on Disorder
Sinus ArrestSinus Arrest Sinus ArrestSinus Arrest
Sinus BradycardiaSinus Bradycardia Sinus BradycardiaSinus Bradycardia
Bradyarrhythmia Bradyarrhythmia ClassificationsClassifications
Impulse FormationDisorders
Impulse FormationDisorders
Impulse ConductionImpulse ConductionDisordersDisorders
Impulse ConductionImpulse ConductionDisordersDisorders S-A BlockS-A Block
Classification Based on Disorder Classification Based on Disorder
Sinus ArrestSinus Arrest Sinus ArrestSinus Arrest
Sinus BradycardiaSinus Bradycardia Sinus BradycardiaSinus Bradycardia
Bradyarrhythmia Bradyarrhythmia ClassificationsClassifications
Impulse FormationDisorders
Impulse FormationDisorders
Impulse ConductionImpulse ConductionDisordersDisorders
Impulse ConductionImpulse ConductionDisordersDisorders
S-A BlockS-A Block A-V BlockA-V Block
1 degree1 degree 2 degree2 degree
Type1Type1 Type2Type2 2:1 A-V Block2:1 A-V Block High degreeHigh degree
3 degree 3 degree (complete)(complete)
Normal or
Or>.12
(A) An example of left anterior hemiblock. (B) SI SII SIII pattern. See in this case SII > SIII and there is S in lead I.