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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


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


Conditions of Conditions of ReentryReentry

Conditions of Conditions of ReentryReentry


ReentryReentryReentryReentry

Substrate + Trigger = ReentrySubstrate + Trigger = Reentry


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


BradycardiasBradycardiasImpulse ConductionImpulse Conduction

DisordersDisordersImpulse ConductionImpulse Conduction

DisordersDisorders



Classification Based on DisorderClassification Based on Disorder



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



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





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



Sinus BradycardiaSinus Bradycardia Sinus BradycardiaSinus Bradycardia





Impulse ConductionImpulse ConductionDisordersDisorders S-A BlockS-A Block



Sinus BradycardiaSinus Bradycardia Sinus BradycardiaSinus Bradycardia






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.

Health & Medicine

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