The The ElectrocardiograElectrocardiogra

mmCharles E. Wood, Ph.D.Charles E. Wood, Ph.D.

Willem Einthoven receives Nobel Prize

The EKG is not only the oldest but, in fact, over 100 years after its introduction, continues as the most commonly used cardiovascular laboratory procedure.

Resting membrane Resting membrane potentialpotential

The Nernst Equation: EK= -61.5 log (Ki/Ko)

[K+]i=135 mEq/L

- - - -

++++

Cellular Action Cellular Action PotentialsPotentials

Spread of the Action Spread of the Action PotentialPotential

Figure 11-4. Copyright 2000, WB Saunders Company, All Rights Reserved

Instantaneous potentials developed Instantaneous potentials developed on the surface of a cardiac muscle on the surface of a cardiac muscle

mass.mass.

Recording depolarization Recording depolarization and repolarization waves and repolarization waves

Zero voltage - Isoelectric pointResting stage - Polarized

Figure 11-5. Copyright 2000, WB Saunders Company, All Rights Reserved

Flow of current in the chest Flow of current in the chest around partially depolarized around partially depolarized

ventricles.ventricles.

The Wave of The Wave of DepolarizationDepolarization

ECG and MechanicsECG and Mechanics

Vector Algebraic AnalysisVector Algebraic Analysis

Vector Analysis, cont’dVector Analysis, cont’d

Summary of Limb LeadsSummary of Limb Leads

The Precordial (Chest) The Precordial (Chest) LeadsLeads

Vector Algebraic AnalysisVector Algebraic Analysis

Vector Analysis, cont’dVector Analysis, cont’d

Current Flow PatternsCurrent Flow Patterns

Sinoatrial Node

Atrioventricular Node

Time relationships between Time relationships between developed force and the changes developed force and the changes in transmembrane potentials in a in transmembrane potentials in a thin strip of ventricular musclethin strip of ventricular muscle

Time

Mechanical

event

Electricalevent

ECG and MechanicsECG and Mechanics

Modulation of the Slow-Modulation of the Slow-Response (Nodal) Action Response (Nodal) Action

PotentialsPotentials

The Wave of The Wave of DepolarizationDepolarization

Types of cardiac Types of cardiac arrhythmiasarrhythmias

BradyarrhythmiasBradyarrhythmias Escape rhythmsEscape rhythms AV blockAV block Premature contractionsPremature contractions Supraventricular tachyarrhythmiasSupraventricular tachyarrhythmias Ventricular tachyarrhythmiasVentricular tachyarrhythmias

BradyarrhythmiasBradyarrhythmias

Sinus bradycardiaSinus bradycardia Sinus pausesSinus pauses Escape rhythmsEscape rhythms

JunctionalJunctional IdioventricularIdioventricular

Sinus rhythmSinus rhythm

Figure 13-2. Copyright 2000, WB Saunders Company, All Rights Reserved

Sinus bradycardia (lead Sinus bradycardia (lead III).III).

MenuMenu FFBB

Figure 13-5. Copyright 2000, WB Saunders Company, All Rights Reserved

Prolonged P-R interval Prolonged P-R interval caused caused

by first degree heart by first degree heart block (lead II)block (lead II)

MenuMenu FFBB

Mobitz type II AV blockMobitz type II AV block

Complete AV blockComplete AV block

Figure 13-1. Copyright 2000, WB Saunders Company, All Rights Reserved

Sinus tachycardia (lead Sinus tachycardia (lead I)I)

MenuMenu FF

Atrial tachycardia with Atrial tachycardia with 2:1 conduction2:1 conduction

Ventricular preexcitation Ventricular preexcitation (WPW)(WPW)

Tachycardia circuits in Tachycardia circuits in Wolff-Parkinson-White Wolff-Parkinson-White

syndromesyndrome