EKG Plain Simple Plain and Simple CHAPTER Third Edition Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Electrophysiology 2

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Media Directory Slide 31 Inherent Rates Animation

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. EllisDepolarization Change in the cardiac cell’s electrical charge from negative to positive Accomplished by sodium and potassium ions changing place Causes a wave of electrical charge to course from cell to cell, resulting in a discharge of electricity

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. EllisRepolarization Return of the cardiac cell to its electrically negative charge Accomplished by way of the sodium- potassium pump, an active transport system

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-1 Depolarization and Repolarization

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Electrical vs. Mechanical Depolarization and repolarization — myocardium’s electrical stimuli Contraction and relaxation — mechanical response to that stimuli Depolarization should result in heart muscle contraction Repolarization should result in relaxation

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Electrical vs. Mechanical Electrical stimulus precedes mechanical response There will be NO HEART BEAT without first having had depolarization But electrical stimulus does not guarantee mechanical response There could be a mechanical problem making the myocardium incapable of pumping

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Action Potential Phase 4: Cardiac cell at rest Phase 0: Depolarization Phases 1 & 2: Early repolarization Phase 2: Plateau phase Phase 3: Rapid repolarization

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-2 Action Potential

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Refractory Periods Absolute: No stimulus can cause depolarization Relative: Strong stimulus can cause depolarization Supernormal period: Even a weak stimulus can cause depolarization

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-3 Refractory Periods

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis EKG Waves and Complexes P wave: Atrial depolarization T a wave: Atrial repolarization. Not usually seen, as it occurs simultaneous with QRS QRS complex: Ventricular depolarization T wave: Ventricular repolarization U wave: Late ventricular repolarization. Not usually seen

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-4 EKG Waves and Complexes

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis EKG Waves and Complexes Each P-QRS-T sequence is one heart beat

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. EllisSegments PR segment: Flat line between P wave and QRS complex ST segment: Flat line between QRS complex and T wave

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. EllisBaseline The flat line between the T wave of one beat and the P wave of the next beat Also called isoelectric line

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Waves and Complexes Identification Practice 1

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Waves and Complexes Identification Practice 2

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Waves and Complexes Identification Practice 3

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Waves and Complexes Identification Practice 4

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Waves and Complexes Identification Practice 5

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis QRS Nomenclature Q wave: Downward wave preceding an upward wave R wave: Any upward wave S wave: Downward wave following an R wave QS wave: Downward wave with no upward wave at all

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-5 Examples of QRS Complexes

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis QRS Nomenclature Practice

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Cardiac Conduction System Pathway of specialized cells that create and conduct electrical impulses

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-6 Cardiac Conduction System

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Conduction Pathway Sinus node  interatrial tracts  atrium  internodal tracts  AV node  bundle of His  bundle branches  Purkinje fibers  ventricle

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Characteristics of Cardiac Cells Automaticity: Ability to create an impulse without outside stimulation Conductivity: Ability to conduct an impulse to neighboring cells Excitability: Ability to depolarize

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Characteristics of Cardiac Cells Contractility: Ability to contract Automaticity, conductivity, and excitability are electrical characteristics. Contractility is mechanical

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Pacemaker Cells Pacemaker: Area of the conduction system that initiates the electrical impulses –Sinus node: Heart’s normal pacemaker. Inherent rate 60–100 beats per minute –AV junction: Backup pacemaker. Inherent rate 40–60 beats per minute –Ventricle: A lower backup pacemaker. Inherent rate 20–40 beats per minute

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Inherent Rates Animation Click on the screenshot to view an animation showing inherent rates. Click again to pause the animation. Back to Directory

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-7 Normal Conduction

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-8 Sinus Fails, AV Junction Escapes

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-9 All Higher Pacemakers Fail, Ventricle Escapes

Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Plain and Simple, Third Edition Karen M. Ellis Figure 2-10 Block in Conduction, AV Junction Escapes