CHAPTER 1 3 



Electrocardiography 



HANS SCHAEFER 

 HANS G. HAAS 



Department of Physiology, University of Heidelberg, Heidelberg, Germany 



CHAPTER CONTENTS 



Technical Remarks 



The Ideal Electric Field of a Single Cardiac Fiber 



Vector Theory of the Electrocardiogram 



Superposition of Dipoles and Their Fields 



Limits of Applicability of Simple Vectorial Concept 



The Single Dipolc Concept of the Electrocardiogram 



The Image Surface 



Lead Fields 



Discussion of the Vectorial Concept 

 Different Lead Systems 



Total or Heart Vector Leads 



Local Leads. Theory of Unipolar Leads 

 Leads in Direct Contact With the Myocardium 

 Spread of Activation Throughout the Heart, in Relation to a 

 Theory of P and QRS 



Direction of Excitation Wave Recorded With Bipolar 

 Electrode Combinations at the Surface 



Latencies at the Ventricular Surface 



Latencies Across the Ventricular Wall 

 General Principles Underlying Interpretation of the Electro- 

 cardiogram 



Areas of QRS and T and the Ventricular Gradient 



Amount of Cancellation of Fiber Dipoles 



Influence of Conduction Velocity Upon the QRS Complex 



Form of the QRS Complex 



General Principles Underlying Interpretation of the T Wave 

 Description of the PQRS Part 



Nomenclature 



The Normal P Wave 



The QRS Complex 



The Vector Loop 

 The RS-T Segment and Repolarization 



The Normal T Wave and the Ventricular Gradient 



The ST interval 



The QT Duration : "Electrical Systole" 

 The U Wave 



Relations Between the ECG and the Mechanical Events in the 

 Heart 



Time Relations in the Whole Heart 



Coupling of Electrical and Mechanical Events 



Variability of the ECG 



The Individual Properties of the ECG 



Changes in the Course of Age 

 Various Influences on the ECG 



Bodily Work 



Anoxia, Hypoxia, Carbon Dioxide 



Influence of Autonomic Innervation on the ECG 



Psychological Influence 



Metabolism 



Ions 



Drugs 



Hypothermia 



Acceleration 



The Fetal ECG, and the ECG in Pregnancy 

 The Theory of Normal and Abnormal Rhythms 



The Pacemaker 



Dissociation and Interference 



Extrasystoles 



Heart Rate, Tachycardias, and Paroxysms. Physiological 

 Arrhythmias 



Periods. Alternans 



The ECG of Ectopic Beats 

 Comparative Electrocardiography 



THE ELECTROCARDIOGRAM (ECG) is the rccord of a 

 superposition of electromotive forces which originate 

 during the activation process in the individual heart 

 muscle fibers. Action currents from the heart were re- 

 corded very early in the history of physiology. In 

 1855, Koelliker & Miiller (295) first demonstrated 

 what they called the negative deflection of a beating 

 frog heart. The first actual recording of a frog ECG 

 was made by A. D. Waller (505) in 1887, and that of 

 a human heart, in i88g. The era of modern electro- 

 cardiography, however, started with Einthoven (182), 

 who, by the invention of the string galvanometer, was 

 able to record small voltages of short duration. His re- 

 cording techniques have not been much improved 



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