The Only EKG Book You'll Ever Need

255 Pages·2015·10.4 MB·English

by  Thaler, Malcolm S.

2015
Contents
Getting Started
Chapter 1
The Basics
Electricity and the Heart
The Cells of the Heart
Time and Voltage
P Waves, QRS Complexes, T Waves, and Some Straight Lines
Naming the Straight Lines
Summary: The Waves and Straight Lines of the EKG
Making Waves
The 12 Views of the Heart
A Word About Vectors
The Normal 12-Lead EKG
Summary: Orientation of the Waves of the Normal EKG
Coming Attractions
Chapter 2
Hypertrophy and Enlargement of the Heart
Definitions
Axis
Summary: Axis
Axis Deviation, Hypertrophy, and Enlargement
Atrial Enlargement
Summary: Atrial Enlargement
Ventricular Hypertrophy
Secondary Repolarization Abnormalities of Ventricular Hypertrophy
Summary: Ventricular Hypertrophy
Case 1
Case 2
Chapter 3
Arrhythmias
The Clinical Manifestations of Arrhythmias
Why Arrhythmias Happen
Rhythm Strips
How to Determine the Heart Rate From the EKG
The Five Basic Types of Arrhythmias
Arrhythmias of Sinus Origin
Summary: Arrhythmias of Sinus Origin
Ectopic Rhythms
Reentrant Rhythms
The Four Questions
Supraventricular Arrhythmias
Summary: Supraventricular Arrhythmias
Ventricular Arrhythmias
Summary: Ventricular Arrhythmias
Supraventricular Versus Ventricular Arrhythmias
Summary: Ventricular Tachycardia Versus PSVT With Aberrancy
Programmed Electrical Stimulation
Implantable Defibrillators
External Defibrillators
Case 3
Case 4
Case 5
Chapter 4
Conduction Blocks
What Is a Conduction Block?
AV Blocks
Summary: AV Blocks
Bundle Branch Block
Summary: Bundle Branch Block
Hemiblocks
Combining Right Bundle Branch Block and Hemiblocks
Blocks That Underachieve
The Ultimate in Playing With Blocks: Combining AV Blocks, Right Bundle Branch Block, and
Hemiblocks
Pacemakers
Case 6
Case 7
Case 8
Chapter 5
Preexcitation Syndromes
What Is Preexcitation?
Wolff–Parkinson–White Syndrome
Lown–Ganong–Levine Syndrome
Associated Arrhythmias
Summary: Preexcitation
Case 9
Chapter 6
Myocardial Ischemia and Infarction
What Is a Myocardial Infarction?
How to Diagnose a Myocardial Infarction
Summary: The EKG Changes of an Evolving Myocardial Infarction
Localizing the Infarct
Non–Q-Wave Myocardial Infarctions
Apical Ballooning Syndrome
Angina
Summary: The ST Segment in Ischemic Cardiac Disease
Limitations of the EKG in Diagnosing an Infarction
Stress Testing
Case 10
Case 11
Chapter 7
Finishing Touches
Electrolyte Disturbances
Hypothermia
Drugs
More on the QT Interval
Other Cardiac Disorders
Pulmonary Disorders
Central Nervous System Disease
Sudden Cardiac Death
The Athlete's Heart
Preparticipation Screening for Athletes
Sleep Disorders
The Preoperative Evaluation
Summary: Miscellaneous Conditions
Case 12
Case 13
Chapter 8
Putting It All Together
The 11-Step Method for Reading EKGs
Review Charts
Chapter 9
1
How Do You Get to Carnegie Hall?
Index
Getting Started
In this chapter you will learn:
1
not a thing, but don't worry. There is plenty to come. Here is your chance to turn a few
pages, take a deep breath or two, and get yourself settled and ready to roll. Relax. Pour
some tea. Begin.
On the opposite page is a normal electrocardiogram, or EKG. By the time you have finished this
book—and it won't take very much time at all—you will be able to recognize a normal EKG almost
instantly. Perhaps even more importantly, you will have learned to spot all of the common
abnormalities that can occur on an EKG, and you will be good at it!
Some people have compared learning to read EKGs with learning to read music. In both
instances, one is faced with a completely new notational system not rooted in conventional language
and full of unfamiliar shapes and symbols.
But there really is no comparison. The simple lub–dub of the heart cannot approach the subtle
complexity of a Beethoven string quartet (especially the late ones!), the multiplying tonalities and
polyrhythms of Stravinsky's Rite of Spring, or the extraordinary jazz interplay of Keith Jarrett's
Standards Trio.
There's just not that much going on.
The EKG is a tool of remarkable clinical power, remarkable both for the ease with which it can
be mastered and for the extraordinary range of situations in which it can provide helpful and even
critical information. One glance at an EKG can diagnose an evolving myocardial infarction, identify a
potentially life-threatening arrhythmia, pinpoint the chronic effects of sustained hypertension or the
acute effects of a massive pulmonary embolus, or simply provide a measure of reassurance to
someone who wants to begin an exercise program.
Remember, however, that the EKG is only a tool and, like any tool, is only as capable as its user.
Put a chisel in my hand and you are unlikely to get Michelangelo's David.
The nine chapters of this book will take you on an electrifying voyage from ignorance to
dazzling competence. You will amaze your friends (and, more importantly, yourself). The
road map you will follow looks like this:
Chapter 1: You will learn about the electrical events that generate the different
waves on the EKG, and—armed with this knowledge—you will be able to
recognize and understand the normal 12-lead EKG.
Chapter 2: You will see how simple and predictable alterations in certain waves
permit the diagnosis of enlargement and hypertrophy of the atria and ventricles.
Chapter 3: You will become familiar with the most common disturbances in
cardiac rhythm and will learn why some are life threatening while others are
merely nuisances.
Chapter 4: You will learn to identify interruptions in the normal pathways of
cardiac conduction and will be introduced to pacemakers.
Chapter 5: You will see what happens when the electrical current bypasses the
usual channels of conduction and arrives more quickly at its destination.
Chapter 6: You will learn to diagnose ischemic heart disease: myocardial
infarctions (heart attacks) and angina (pain that results when regions of the heart
are deprived of oxygen).
Chapter 7: You will see how various noncardiac phenomena can alter the EKG.
Chapter 8: You will put all your newfound knowledge together into a simple 11-
step method for reading all EKGs.
Chapter 9: A few practice strips will let you test your knowledge and revel in
your astonishing intellectual growth.
The whole process is straightforward and should not be the least bit intimidating. Intricacies of
thought and great leaps of creative logic are not required.
This is not the time for deep thinking.
1. The Basics
In this chapter you will learn:
1
how the electrical current in the heart is generated
2
how this current is propagated through the four chambers of the heart
3
that the movement of electricity through the heart produces predictable wave patterns on
the EKG
4
how the EKG machine detects and records these waves
5
that the EKG looks at the heart from 12 different perspectives, providing a remarkable
three-dimensional electrical map of the heart
6
that you are now able to recognize and understand all the lines and waves on the 12-lead
EKG.
Electricity and the Heart
Electricity, an innate biologic electricity, is what makes the heart go. The EKG is nothing more than a
recording of the heart's electrical activity, and it is through perturbations in the normal electrical
patterns that we are able to diagnose many different cardiac disorders.
All You Need to Know About Cellular Electrophysiology in Two Pages
Cardiac cells, in their resting state, are electrically polarized; that is, their insides are negatively
charged with respect to their outsides. This electrical polarity is maintained by membrane pumps that
ensure the appropriate distribution of ions (primarily potassium, sodium, chloride, and calcium)
necessary to keep the insides of these cells relatively electronegative. These ions pass into and out of
the cell through special ion channels in the cell membrane.
The most common natural cause of sudden death in young persons is a disturbance in the
electrical flow through the heart, called an arrhythmia (we will talk about this in detail in
Chapter 3). Sometimes lethal electrical disturbances happen because of an inherited
disorder of these ion channels. Fortunately, these so-called channelopathies are quite rare.
Many different genetic mutations affecting the cardiac ion channels have been identified,
and more are being discovered every year.
The resting cardiac cell maintains its electrical polarity by means of a membrane pump. This pump requires a constant supply of
energy, and the gentleman above, were he real rather than a visual metaphor, would soon be flat on his back.
Cardiac cells can lose their internal negativity in a process called depolarization.
Depolarization is the fundamental electrical event of the heart. In some cells, known as
pacemaker cells, it occurs spontaneously. In others, it is initiated by the arrival of an electrical
impulse that causes positively charged ions to cross the cell membrane.
Depolarization is propagated from cell to cell, producing a wave of depolarization that can be
transmitted across the entire heart. This wave of depolarization represents a flow of electricity, an
electrical current, that can be detected by electrodes placed on the surface of the body.
After depolarization is complete, the cardiac cells restore their resting polarity through a process
called repolarization. Repolarization is accomplished by the membrane pumps, which reverse the
flow of ions. This process can also be detected by recording electrodes.
All of the different waves that we see on an EKG are manifestations of these two processes:
depolarization and repolarization.