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.