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EKG Plain and Simple, 4th Edition Class Notes

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EKG Plain and Simple, 4th Edition Class Notes summarizes important topics for quick revision.

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    1 1 C ardiac Anatomy and Physiology Chapter Synopsis This chapter covers basic heart structure and function, starting with a description of the heart’s layers and chambers and progressing to the cardiac cycle and a description of the phases of systole and diastole. It is meant to be very general as it is a basis for the electrocardiography to be covered in later chapters. The instructor who wants more detail may wish to refer to an anatomy or physiology text. The information in this chapter can usually be covered in one to two 75 - minute classes. Chapter Outline I. Introduction II. Layers of the Heart A. Epicardium B. Myocardium C. Endocardium III. Heart Chambers A. Right atrium B. Right ventricle C. Left atrium D. Left ventricle

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    2 IV. Heart Valves A. Semilunar valves 1. Pulmonic 2. Aortic B. Atrioventricular valves 1. Tricuspid 2. Mitral V. Great Vessels A. Superior vena cava (SVC) B. Inferior vena cava (IVC) C. Pulmonary artery D. Pulmonary veins E. Aorta VI. Blood Flow t hrough the Heart VII. The Cardiac Cycle A. Diastole 1. Rapid - filling phase 2. Diastasis 3. Atrial kick B. Systole 1. Isovolumetric contraction 2. Ventricular ejection 3. Protodiastole 4. Isovolumetric relaxation VIII. Blood Flow Through the Systemic Circulation IX. Coronary Arteries A. Left main coronary artery (L MCA ) a. Left anterior descending branch b. Circumflex branch C. Right coronary artery (RCA)

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    3 X. Heart Cells A. Contractile cells B. Conduction system cells XI. Nervous Control of the Heart A. Sympathetic nervous system B. Parasympathetic nervous system XII. Chapter 1 Notes — To Sum It All Up… XIII. Practice Quiz XIV. Putting It All Together — Critical Thinking Exercises Chapter Objectives Upon completion of this chapter, the student will be able to: • State the location of the heart and its normal size. • Name the walls and layers of the heart. • Name all the structures of the heart. • Track the flow of blood through the heart. • State the oxygen saturation of the heart’s chambers. • Describe the function and location of the heart valves. • Describe the relationship of the valves to heart sounds. • List the great vessels and the chamber into which they empty or from which they arise. • State what occurs in each phase of the cardiac cycle. • Name and describe the function of the coronary arteries. • Differentiate between the two kinds of cardiac cells. • Describe the sympathetic and parasympathetic nervous systems. • Describe the fight - or - flight and rest - and - digest resp onses. Frequently Asked Questions (FAQs) by Students • I know someone with an enlarged heart. What does that mean? Suggested answer: That means his or her heart is larger than average. This may be because of high blood pressure, other heart problems, or it could simply be normal

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    4 for them. An enlarged heart is not necessarily a problem. (As an instructor, you should always encourage students with medical concerns to see their physician. You should provide only general information. Do not diagnose unless you are a physician.) • How does the blood flow uphill from the legs to the heart? Because humans are erect beings, it seems that gravity would tend to keep the blood in the legs and feet. Suggested answer: Arteries push the blood away from the heart under pressure — the blood pressure. Veins return blood to the heart without the benefit of this pressure. Three things enable venous blood to flow uphill against gravity. First, veins have valves. That prevents the blood from backflowing. Next, the negative pressure in the thoracic cavity during the respiratory cycle essentially serves as a vacuum and “sucks” the blood uphill toward the heart. Finally, the muscles in the legs squeeze the leg veins, forcing the blood up toward the heart. • Do coronary arteries change during one’s life or are they a certain way from birth? Suggested answer: Individuals who have frequent coronary chest pain can develop collateral circulation, small tributary blood vessels that provide blood flow around a narrowed area of a major coronary artery. For most people, the coronary arteries remain the ones with which they are born. Studies are under way to understand what causes angiogenesis, the development of new blood vessels. Suggested Class Activities • To illustrate the parasympathetic nervous system’s effect on the heart rate (the heart rate falls when the glottis is closed because a closed glottis causes vagus nerve stimulation), have the students take a deep breath and then hold it while palpating their pulse. The decrease in heart rate should be obvious. If you have access to a cardiac monitor, attach a student volunteer to the monitor and record the decrease in heart rate during breath holding. Students always enjoy this, and it helps liven up what could be dry subject matter. • Have an anatomy/physiology bee. This is the equivalent of a spelling bee. Line the students up against the wall. Ask anatomy questions. Each student who answers incorrectly sits down. The last one standing is the winner.

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    5 • Hand out a blank heart diagram and have the students label the structures. • If you have access to a stethoscope, have the students listen to each others’ heart sounds. • Hand out a blank diagram of the coronary vessels and have the students label the coronary arteries and veins. • Have the students point out the coronary arteries and heart structures on a heart model if one is accessible. Critical Thinking Exercises Anatomy and physiology can be — let’s face it — pretty boring. Students can memorize the material in the chapter, but they need to understand the clinical implications of anatomic and/or physiologic heart disturbances. This focus on “here’s the situation — what does it mean physiologically for the patient?” will help them later on in the rhythms chapters. Utilize the following scenarios or make up your own and have the students explain the anatomy and/or physiology behind the situations. The suggested answers are simply a guide for the instructor. • Mrs. Breaux has developed a heart rhythm that alters her heart’s physiology — she no longer has atrial kick. Have the students explain what this means to the patient. Suggested answer: Atrial kick is the last phase of diastole — it accounts for 15 – 30% of ventricular filling. With a rhythm that does not allow atrial kick, the other phases of diastole will occur as usual, but there will be no atrial contraction/atrial kick. Therefore, the ventricles will be less full when systole begins. This can cause a drop in the amount of blood expelled by the heart (cardiac output). • Mr. Thompson has a mitral valve that is stenosed (narrowed). Have the students explain what happens to the left atrium as it struggles to pass its blood through the stenosed mitral valve. Suggested answer: Because the mitral valve is stenosed, it does not allow easy passage of blood through it. The left atrial muscle will , therefore , “bulk up” to enable it to contract more forcefully to force blood through the stenosed valve into

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    6 the left ventricle (just like the left ventricle has more muscle bulk than the right ventricle because it pumps against resistance). • Mr. Hopkins has been in an automobile accident. His arm is badly injured and he is bleeding profusely. Have the students explain what role the autonomic nervous system plays in the body’s initial response to this injury. Suggested answer: This is a classic fight - or - flight scenario. The sympathetic nervous system will trigger the adrenal gland to pour out norepinephrine, causing the heart rate and blood pressure to increase. With a large blood loss, the cardiac output will drop, triggering the heart to speed up to circulate th e remaining blood around faster. Crossword Puzzle The crossword puzzle that follows can be used as a take - home or in - class test, or just given out as practice.

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    9 2 Electrophysiology Chapter Synopsis This chapter covers the electrical events that control the cardiac cycle and introduces the EKG waves and complexes and the conduction system. Many practice examples enhance learning. Two 75 - minute classes should be enough to cover this chapter. Chapter Outline I. Introduction II. Depolarization and Repolarization III. The Action Potential A. Phase 4 B. Phase 0 C. Phases 1 and 2 D. Phase 3 IV. Refractory Periods A. Absolute B. Relative C. Supernormal period V. EKG Waves and Complexes A. P wave B. T a wave C. QRS complex D. T wave E. U wave VI. Waves and Complexes Identification Practice VII. QRS Nomenclature

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    10 A. Q wave B. R wave C. S complex D. QS wave VIII. QRS Nomenclature Practice IX. Cardiac Conduction System A. Conduction Pathway X. Cardiac Cells A. Automaticity B. Conductivity C. Excitability D. Contractility XI. Inherent (Escape) Rates of the Pacemaker Cells XI I . Conduction Variations XIII. EKG Paper XIV. Intervals A. PR interval B. QRS interval C. QT interval XV. Intervals Practice XVI. Chapter 2 Notes — To Sum It All Up… XVII. Practice Quiz XVIII. Putting It All Together — Critical Thinking Exercises Chapter Objectives Upon completion of this chapter, the student will be able to: • Define the terms polarized, depolarization, and repolarization and relate them to contraction and relaxation. • Describe and label the phases of the action potential. • Define transmembrane potential. • Draw and explain the P wave, QRS complex, T wave, and U wave.

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    11 • Explain where the PR and ST segments are located. • Define the absolute and relative refractory periods and the implications of each. • Be able to label, on a rhythm strip, all the waves and complexes. • Explain the delineations of EKG paper. • On a rhythm strip, determine if the PR, QRS, and QT intervals are normal or abnormal. • Name the waves in a variety of QRS complexes. • Define pacemaker. • List the different pacemakers of the heart and their inherent rates. • Track the cardiac impulse from the sinus node through the conduction system. • Define the four characteristics of cardiac cells. • Describe the difference between escape and usurpation. • Define arrhythmia. • Tell what happens: When the sinus node fails . When the sinus node and atria both fail . When the sinus node, atria, and AV node all fail . Frequently Asked Questions (FAQs) by Students • How can the T a wave be happening at the same time as the QRS complex? Suggested answer: The T a wave and the QRS complex represent events happening simultaneously in different chambers of the heart. These events do not cancel each other out — they occur simultaneously. Because ventricular depolarization generates a large amount of electrical current, it “ swallows up ” the T a wave that occurs at the same time. • How can a rhythm have no P wave? Suggested answer: Some rhythms originate in different parts of the conduction system and do not depolarize the atria, thus no P wave is written. There are many rhythms that have no P waves.

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    12 • Why is a purely negative QRS complex called a QS wave? Why not just Q or just S instead of both? Suggested answer: A Q wave is a negative wave that precedes an R wave. An S wave is a negative wave that follows an R wave (just as in the alphabet). If there is no R wave to go by, the negative wave can’t really be called a Q or an S, so a compromise is made and it is called QS. • What happens if all the pacemakers fail? Suggested answer: If all the pacemakers fail, there are no waves or complexes at all on the EKG printout. There is only a flat line to indicate the complete lack of electrical current in the heart. The patient in this case has no pulse, is not breathing, and is clinically dead. • Can a pacemaker stop for a while and then “wake up” again? Suggested answer: Absolutely. In fact, that is a frequent occurrence. Hopefully, one of the other pacemakers will keep things going until the faster pacemaker resumes control. • Do patients feel it when a different pacemaker takes over? Suggested answer: Patients do not feel the change in pacemakers per se. What they feel, if anything, is a change in heart rate, either faster or slower. Some patients report feeling palpitations when a lower pacemaker usurps the predominant pacemaker at a very rapid heart rate. And some patients feel a big thump when there has been a long pause and an escape beat kicks in. This change in heart rate, either faster or slower, can cause symptoms of low cardiac output. Suggested Class Activities • Hand out practice sheets with different QRS configurations and have the students name the waves. • Have students get into small groups and practice labeling the waves and complexes of various rhythm strips. The students who are catching on more quickly can help the slower ones.

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    13 • Have an electrophysiology bee. Line students up against the wall. Ask each student a question about electrophysiology. Students answering incorrectly sit down. The last one standing is the winner. • If you have access to a rhythm simulator, show the students a sinus rhythm with a rate between 60 and 100. Then show a junctional rhythm with a rate between 40 and 60. Finally, switch to a ventricular rhythm with a rate between 20 and 40. This is a good way for the students to see what the slower heart rates caused by each lower pacemaker look like. • Have the students label a diagram of the conduction system. • Have the students track the heart’s current from the sinus node through the conduction system to the ventricle. • Have four students stand in front of the class. Assign each one to be a pacemaker of the heart. Have a small ball on the table in front of them. Ask them to demonstrate what happens in sinus rhythm. The sinus student should pick up a ball and hand it to the atrium, who hands it to the AV node/junction, who hands it to the ventricle. The student representing the ventricle jumps up and down to indicate depolarization. • Now ask them to demonstrate what happens when the sinus node fails. Typically, the next pacemaker in line to replace the failing sinus node is the AV junction. The sinus node and atrium students should do nothing. The AV node/junction student should pick up the ball and hand it to the ventricle, who then jumps up and down to represent depolarization. • You can make up more scenarios like this. It is undeniably corny, but it gets the students participating and makes them laugh (especially the poor student who represents the ventricle by jumping up and down). Critical Thinking Exercises Utilize the following scenarios or make up your own to get the students thinking about electrophysiology. • Mr. Miller’s heart monitor alarmed, showing his rhythm was a flat line. Have the students explain what is happening — or not happening — electrically and mechanically. Will he have a pulse?

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    14 Suggested answer: Mr. Miller’s flat line tells us that nothing is happening electrically in his heart. There is no depolarization or repolarization. And if there is no depol/repol, there can be no mechanical response. The heart can’t pump if it has not been depolarized first. There will be no pulse. • Mrs. Tucker has a rhythm that has no P waves. Have the students explain what this means in terms of atrial depol/repol and the phases of diastole. Suggested answer: If there is no P wave, there is no atrial depolarization and therefore no atrial contraction/atrial kick. This does not mean there is no blood flow from atrium to ventricle . Blood flow from atrium to ventricle will still occur passively as usual in the first phases of diastole. There will just not be the atrial kick to squeeze the last 15 – 30% of the blood into the ventricle. • Mr. Tart has a PR interval that has changed from 0.12 seconds to 0.24 sec ond s after starting a new medication. Have the students tell what this PR interval change means physiologically. Are the intervals normal or abnormal? Suggested answer: The increased PR interval means it takes the impulse longer to reach the ventricle than before the medication was started. The new PR interval is abnormally prolonged. Crossword Puzzle The crossword puzzle below can be used as a take - home or in - class test, or just given out as practice.

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    17 3 Lead Morphology and Placement Chapter Synopsis This chapter introduces leads and lead placement and describes what each lead of a normal 12 - lead EKG should look like. With modern monitoring systems displaying multiple leads during continuous monitoring, it is imperative that the student know the normal QRS morphology of each lead. The information in this chapter can be covered in one or two 75 - minute classes. Chapter Outline I. Introduction II. Lead Types I II. Bipolar Leads I V . Augmented Leads V. Precordial (Chest) Leads V I . Continuous Monitoring VII. The Most Commonly Used Leads for Continuous Monitoring VI II . Electrocardiographic Truths IX . Normal QRS Deflection s X. Chapter 3 Notes — To Sum It All Up… X I . Practice Quiz XI I . Putting It All Together — Critical Thinking Exercises Chapter Objectives Upon completion of this chapter, the student will be able to:

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    18 • Define electrode. • Name the bipolar leads and the limbs that comprise them. • Name the unipolar augmented leads. • Explain what augmentation does to the EKG. • Explain Einthoven’s law. • Draw and label Einthoven’s triangle. • Name the leads comprising the hexiaxial diagram. • Describe the location of the precordial leads. • Name the two leads most commonly used for continuous monitoring in the hospital. • Explain the electrocardiographic truths. • Describe the normal QRS complex deflections in each of the 12 leads on an EKG. Frequently Asked Questions (FAQs) by Students • If the morphology of a lead on the EKG is abnormal, what does that mean? Suggested answer: If the QRS morphology is abnormal, it could imply a defect in impulse transmission through the bundle branches, it could imply an MI, or it might indicate a normal variant. In addition, it could simply mean the leads were put on incorrectly (arm leads may have been reversed). • Why is the QRS in lead I supposed to be positive? The normal impulse is traveling toward the foot, not toward the arm. Shouldn’t the QRS be negative? Suggested answer: The impulse does not have to be traveling directly toward an electrode in order for the lead to write a positive deflection. The impulse merely has to be traveling in the same direction in which the positive pole of the lead is located. In other words, any limb lead whose positive pole is on the left side of the body should have a positive QRS complex, because the normal impulse travels right to left. That’s why all the frontal leads except AVR have a positive deflection. Suggested Class Activities • Hand out practice EKGs and have the students evaluate the QRS morphology.

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    19 • Use a rhythm simulator to show rhythms and ask the students if the QRS complexes are the correct morphology. • If you have access to a manikin or skeleton, have the students practice putting on the precordial leads. • Have the students practice putting precordial leads on each other. • Using a student volunteer, or a manikin or skeleton, place precordial leads in incorrect locations. Have the students examine the lead placement, tell where the error is, and then correct it. Critical Thinking Exercises Utilize these scenarios or make up your own. • Mr. Thornton has a heart rhythm that originates in the left ventricle. Have the students tell how the frontal lead morphology should look and why. Suggested answer: Because Mr. Thornton’s current starts in the left ventricle, it will head upward and to the right to depolarize the entire heart. Thus , the morphology will be as follows: Ld I — neg, Ld II — neg, Ld III — neg, aVR — pos, aVL — neg, aVF — neg. AVR will be the only positive lead because it is the only lead in which the positive pole is on the right arm where the current is traveling. • Mrs. Smith has had her left leg amputated just below the hip joint. There is not enough stump to put an electrode on. Where should her left leg electrode be placed? Suggested answer: Put the electrode on the abdomen just above where the leg would be. Crossword Puzzle The crossword puzzle that follows can be used as a take - home or in - class test, or just given out as practice.

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    22 4 Technical Aspects of the EKG Chapter Synopsis This chapter describes the function of the EKG machine and discusses some of its control features. It also discusses electrical safety and the different kinds of artifact that can impact the readability of the tracing. Troubleshooting artifact is covered, along with practice examples. Telemetry monitoring is discussed. Once armed with this knowledge, the class ideally will be able to practice performing EKGs. This chapter can be covered in one 75 - minute class. Chapter Outline I. Introduction II. Control Features A. Chart speed B. Gain C. Frequency response III. Electrical Safety A. Macroshock B. Microshock IV. Artifact A. Somatic tremors B. Baseline sway C. 60 - cycle interference D. Broken recording

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    23 V. Troubleshooting VI. Artifact Troubleshooting Practice VII . Artifact Masquerading as Rhythms A. Artifact masquerading as asystole B. “Toothbrush tachycardia” C. CPR artifact D. Defibrillation/cardioversion artifact VIII . Artifact in T hree L eads M onitored S imultaneously I X. Is It Real or Is It A rtifact? X. Real or Artifact: How to Tell the Difference XI. Chapter 4 Notes — To Sum It All Up… XII. Practice Quiz XI II . Putting It All Together — Critical Thinking Exercises Chapter Objectives Upon completion of this chapter, the student will be able to: • Identify the control features of an EKG machine and describe the functions of each. • Describe what a digital converter does. • Differentiate between macroshock and microshock. • Describe and identify on a rhythm strip the different kinds of artifact. • Correctly tell how to troubleshoot artifact. • Tell how to differentiate between artifact and a real rhythm. • Correctly identify artifact versus rhythm. Frequently Asked Questions (FAQs) by Students • How can you tell if the EKG rhythm is real or if it’s artifact? Suggested answer: Some artifact, such as baseline sway, is very obvious and easily remedied. Other artifact is less obvious. Some patients, for example, have fine muscle tremors that can make the rhythm look completely abnormal. It helps to compare the present EKG to previous ones. If there is a big difference that does not

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    24 seem to jive with the patient’s clinical status, check your patient. If he/she has symptoms of decreased cardiac output, the rhythm is probably real. Artifact does not produce symptoms. If there are no symptoms, it would be wise to redo the EKG, just in case. Most of the time, though, the typical problems such as reversing the arm leads are easily detected, because the QRS deflections will be backward from the normal (and because modern EKG machines will indicate if leads are reversed) . Remember the normal QRS deflections in each lead. If the QRS deflections have changed from the last EKG, check your lead placement. If in doubt, redo the EKG. Suggested Class Activities • Give the students rhythm strips along with a scenario and have them determine whether the rhythm is real or artifact. For example, show a strip of what looks like v - tach and tell the class the patient is brushing her teeth and is awake and feeling fine. • Have the class act out various scenarios, using a rhythm simulator to show the rhythm in question. Have the rest of the class decide whether the rhythm is real or artifact. • If there is a clinical component to the class, have the students collect strips of artifact in a rhythms scrapbook. • Divide the class into groups of five or six. Ask questions about artifact masquerading as rhythms. Show rhythm strips. Each group must reach a consensus on the answer, and one spokesperson must give the group’s answer. Each correct answer is worth 10 points. The group with the highest score wins. • Have the class practice doing a 12 - lead EKG on student volunteers. Have the volunteer then move his/her arms wildly, then in a tremulous manner to create artifact so the students can see what kinds of movements cause artifact and in which leads the artifact is most noticeable. • Practice doing an EKG with the arm leads reversed, so the students see how it looks. • Ask the students what they would do if an EKG machine they were planning to use had a broken grounding prong.

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    25 Critical Thinking Exercises Utilize the following scenarios or make up your own. • Mr. Corwin had a heart attack and is recovering nicely. He is up brushing his teeth when a nurse rushes in and asks him how he’s feeling. His heart rhythm looks dangerous. Mr. Corwin admits he feels lousy — dizzy, with mild chest pain and a little shortness of breath. Ask the students whether they think the “dangerous rhythm” is artifact or real — or could it be both? Suggested answer: The rhythm could be real — Mr. Corwin is showing symptoms that could correlate with his rhythm — or it could be that he indeed had “toothbrush tachycardia” and no rhythm problem at all. The symptoms he’s having could be completely unrelated to the rhythm. The presence of artifact does not preclude the possibility that there could be additional problems. • Mrs. Trahan has flat - line on the monitor. The nurse does not rush to the room because the patient has had a lot of artifact previously and the nurse thinks this is once again artifact. She arrives in the room in due time to find the patient on the floor in cardiac arrest. Ask the students what they think about the nurse’s assumption that this was artifact? Suggested answer: The students should realize that each time is different. Always check the patient immediately. Crossword Puzzle The crossword puzzle that follows can be used as a take - home or in - class test, or just given out as practice.

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    28 5 Calculating Heart Rate Chapter Synopsis This chapter covers the different methods of heart rate calculation based on the type of rhythm regularity. Many practice examples help the student learn both regularity and heart rate calculation. This material can be covered in two 75 - minute classes, offering plenty of time for practice. Chapter Outline I. Introduction II. Methods for Calculating Heart Rate A. The 6 - second strip method B. The memory method C. The little block method III. Regularity - Based Heart Rate Calculation IV. Regularity Types A. Regular B. Regular but interrupted C. Irregular V. Practice Strips: Regularity of Rhythms VI. Kind of Heart Rate to Calculate for Different Types of Regularity A. For regular rhythms B. For irregular rhythms C. For rhythms that are regular but interrupted by premature beats D. For rhythms that are regular but interrupted by pauses VII. Practice Strips: Calculating Heart Rate VIII. Chapter 5 Notes — To Sum It All Up…

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