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Bradycardias, Tachycardias and Other Heart Rhythm

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Bradycardias, Tachycardias and Other Heart Rhythm BRADYCARDIAS, TACHYCARDIAS AND OTHER HEART RHYTHM DISTURBANCES BASIC ELECTROCARDIOGRAPHY JASSIN M. JOURIA, MD Dr. Jassin M. Jouria is a practicing Emergency Medicine physician, professor of academic medicine, and medical author. He graduated from Ross University School of Medicine and has completed his clinical clerkship training in various teaching hospitals throughout New York, including King’s County Hospital Center and Brookdale Medical Center, among others. Dr. Jouria has passed all USMLE medical board exams, and has served as a test prep tutor and instructor for Kaplan. He has developed several medical courses and curricula for a variety of educational institutions. Dr. Jouria has also served on multiple levels in the academic field including faculty member and Department Chair. Dr. Jouria continues to serve as a Subject Matter Expert for several continuing education organizations covering multiple basic medical sciences. He has also developed several continuing medical education courses covering various topics in clinical medicine. Recently, Dr. Jouria has been contracted by the University of Miami/Jackson Memorial Hospital’s Department of Surgery to develop an e-module training series for trauma patient management. Dr. Jouria is currently authoring an academic textbook on Human Anatomy & Physiology. ABSTRACT Electrocardiograms are valuable tests for evaluating heart health and to diagnose cardiac issues. But the test is only as good as the skill of the clinician performing it. Medical clinicians must commit to learning and updating their electrocardiogram procedure and interpretation skills to arrive at a correct diagnosis, and these skills start with an understanding of the basic function of the electrocardiogram. Being able to identify normal readings on an electrocardiogram rhythm strip is the first step to recognizing cardiac issues, and possibly saving lives. 1 nursece4less.com nursece4less.com nursece4less.com nursece4less.com Policy Statement This activity has been planned and implemented in accordance with the policies of NurseCe4Less.com and the continuing nursing education requirements of the American Nurses Credentialing Center's Commission on Accreditation for registered nurses. It is the policy of NurseCe4Less.com to ensure objectivity, transparency, and best practice in clinical education for all continuing nursing education (CNE) activities. Continuing Education Credit Designation This educational activity is credited for 3.5 hours. Nurses may only claim credit commensurate with the credit awarded for completion of this course activity. Pharmacology content is 0.5 hours (30 minutes). Statement of Learning Need Health clinicians in general practice and cardiology need to be able to understand the function and information generated by an electrocardiogram. The correct diagnosis and proper treatment of a cardiac condition is dependent on competent and accurate interpretation of diagnostic tests, which includes the electrocardiogram in both inpatient and outpatient settings. 2 nursece4less.com nursece4less.com nursece4less.com nursece4less.com Course Purpose To provide health clinicians with basic knowledge about the purpose, function and diagnostic data of an electrocardiogram. Target Audience Advanced Practice Registered Nurses and Registered Nurses (Interdisciplinary Health Team Members, including Vocational Nurses and Medical Assistants may obtain a Certificate of Completion) Course Author & Planning Team Conflict of Interest Disclosures Jassin M. Jouria, MD, William S. Cook, PhD, Douglas Lawrence, MA Susan DePasquale, MSN, FPMHNP-BC – all have no disclosures Acknowledgement of Commercial Support There is no commercial support for this course. Please take time to complete a self-assessment of knowledge, on page 4, sample questions before reading the article. Opportunity to complete a self-assessment of knowledge learned will be provided at the end of the course. 3 nursece4less.com nursece4less.com nursece4less.com nursece4less.com 1. The P wave is a summation wave that is generated by the depolarization front as it transits the a. sinoatrial node. b. ventricles. c. bundle of His. d. atria. 2. True or False: Normally, the right atrium depolarizes earlier than the left atrium since the depolarization wave originates in the sinoatrial node. a. True b. False 3. An ECG reading showing a P wave with increased amplitude can be an indication of a. hyperkalemia. b. hypokalemia. c. Wolff–Parkinson–White (WPW) syndrome. d. hypotrophy. 4. ______________________ are known as P mitrale and indicate left-atrial abnormality, such as left-atrial dilation or hypertrophy. a. Bifid P waves b. P waves with increased amplitude c. P wave with a flat baseline d. P waves that are not clearly delineated 5. ______________ is an ECG recording that was not made by the electrical activity of the heart. a. An ECG artifact b. An ectopic c. A bifid P wave d. An ECG variant 4 nursece4less.com nursece4less.com nursece4less.com nursece4less.com Introduction An electrocardiogram indicates heart activity by recording atrial and ventricular activity. It generates waveforms that become recorded on an electrocardiogram report. Variations in the normal progression of an electrocardiogram, waveform intervals or amplitude, can be a sign that a patient may have a certain medical condition. It is important for a clinician to understand what medical condition is associated with a specific change in the electrical activity of the heart. Examination of the electrocardiogram is key to appropriate diagnosis in addition to a physical examination and accurate history taking. The goal is to determine whether heart rhythm abnormalities exist in the electrocardiogram report and to correlate those with any reported symptoms. Atrial Depolarization And Repolarization The electrocardiogram measures electrical impulses while they travel through the heart, using ECG patches with wires attached to the skin to measure the impulses, the impulses display on a monitor or print on paper as waves of electrical activity. The electrocardiogram measures the electrical impulses as five distinct waves. These waves are called P, Q, R, S, and T. The Q through T waves show electrical activity in the lower chambers (ventricles) of the heart. When considering the P waves and their presence, frequency, relationship to the QRS complex, appearance, and conformity, the P wave in an electrocardiogram (ECG) represents atrial depolarization that results in atrial contraction. The P wave is a summation wave that is generated by the depolarization front as it transits the atria. Normally, the right atrium depolarizes earlier than the left atrium since the depolarization wave originates in the sinoatrial node, in the high right atrium and then through the left atrium. 5 nursece4less.com nursece4less.com nursece4less.com nursece4less.com The depolarization front is carried through the atria along semi-specialized conduction pathways including Bachmann's bundle. This results in uniform shaped waves. Depolarization that originates elsewhere in the atria as with atrial ectopy results in a P wave with a different morphology compared to normal. A P wave with increased amplitude can be an indication of hypokalemia. It can also be an indication of atrial enlargement. A P wave with decreased amplitude can be an indication of hyperkalemia. Bifid P waves are known as P mitrale and indicate left-atrial abnormality, such as left-atrial dilation or hypertrophy.19 In a situation where at least three different shaped P wave are on a given ECG lead tracing, this can imply that even if one arises from the SA node, at least two can arise elsewhere. This could be evidence of multiple ectopic foci called multifocal or multiform atrial rhythm if the rate is equal to or less than 100. It is multifocal atrial tachycardia if the rate is over 100. This can be common in exacerbations of chronic obstructive lung disease. If the baseline has a totally irregular form this could suggest fibrillatory waves of atrial fibrillation. It could also suggest possible ECG artifact, which is an ECG recording that was not made by the electrical activity of the heart. A baseline with a saw tooth shape suggests the flutter waves of atrial flutter. With these two rhythms and a fast ventricular rate, it is easy to misinterpret the fibrillatory or flutter waves as P waves. The absence of a P wave with a flat baseline could indicate fine atrial fibrillation or sinoatrial arrest with a secondary escape rhythm. If P waves are not clearly delineated in the surface ECG, another lead can be used to better visualize the P waves. Atrial repolarization occurs at a mean of 320 milliseconds (ms) after the end of a P wave. It has a duration of 2-3 times that of the P wave. The polarity is 6 nursece4less.com nursece4less.com nursece4less.com nursece4less.com always opposite to that of the P wave. It is represented on a surface ECG as what is called a Ta wave. In a normal ECG, atrial and ventricular depolarization and repolarization appear on an ECG as a series of waves. The P wave is followed by the QRS complex and the T wave. The first deflection is the P wave associated with right and left atrial depolarization. The first positive deflection in the complex is called an R wave. The normal ECG patterns are explained more specifically below. PR Interval In electrocardiography, the PR interval is the period that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization). It is measured in milliseconds. This interval is sometimes termed the PQ interval. Variations in the PR interval can mean an association with certain medical conditions. A long PR interval is considered to be over 200 ms. This can indicate a first degree heart block. Prolongation can be associated with the condition of hypokalemia, acute rheumatic fever, or carditis associated with Lyme disease. A short PR interval is considered to be less than 120 ms. It can be associated with Wolff–Parkinson–White (WPW) syndrome, Lown–Ganong– Levine syndrome, or junctional rhythms. A variable PR interval could mean another type of heart block.
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