Lecture 4: Junctional Dysrhythmias PDF

9/18/2024 LESSON 04 READINGS NUR-5389 LESSON 04 Dr. Debra R. Hanna, PhD, RN, ACNS-BC READ: Woods/Ehrat, Section 2, Ch 5, pp. 90-...

9/18/2024 LESSON 04 READINGS NUR-5389 LESSON 04 Dr. Debra R. Hanna, PhD, RN, ACNS-BC READ: Woods/Ehrat, Section 2, Ch 5, pp. 90-102, Junctional Professor of Nursing, Coordinator Clinical Nurse Specialist program Dysrhythmias READ: Zimmerman, Ch 17, Ch 18 Lecture 4: JUNCTIONAL DYSRHYTHMIAS 1 2 LESSON 04 OBJECTIVES The ripple effect... Imagine what a lake looks like once a rock is thrown in Explain how junctional tissue acts as an alternative cardiac pacemaker when the sinus node fails The ripples grow from the point where the rock enters the water As the ripples expand, the stillness of the lake is interrupted Identify junctional rhythms (aka: junctional escape rhythms) Identify premature junctional contractions (PJCs) Identify junctional tachycardia 3 4 When SA node impulses are generated... SA node generates impulses The impulses ripple to the left atrium. Then the impulses are transmitted through the AV node to the ventricles. The AV node does not generate any impulses 5 6 1  9/18/2024 When SA node impulses are generated... When SA node impulses are generated... With impulses generated from the SA node in the top of the right The impulses are transmitted through the AV node to the ventricles. atrium, there is a sense of top-down spread. The AV node does not generate any impulses The p waves created by the SA node impulse are rounded, upright, A-V junctional tissue around the AV node can act as a secondary and < 0.12 seconds long pacemaker if the SA node fails. Cardiac events that start with the SA node are predictable and sequential 7 8 What is junctional tissue? The normal path for cardiac impulses The Atrioventricular (AV) junctional tissue is located between And when the SA node impulse is generated, atrial tissue the bottom of the atria and the top of the ventricles depolarizes, AV junctional tissue can be excitable, so if the SA node fails, the Impulses from the SA node usually spread through intranodal AV junctional tissue becomes the back-up secondary pathways to the A-V node which is at the bottom of the right atrium pacemaker SA node impulses are transmitted via the AV node to the Bundle of His and Bundle Branches Then impulses are transmitted to the ventricular muscle walls via the Purkinje fiber ends When impulses reach the Purkinje fiber ends in ventricular muscle walls, ventricles depolarize and contract 9 10 If the SA node fails... If the SA node fails to generate an impulse, AV junctional tissue can generate impulses Remember, the fastest pacemaker always takes control If AV junctional tissue generates an impulse, the ripple-effect of the conducted impulse will ripple side-to-side and down, but it can also ripple up toward the SA node The p wave’s appearance on an EKG strip shows where the impulse was generated The specialized conduction system allows the efficient A junctional escape rhythm can have an inverted p wave, or a p wave transmission of electrical impulses throughout the heart muscle. that appears immediately after the QRS complex, or a p wave buried Red circle shows where the junctional tissue is. inside the QRS complex so that it looks like there is no p wave at all Citation: Chapter 2 Functional Anatomy and Physiology, Zimmerman FH. ECG Core Curriculum; 2023. Available at: https://accessmedicine.mhmedical.com/content.aspx?bookid=3339&sectionid=277533110 Accessed: May 12, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved 11 12 2  9/18/2024 Junctional escape rhythms When the p wave is missing, inverted (upside down), or occurs after the QRS, that strange looking, weirdly placed p wave signifies that the sinus node has failed, and the patient now has a junctional escape rhythm If this occurs for one beat only, that would be a junctional escape Sinus pause with AV junctional escape complex. Slowing of the beat normal sinus depolarization allows a subsidiary pacemaker to If it occurs as a new rhythm, that is a junctional escape rhythm emerge from the AV junction. If it is a new-onset, but persistent rhythm, this is a significant change that needs attention Citation: Chapter 15 Complex Cornucopia, Zimmerman FH. ECG Core Curriculum; 2023. Available at: https://accessmedicine.mhmedical.com/content.aspx?bookid=3339&sectionid=277534169 Accessed: July 10, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved 13 14 Frequent cause of junctional escape Why else would the SA node fail? Myocardial infarction – infarcted tissue is dead tissue & If the patient is on Digoxin, check the patient’s Dig level dead tissue cannot transmit any impulse If the Digoxin level is too high, Digoxin toxicity could suppress the Drugs: Beta-blockers, calcium channel blockers, digoxin, anti-arrhythmic meds, acetylcholinesterase inhibitors SA node which permits the AV junctional tissue to become the secondary pacemaker Ischemia Hypoxia Toxic levels of Digoxin increase the excitability of AV junctional Vagal Stimulation tissue and suppress SA node automaticity Degeneration of SA node cells – (aka - Sick Sinus If the Dig level is too high, hold Digoxin until the level reduces to Syndrome) normal and the junctional escape will resolve Hypothyroidism Hypothermia [keep this in mind if the patient is on hypothermia treatment] 15 16 Cardiac Automaticity - review Cardiac Health, Heart Rate, Blood Pressure Automaticity is a property unique to cardiac cells SA node is the primary and fastest pacemaker. SA node If the SA node (sinus node) fails to generate an impulse, generates impulses at a rate of 60-100 beats/minute the heart has backup pacemakers. SA node can also generate normal-looking beats more People can still have a heartbeat with other natural slowly (sinus brady) or more quickly (sinus tach) pacemakers, but the heartrate and EKG tracing will have People who are very healthy, such as non-smoking joggers, different qualities because the ripple effect of the impulses have healthy myocardial tissue, lungs, and vascular systems. can spread in slightly different directions They usually have low blood pressure, slow heart rate, and The other cardiac pacemakers are AV Junctional tissue, slow respiratory rate because their body at rest does not Bundle of His, Bundle branches & Purkinje fiber endpoints have a high myocardial oxygen demand. Healthy hearts are highly efficient. 17 18 3  9/18/2024 Cardiac Health, Heart Rate, Blood Pressure Secondary pacemakers If a healthy person gets a fever, as their body temperature If the SA node fails to generate any impulses, the next fastest pacemaker rises, their myocardial oxygen demand increases is in the AV junctional tissue. Their heart will beat faster to keep up with the increased The AV node has no true pacemaker fibers to initiate its own impulses need for oxygen AV Junctional tissue can generate impulses @ 40-60 beats/minute If the healthy person with a fever who normally has sinus If AV junctional tissue fails, the next backup pacemaker is the Bundle of His. bradycardia now has an increased myocardial oxygen demand, their heart rate can increase to the point of Bundle of His can generate impulses @ 40 beats/minute. becoming tachycardic (greater than 100 beats/minute) If the Bundle of His fails, the last natural pacemaker beyond the bundle branches are in the endpoints of Purkinje fibers in the ventricle walls. People with healthy hearts can have normal looking EKG Purkinje fibers can generate impulses at 20 beats/minute. This is not a fast complexes (normal looking PQRST waveforms), but the enough heart rate to provide sufficient cardiac output, or sufficient complexes can be either far apart (bradycardic) or close oxygenation to the patient’s heart & other organs. together (tachycardic) Consider a temporary pacemaker 19 20 The junction’s automaticity? A-V junctional tissue has the property of automaticity. Junctional tissue lies between the atria and the ventricles Junctional tissue can generate impulses at about 40-60 beats per minute If the SA node (sinus node) fails, the AV node or the junctional tissue would become the fastest pacemaker. A patient with severe sinus bradycardia can have a heart rate so low that the junctional tissue might take over the pacemaker function. The specialized conduction system allows the efficient transmission of electrical impulses throughout the heart muscle. Junctional tissue with the ability to generate 40-60 impulses/minute Red circle shows where the junctional tissue is. could become the fastest pacemaker. Citation: Chapter 2 Functional Anatomy and Physiology, Zimmerman FH. ECG Core Curriculum; 2023. Available at: https://accessmedicine.mhmedical.com/content.aspx?bookid=3339&sectionid=277533110 Accessed: May 12, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved 21 22 What does a junctional rhythm look like Junctional rhythm is regular Heart rate is between 40-60 beats/minute One identifying characteristic of a Junctional rhythm is that the p wave is either not visible, or is upside down (inverted), or is misplaced (after the QRS) Junctional premature complexes. The inverted, retrograde P´ The missing or inverted p wave can occur before, during, or after the wave may be present: before (a), hidden within (b), or after the QRS complex QRS complex (c). In this example, the retrograde impulse conducts to the atrium but fails to depolarize the SA node; Why would the junction’s p wave be inverted? therefore, the post-ectopic pause is fully compensatory. Citation: Chapter 15 Complex Cornucopia, Zimmerman FH. ECG Core Curriculum; 2023. Available at: https://accessmedicine.mhmedical.com/content.aspx?bookid=3339&sectionid=277534169 Accessed: July 10, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved 23 24 4  9/18/2024 Sinus pause with AV junctional escape complex. Slowing of the normal sinus depolarization allows a subsidiary pacemaker to Sinus pause with ventricular escape complex. One would emerge from the AV junction. expect the AV junction would emerge as the next subsidiary pacemaker; therefore, the presence of a ventricular escape complex implies significant disease in the AV junction. Citation: Chapter 15 Complex Cornucopia, Zimmerman FH. ECG Core Curriculum; 2023. Available at: Citation: Chapter 15 Complex Cornucopia, Zimmerman FH. ECG Core Curriculum; 2023. Available at: https://accessmedicine.mhmedical.com/content.aspx?bookid=3339&sectionid=277534169 Accessed: July 10, 2024 https://accessmedicine.mhmedical.com/content.aspx?bookid=3339&sectionid=277534169 Accessed: July 10, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved Copyright © 2024 McGraw-Hill Education. All rights reserved 25 26 The p wave in sinus bradycardia When the sinus node generates impulses slower than 60 beats/minute, that rhythm is called sinus bradycardia ONLY IF everything else about the PQRST waves is normal. For sinus bradycardia, the p wave is small, upright, rounded and comes before each QRS complex. Sinus bradycardia is a heartrate less than 60 beats/minute. The p wave is < 0.12 seconds long, and the whole p-r interval is Sinus pause with an atrial escape complex. Note the slightly different P´ wave morphology with a P´R interval remaining < 0.20 seconds, immediately before the QRS complex and a normal within the normal range. QRS complex is < 0.12 seconds long. Citation: Chapter 15 Complex Cornucopia, Zimmerman FH. ECG Core Curriculum; 2023. Available at: https://accessmedicine.mhmedical.com/content.aspx?bookid=3339&sectionid=277534169 Accessed: July 10, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved 27 28 Why is the p wave in sinus bradycardia upright? NOTE: keep Lead II for live monitoring In normal sinus rhythm, the p wave is upright because the waveforms are generated from the top of the atria and are being recorded on EKG paper as the impulses occur Some EKG leads show opposite directions for some EKG strips for live EKGs are usually in Lead II, so the p waveforms wave is positive, which means “above the isoelectric line” If the p wave is suddenly upside down, this is serious Later lessons in the course will address the many information and must be told to the MD/NP/PA angles used to look at a normal or abnormal EKG (Lead I, Lead II, Lead III; AVR, AVF, v1, v2, v3, v4, v5, v6) Do not switch to another lead just to keep the p wave For this portion of the course, all the info is about live upright since that will jeopardize the patient’s care and EKG monitoring in Lead II so that you can learn basic treatment ideas first 29 30 5  9/18/2024 The p wave in sinus bradycardia is upright Why is the p wave inverted in a junctional rhythm? With normal sinus rhythm there is a steady movement forward in In a junctional rhythm, the p wave is inverted because the waveforms are being generated below the SA node time and on EKG paper to show depolarization (the upright rounded p wave) and repolarization (the flat isoelectric line after Impulses are recorded on EKG paper in real time from the angle called Lead II the normal p wave) Live EKG monitoring (telemetry) is usually shown in Lead II In sinus bradycardia, the heart rate might be slower because the How lead placement affects what is recorded on the EKG strip is patient is super-healthy (an athlete/jogger/walker), but there are later in this course, but for now, keep in mind that the lower down also illness-related reasons for sinus bradycardia. in the heart that the impulse is generated affects how the p wave looks Sinus bradycardia is a normally conducted heartbeat at a much slower rate. The rhythm is regular and the impulse travels from When impulses come from AV junctional tissue in Lead II, the p wave is upside down, inverted, or it can appear after the QRS the SA node to the rest of the heart in the normal way complex, or it can be buried inside the QRS, so it is not visible If Sinus bradycardia goes too low, will the AV junctional tissue NOTE: a missing p wave is a strong clue to a junctional rhythm. It take over? signifies that the SA node is not firing & that the backup pacemaker took over 31 32 Escape Rhythms Premature Junctional Contraction (PJC) All escape rhythms are evidence that the higher pacemaker is If the EKG shows a single junctional ectopic beat, that would be failing since the lower pacemaker takes over only as a called a premature junctional contraction (PJC) secondary or back-up pacemaker It would occur during NSR, but suddenly there would be either a Escape rhythms are like back-up generators QRS complex without any p wave, or the p wave would be directly before or after the QRS complex (no p-r interval) and the p wave They only work when they are needed could be inverted Junctional escape rhythms are protective measures to keep the If the patient is on digoxin, suspect digitalis toxicity & check the heart going when the sinus node has failed or is suppressed patients digoxin level 33 34 Other Junctional rhythms Criteria for Junctional Rhythms Accelerated Junctional rhythm: this is when the junctional tissue takes over as the main pacemaker, but the rate exceeds 60 beats Rhythm is usually regular per minute & is still less than 100 beats per minute Intrinsic rate of the AV Junctional tissue is 40-60 beats/minute Accelerated Junctional rhythm is often a sign of digitalis toxicity (so If a junctional rhythm has a rate faster than 60 beats but less than check the patient’s labs; if the dig level is too high, must hold digoxin 100 beats/minute, that is called an accelerated junctional rhythm until the levels returns to a therapeutic level) (suspect dig toxicity) Junctional tachycardia: This is a junctional rhythm greater than If the junctional rate is > 100/minute, that is a junctional tachycardia 100 beats/minute P waves can be absent (due to buried in the QRS) or can appear immediate before or after the QRS complex P-R interval (if present) is shorter than usual 35 36 6  9/18/2024 This concludes the LESSON 04 lecture Please complete Quiz 04. 37 7