Cardiac Conduction Disorders & Rhythm PDF

Chapter 28: Disorders of Cardiac Conduction and Rhythm Copyright © 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins Cardiac Conduction System  Controls the rate and direction of electrical impulse conduction in the heart o Impulses are generated in the SA node, whic...

Chapter 28: Disorders of Cardiac Conduction and Rhythm Copyright © 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins Cardiac Conduction System  Controls the rate and direction of electrical impulse conduction in the heart o Impulses are generated in the SA node, which has the fastest rate of firing, and travel to the Purkinje system in the ventricles.  In certain areas of the heart, the myocardial cells have been modified to form the specialized cells of the conduction system.  The conduction system maintains the pumping efficiency of the heart. Copyright © 2020 Wolters Kluwer All Rights Reserved Electrocardiography  Twelve leads  Diagnostic ECG o Each providing a unique view of the electrical forces of the heart  Diagnostic criteria are lead specific.  Improper lead placement can significantly change the QRS morphology. o Misdiagnosis of cardiac arrhythmias or the presence of conduction defects can be missed. Copyright © 2020 Wolters Kluwer All Rights Reserved Copyright © 2020 Wolters Kluwer All Rights Reserved  5 Copyright © 2020 Wolters Kluwer All Rights Reserved Goals of Continuous Bedside Cardiac Monitoring  Shifted from simple heart rate and arrhythmia monitoring to o Identification of ST segment changes o Advanced arrhythmia identification o Diagnose o Provide treatment Copyright © 2020 Wolters Kluwer All Rights Reserved Question #1  Is the following statement true or false?  The electrocardiogram is a reflection of cardiac muscle contraction. You can directly diagnose specific defects in muscle activity. Copyright © 2020 Wolters Kluwer All Rights Reserved Answer to Question #1  False  Rationale: The electrocardiogram is a reflection of cardiac muscle contraction. You can directly diagnose specific defects in muscle activity. Copyright © 2020 Wolters Kluwer All Rights Reserved Types and Causes of Disorders of the Cardiac Conduction System  Types o Disorders of rhythm o Disorders of impulse conduction  Causes o Congenital defects or degenerative changes in the conduction system o Myocardial ischemia and infarction o Fluid and electrolyte imbalances o Effects of drug ingestion Copyright © 2020 Wolters Kluwer All Rights Reserved Types of Arrhythmias #1  Sinus Node Arrhythmias o Sinus bradycardia o Sinus tachycardia o Sinus arrest  Arrhythmias of Atrial Origin o Paroxysmal supraventricular tachycardia o Atrial flutter o Atrial fibrillation Copyright © 2020 Wolters Kluwer All Rights Reserved Types of Arrhythmias #2  Junctional Arrhythmias  Disorders of Ventricular Conduction and Rhythm  Long QT Syndrome and Torsades de Pointes  Ventricular Arrhythmias o Premature ventricular contractions o Ventricular tachycardia o Ventricular flutter and fibrillation Copyright © 2020 Wolters Kluwer All Rights Reserved Diagnostic Methods  Signal-averaged electrocardiogram  Holter monitoring  Exercise stress testing  Electrophysiologic studies  QT dispersion Copyright © 2020 Wolters Kluwer All Rights Reserved Copyright © 2020 Wolters Kluwer All Rights Reserved Pharmacologic Treatment of Arrhythmias  Class I drugs: act by blocking the fast sodium channels  Class II agents: β-adrenergic–blocking drugs that act by blunting the effect of sympathetic nervous system stimulation on the heart  Class III drugs: act by extending the action potential and refractoriness  Class IV drugs: act by blocking the slow calcium channels, thereby depressing phase 4 and lengthening phases 1 and 2 Copyright © 2020 Wolters Kluwer All Rights Reserved Correction of Conduction Defects, Bradycardias and Tachycardias  Electronic pacemaker o Temporary o Permanent  Cardioversion o Defibrillation o Synchronized  Ablation  Surgical interventions Copyright © 2020 Wolters Kluwer All Rights Reserved Copyright © 2020 Wolters Kluwer All Rights Reserved Copyright © 2020 Wolters Kluwer All Rights Reserved Question #2  Sinus arrhythmias will have a greater affect on the total heart than atrial arrhythmias because________. A. they will not be different, and each is equally harmful B. the sinus node will directly cause a fibrillation C. the sinus node will stimulate the rest of the heart directly into a new rhythm D. the sinus node will not activate the atrioventricular node Copyright © 2020 Wolters Kluwer All Rights Reserved Answer to Question #2  C. the sinus node will stimulate the rest of the heart directly into a new rhythm Copyright © 2020 Wolters Kluwer All Rights Reserved