PEPconnect

Cardiac Electrophysiology

This web based training course will provide the imaging professional with the basics of the electrophysiology of the heart and how it’s interpreted on ECGs. The tropics that are covering in this training include basics of electrophysiology, the electrocardiogram, common electrophysiology conditions, treatment devices and procedures,  and an overview of congestive heart failure.

Welcome to this Web Based Training on Cardiac Electrophysiology By the end of this course, you will be able to: Describe the electrical structure of the heart and how it affects cardiac mechanics. List the steps in ECG interpretation. Describe the most common electrophysiological conditions Describe the procedures and treatment devices used to correct electrophysiological conditions Fundamentals of Electrophysiology The Electrocardiogram Common Electrophysiology Conditions Treatment Devices Congestive Heart Failure 1800s Early 1900s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s First graphic documentation of ventricular fibrillation (1850) Tawara- conduction system of the mammalian heart (1906) Reciprocating tachycardia (1921) Wolf-Parkinson-White Syndrome is described (1930) Establishing the existence of ventricular vulnerability (1940) Radio frequency induction method (1959) D.C. Defibrillator is developed (1962) Ventricular fibrillation (1971) Catheter technique, chest ablation. atrioventricular system (1982) Transvenous Implantable Defibrillator Fundamentals of Electrophysiology Pumping generates pulse or heartbeat Begins at the upper chambers (atria) Blood pumps into lower chambers (ventricles) Ventricles pump blood to the body and lungs Electrical stimulus is generated by the SA node. (60-100 times per minute) Atria are activated Stimulus travels down to ventricles and causes them to contract. Conductivity Path Impulses travel from the SA node to the AV node. Continue to the Bundle of His (divides into the right and left pathways) Bundle branches stimulate the right and left ventricles. Four characteristics that integrate the heart’s electrical and mechanical activity: Automaticity – The ability to initiate an impulse or stimulus. The cardiac conduction system pacemaker cells have this inherent capacity. Excitability – the ability to respond to an impulse or stimulus. The atria and ventricle cells respond to the impulse of the pacemaker cells by depolarizing and repolarizing. Conductivity – the ability to transmit impulses to other areas.  Cardiac conduction system cells and muscle fibers both have this property. Contractility – the ability to respond to stimulus with mechanical action  Cardiac muscle fibers respond mechanically to electrical stimulation by contracting. Image courtesy of www.theindustryherald.com   The Electrocardiogram Dedicated to the study and management of cardiac arrhythmias. Evaluated as part of the evaluation of patient symptoms: Weakness Shortness of Breath Fatigue Chest pain Observe rhythm regularity Measure heart rate Evaluate the P waves Evaluate lead II Evaluate PR interval Access the QRS complex Signals are administered to the heart muscle in patterns to stimulate ventricular tachycardia. Electrodes placed near tissue in heart that conducts electrical impulses to ID electrical system abnormalities. Evaluate: Diagnose source of symptoms Effectiveness of medications Risk of Sudden Cardiac Death Need for pacemaker, implantable cardioverter defibrillator, or ablation Survived an episode of sudden cardiac death Syncope of unknown cause. Recurrent wide complex Compromised hemodynamics and/or syncope with Wolf Parkinson White (WSW) Syndrome Second degree AV block with syncope Prior to surgical or ablation treatment Detect aberrant cardiac rhythms Arrhythmia must be identified Type of arrhythmia Focal Reentrant P:  Wave contraction of the atria Q,R,S : Waves due to contraction of ventricles T : Wave the recovery of the ventricles U : The origin of this wave is still under debate; thought to possibly be the recovery of the atria; normally not displayed since it is thought to be covered up by the ventricular recovery (T wave) Chambers undergo alternating periods of relaxation and contraction Relaxation period called DIASTOLE Contraction period called SYSTOLE Time is measured along the horizontal axis. Each small square = 1mm = 0.04 seconds Each larger square = 5mm = 0.2 seconds Voltage is measured along the vertical axis Each 10mm = 1mV in voltage P wave Normally no more than 3mm high and 0.12 seconds in duration Indicates atrial depolarization (and physiologic contraction) PR interval Normally lasts no longer than 0.20 seconds in duration (5 small squares) Indicates atrioventricular (AV) conduction time QRS complex Normal duration is less than 0.12 seconds (3 small squares) Indicates ventricular depolarization (and physiologic contraction) R wave deflected positively, while Q and S deflect negatively   ST segment Normally not depressed more than 0.5mm Indicates a “rest” period between ventricular depolarization and repolarization T wave No more than 5mm high (10mm in precordial leads) Indicates ventricular repolarization QT interval Usually less than half the RR interval Total ventricular depolarization and repolarization time (Na- influx and K+ efflux) RR interval – measurement of Heart Rate     Voltage Between Electrodes Polarity Bipolarity + and - poles Unipolarity Negative pole made up of signals from other electrode Vectors of Depolarization and Repolarization Vector 1 – Depolarization of atrial (P wave) Vector 2 – Ventricular septum (1st deflection of QRS) Vector 3 – Bulk of ventricular muscle (QRS complex) Vector 4 – Repolarization of ventricular muscle (T wave) General direction of the heart’s depolarization wavefront or mean electrical vector in the frontal plane Impulse towards the electrode = Positive Away from the electrode = Negative More directly toward or away from electrode,  the greater the amplitude In this section, we are going to discuss common electrophysiological conditions and problems. Most common type of supraventricular tachycardia Atria don’t contract Blood forms pools and may clot High risk for stroke 30% of embolic stroke victims have A-fib as a risk factor. Risk for development increases with age. Medications only 50-60% effective. Treatment: Cardioversion (short term) Radio Frequency Ablation (long term) Coronary artery disease (CAD) Thyroid disease High blood pressure Lung disease Pericarditis Genetic tendencies Pulmonary disease Lifestyle changes Medications (only 50-60% effective) Acetylsalicylic acids (ASAs) Coumadin Beta Blockers Treatments Cardioversion (not permanent) Radio frequency ablation of pulmonary ostia (long term treatment) Caused by a single electrical wave that usually circulates rapidly in the right atrium. Can increase risk of stroke. Symptoms: Steady but fast heart rate Shortness of breath Fatigue Dizziness Syncope Chest pain Sweating Heart Failure Previous Heart Attack Acquired or congenital valve abnormalities High Blood Pressure Recent upper chamber surgery Thyroid dysfunction Alcoholism (especially binge drinking) Chronic lung disease Acute (serious) illness Diabetes Lifestyle changes Treatment Medications Cardioversion Radio frequency ablation (long term) 3rd most common type of supra-ventricular tachycardia (SVT). Originates in the area of the AV node. Functional re-entrant circuits are caused by the following types of myocardial tissue: Normal Fast Injured Slow Some people born with 2 pathways within AV node Myocardial infarction is a major cause. Considered an isolated rhythm disturbance Not considered life threatening Lifestyle modification can reduce symptoms Avoid Caffeine Alcohol Sleep deprivation Stress Anxiety Frequency and severity fluctuates Little to be done by the patient. Depends on frequency and severity of the symptoms. Patient can perform to terminate symptoms: Valsalva maneuver Carotid massage Medications: Beta Blockers Calcium Channel Blockers Digoxin Permanent Treatment Catheter ablation Some people born with accessory pathway between atria and the ventricles. Less than 2 in 1000 people Visible on ECG by short P-R interval and a delta wave. Symptoms Palpitations Dizziness or lightheadedness Shortness of breath Fainting Fatigue Anxiety Extra electrical pathway allows electrical impulses to bypass the AV node. Ventricles and activated too early. Major rhythm disturbances: Looped electrical impulses Ventricles pump very quickly, causing rapid heartbeat Disorganized electrical impulses Ventricles don’t have time to fill with blood then do not pump enough blood to the body. Vagal maneuvers Can slow heartbeat Medications Anti-arrhythmic medications Medications that slow heart rate Other Treatments Cardioversion Radiofrequency catheter ablation Does not require AV junction, accessory pathways or ventricular tissue for initiation and maintenance. Occurs in persons with normal hearts as well as structurally abnormal hearts. Normal heart structure – low mortality rate Underlying heart disease – higher mortality rate. Symptoms Rapid heart rate Sudden onset of palpitations Dyspnea Dizziness Lightheadedness Chest pressure Syncope Medications: Anti-arrhythmic medications AV nodal blocking agents Beta blockers Calcium channel blockers Cardioversion Radiofrequency catheter ablation Surgical ablation Electrical impulses originating in the AV junction. AV Node Area above and below AV Node Causes: CHF Valvular disease Cardiomyopathy Treatment AV junctional ablation Pacemaker implantation Rapid heart beats arising in the lower chambers of the ventricles Chaotic heart beat Ventricles begin to fribrillate Life threatening Sudden cardiac death Cardiac arrest Result from: Damage caused by myocardial infarction Cardiac surgery Other conditions that affect ventricular muscle Catheter Ablation is used less often to treat Multiple origins and circuits Usually occurs in a diseased heart Contractions occur too fast and out of sync Heart unable to pump blood effectively. Leads to cardiac arrest Can also be triggered by episodes of ventricular tachycardia Treatment: Implantable devices AICD In this section, we will talk about treatment devices used in the EP lab. Assist physician understanding of the nature of arrhythmias. Test electrical activity of the heart to find where the arrhythmia is coming from. Evaluate the effectiveness of medications Physician inserts a specialized electrode catheter designed for EP studies. Sends electrical signals to the heart and record its electrical activity. Implanted in the chest to monitor for episodes of rapid heart beat and correct them. Correct heart rhythms that are too fast – tachycardias. V-Tach Stimulates the hear to restore a normal rhythm. V-Fib Gives and electric shock to reset the heart beat Corrects heart rhythms that are too slow Bradycardias Non-surgical Uses bursts of radiofrequency energy to destroy extra electrical pathways in the heart. EP study is done to map the location of the arrhythmia Fluoroscopy is used to guide ablation catheters Used as permanent treatment for: AVNRT WPW Syndrome A-Fib A-Flutter AV Junction tachycardia Atrial tachycardia Ventricular tachycardia Restores heart rhythm in arrhythmia patients Treats: A-Fib A-Flutter A-Tach V-Tach 2 types: Electrical Cardioversion Electrical shocks to the heart through electrodes placed on the chest. Pharmacological Cardioversion Uses medication to restore heart rhythm. For A-Fib: Flecainide Dofetiliede Propafone Amiodarone Ibutilide For SVT Adenosine Verapramil Image courtesy of www.heartandhealth.com     You should now be able to: Describe the electrical structure of the heart and how it affects cardiac mechanics. List the steps in ECG interpretation. Describe the most common electrophysiological conditions Describe the procedures and treatment devices used to correct electrophysiological conditions  American Heart Association. Electrophysiology Studies (EPS). www.heart.org    University of Minnesota. Atlas of Human Cardiac Anatomy. www.vhlab.umn.edu    Medscape. Cardiovascular System Anatomy. https://emedicine.medscape.com/article/1948510-overview    Mayo Clinic. Electrocardiogram (ECG or EKG).  https://www.mayoclinic.org/tests-procedures/ekg/about/pac-20384983    WebMD. What are Heart Rhythm Disorders (Arrhythmias)?. https://www.mayoclinic.org/tests-procedures/ekg/about/pac-20384983    Charles Patrick Davis.  Arrythmias (Heart Rhythm Disorders). https://www.emedicinehealth.com/heart_rhythm_disorders/article_em.htm    L. Brent Mitchell, MD. Overview of Abnormal Heart Rhythms. https://www.merckmanuals.com/home/heart-and-blood-vessel-disorders/abnormal-heart-rhythms/overview-of-abnormal-heart-rhythms    American Heart Association. Conduction Disorders.  https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/conduction-disorders

  • Cardiac Electrophysiology