Cardiac Arrhythmias Dr Ahmad Hersi Myocardium Muscle Action

Cardiac Arrhythmias Dr. Ahmad Hersi

Myocardium Muscle Action Potential

Normal Cardiac Cycle Systole Diastole Electrical Depolarization “activate” Repolarization “recovery” Mechanical Contract “empty” Relax “fill”

What does it tell us? • • the electrical conduction through the heart areas of ischemia or myocardial damage LV Hypertrophy electrolyte disturbances / drug toxicity

The Electrical System of the Heart SA Node AV Node Bundle of HIS Right Bundle Branch Inter- nodal Tracts Left Bundle Branch Anterior Superior Fascicle Posterior Inferior Fascicle Septal Depolarization Fibers Purkinjie Fibers

Conduction System of the Heart: A Conceptual Model for Illustration SA Node Inter-nodal Tract Left Bundle Branch AV Node Septal Bundle of Depolarization HIS Fibers James Fibers Right Bundle Branch Bundle of Kent Anterior Superior Fascicle Posterior Inferior Fascicle

SA SA Node – “pacemaker” of Node the heart (60 -100 bpm) AV Node – junction of the atria and ventricles (40 -60 bpm) Bundles – Bundle of His connects the AV node to the bundle branches (20 -40 bpm) Bundle of HIS Inter- nodal Tracts

What Is In Each Beat? (the cardiac cycle in waves, complexes, and intervals) • P Wave – atrial contraction or depolarization, (usually upright) • QRS Complex – time for ventricular contraction or depolarization (usually upright) (0. 04 - 0. 12 sec) (delays in the bundle branches will widen the QRS) • T Wave – ventricular repolarization “recharging” (usually upright) • PR Interval – time between atrial depolarization to ventricular depolarization (beginning of P wave to beginning of QRS)(0. 12 - 0. 20 sec) (prolonged PR = delays in the AV node conduction) • QT Interval – represents one complete ventricular depolarization and repolarization (beginning of QRS to the end of the T wave) (0. 32 – 0. 44 sec) (disturbances are usually due to electrolyte disturbances or drug effects)

The ECG Complex with Interval and Segment Measurements

ECG Paper and related Heart Rate & Voltage Computations Memor ize

Reading a Rhythm Strip What Do I Look For? ► Regularity - What is the R – R Interval? ► Rate - Is the rate normal (60 -100), slow, or fast? ***Six-second strip method - (30 big boxes) & multiply times ten ► P Wave – Is there a P wave before every QRS? Is it upright? ► QRS Complex – Is there a normal QRS complex following each P wave? Wide or normal? ► T wave – How does your T wave look? Upright? ► Measure your intervals – PR Interval, QRS, QT

Pacemakers of the Heart • SA Node - Dominant pacemaker with an intrinsic rate of 60 - 100 beats/minute. • AV Node - Back-up pacemaker with an intrinsic rate of 40 - 60 beats/minute. • Ventricular cells - Back-up pacemaker with an intrinsic rate of 20 - 45 bpm. Tehran Arrhythmia Center

Rhythm Analysis • • • Step 1: Step 2: Step 3: Step 4: Step 5: Calculate rate. Determine regularity. Assess the P waves. Determine PR interval. Determine QRS duration. Tehran Arrhythmia Center

Step 1: Calculate Rate 3 sec Option 1 – Count the # of R waves in a 6 second rhythm strip, then multiply by 10. Interpretation? 9 x 10 = 90 bpm Tehran Arrhythmia Center

Step 1: Calculate R wave • Option 2 – Find a R wave that lands on a bold line. – Count the # of large boxes to the next R wave. If the second R wave is 1 large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75, etc. (cont) Tehran Arrhythmia Center

Step 1: Calculate Rate 3 1 1 0 5 0 7 6 5 0 0 0 5 0 0 • Option 2 (cont) – Memorize the sequence: 300 - 150 - 100 - 75 - 60 - 50 Interpretation? Approx. 1 box less than 100 = 95 bpm Tehran Arrhythmia Center

Step 2: Determine regularity R R • Look at the R-R distances (using a caliper or markings on a pen or paper). • Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Irregularly irregular? Interpretation? Regular Tehran Arrhythmia Center

Step 3: Assess the P waves • Are there P waves? • Do the P waves all look alike? • Do the P waves occur at a regular rate? • Is there one P wave before each QRS? Interpretation? Normal P waves with 1 P wave for every QRS Tehran Arrhythmia Center

Step 4: Determine PR interval • Normal: 0. 12 - 0. 20 seconds. (3 - 5 boxes) Interpretation? 0. 12 seconds Tehran Arrhythmia Center

Step 5: QRS duration • Normal: 0. 04 - 0. 12 seconds. (1 - 3 boxes) Interpretation? 0. 08 seconds Tehran Arrhythmia Center

Rhythm Summary • Rate • Regularity • P waves • PR interval • QRS duration Interpretation? 90 -95 bpm Regular Normal 0. 12 s 0. 08 s Normal Sinus Rhythm Tehran Arrhythmia Center

Normal Sinus Rhythm • Normal and constant P wave contours • Normal P wave axis • Rate between 60 and 100 bpm Tehran Arrhythmia Center

Anatomical Aspects of Normal Sinus Node • Located at the superior anterolateral portion of right atrium near its border with the superior vena cava • It is an epicardial structure near sulcus terminalis • From endocardial approach the closest approach is near the superior end of crista terminalis Tehran Arrhythmia Center

Sinus Node Function • • • The dominant cardiac pacemaker Highly responsive to autonomic influences Decreasing rate with vagal stimulation Increasing rate with sympathetic activity Normal sinus rate under basal conditions is 60 -100 bpm. Tehran Arrhythmia Center

Sinus Tachycardia • • • Rate? Regularity? P waves? PR interval? QRS duration? 130 bpm Regular Normal 0. 16 s 0. 08 s Interpretation? Sinus Tachycardia Tehran Arrhythmia Center

Sinus Tachycardia • Sinus rhythm exceeding 100 bpm in adults • Usually between 100 and 180 bpm but may be higher with extreme exertion • Maximum heart arte decreases wit age from near 200 bpm to less than 140 bpm • Gradual onset and termination Tehran Arrhythmia Center

Sinus Tachycardia Tehran Arrhythmia Center

Sinus Tachycardia Causes • Common in infancy and childhood • Normal response to a variety of physiological and pathological stresses – – – Exertion, anxiety Hypovolemia, anemia Fever Congestive heart failure Myocardial ischemia Thyrotoxicosis • Drugs • Inflammation Tehran Arrhythmia Center

Sinus Bradycardia • • • Rate? Regularity? P waves? PR interval? QRS duration? 30 bpm Regular normal 0. 12 s 0. 10 s Interpretation? Sinus Bradycardia Tehran Arrhythmia Center

Sinus Bradycardia • Sinus rhythm at a rate less than 60 bpm • Can result from excessive vagal or decreased sympathetic tone as well as anatomic changes in sinus node • Frequently occurs in healthy young adults, particularly well-trained athletes • Sinus arrhythmia often coexists Tehran Arrhythmia Center

Sinus Bradycardia Tehran Arrhythmia Center

Sinus Bradycardia Junctional Escape Beats Tehran Arrhythmia Center

Sinus Bradycardia Causes • • Hypothyroidism Drugs During vomiting or vasovagal syncope Increased intracranial pressure Hypoxia, hypothermia Depression Jaundice Tehran Arrhythmia Center

Sinus Arrhythmia • • • Rate? Regularity? P waves? PR interval? QRS duration? 50 -75 bpm Phasic variations normal 0. 12 s 0. 10 s Interpretation? Sinus Arrhythmia Tehran Arrhythmia Center

Sinus Pause Tehran Arrhythmia Center

Sick Sinus Syndrome • A combination of symptoms (dizziness, fatigue, confusion, syncope and congestive heart failure) caused by sinus node dysfunction • Atrial tachyarrhythmias may accompany sinus node dysfunction <bradycardia-tachycardia syndrome> Tehran Arrhythmia Center

AV Block Types • First degree AV block • Second degree AV block – Mobitz type I (Wenckebach) – Mobitz type II • Third degree AV block (Complete heart block) • High degree (advanced) AV block Tehran Arrhythmia Center

First Degree AV Block • • • Rate? Regularity? P waves? PR interval? QRS duration? 60 bpm Regular Normal 0. 36 s 0. 08 s Interpretation? 1 st Degree AV Block Tehran Arrhythmia Center

PR Interval PR interval < 0. 12 s 0. 12 -0. 20 s > 0. 20 s High catecholamine states Wolff-Parkinson-White Normal AV nodal blocks Wolff-Parkinson-White 1 st Degree AV Block Tehran Arrhythmia Center

First Degree AV Block • Conduction time is prolonged but all impulses are conducted. • PR interval exceeds 0. 2 sec in adults • Site of conduction delay may be in the AV node (most commonly), in the His-Purkinje system or both. Tehran Arrhythmia Center

First Degree AV Block Tehran Arrhythmia Center

Wenckebach AV Block • • • Rate? Regularity? P waves? PR interval? QRS duration? 50 bpm Regularly irregular Nl, but 4 th no QRS Lengthens 0. 08 s Interpretation? 2 nd Degree AV Block, Type I Tehran Arrhythmia Center

Mobitz Type I Second Degree AV Block • Also called Wenckebach block • Typical type characterized by progressive PR prolongation culminating in a nonconducted P wave • Narrow QRS in most cases Tehran Arrhythmia Center

WB Tehran Arrhythmia Center

Tehran Arrhythmia Center

Wenckebach Block • Atypical pattern in over half the cases • The site of block is almost always in the AV node. • Generally benign and does not advance to more advanced AV block • Can occur in normal children and welltrained athletes Tehran Arrhythmia Center

Mobitz Type II AV Block • • • Rate? Regularity? P waves? PR interval? QRS duration? 40 bpm Regular Nl, 5 th P no QRS 0. 18 s 0. 11 s Interpretation? 2 nd Degree AV Block, Type II Tehran Arrhythmia Center

Mobitz Type II Second Degree AV Block • PR interval remains constant prior to the blocked P wave • Commonly associated with bundle branch blocks Tehran Arrhythmia Center

Tehran Arrhythmia Center

Tehran Arrhythmia Center

Tehran Arrhythmia Center

2: 1 AV Block Tehran Arrhythmia Center

2: 1 AV Block AV Nodal Level Tehran Arrhythmia Center

2: 1 AV Block Infra-nodal Level Tehran Arrhythmia Center

2: 1 AV block Infra-nodal Level Tehran Arrhythmia Center

Complete Heart Block • • • Rate? Regularity? P waves? PR interval? QRS duration? 40 bpm Regular No relation to QRS None Wide (> 0. 12 s) Interpretation? 3 rd Degree AV Block Tehran Arrhythmia Center

Complete AV block • No atrial activity conducts to the ventricles • AV dissociation is present. The atria and ventricles are controlled by independent pacemakers. • Ventricular focus is usually located just below the site of block. • Higher sites are more stable with a more faster escape rate. Tehran Arrhythmia Center

Complete AV block Tehran Arrhythmia Center

Remember • When an impulse originates in a ventricle, conduction through the ventricles will be inefficient and the QRS will be wide and bizarre. Tehran Arrhythmia Center

Tehran Arrhythmia Center

AV Conduction Disturbances Etiology • Degenerative diseases are the most common causes • A variety of other diseases may be responsible: myocardial infarction, drugs, acute infections, infiltrative diseases, neoplasms, etc. • Hypervagotonia Tehran Arrhythmia Center

Tehran Arrhythmia Center

Tehran Arrhythmia Center

Premature Beats • Premature Atrial Contractions (PACs) • Premature Ventricular Contractions (PVCs) Tehran Arrhythmia Center

PAC • • • Rate? Regularity? P waves? PR interval? QRS duration? Interpretation? 70 bpm Occasionally irreg. 2/7 different contour 0. 14 s (except 2/7) 0. 08 s NSR with Premature Atrial Contractions Tehran Arrhythmia Center

Narrow QRS Beats • When an impulse originates anywhere in the atria (SA node, atrial cells, AV node, Bundle of His) and then is conducted normally through the ventricles, the QRS will be narrow (0. 04 - 0. 12 s). Tehran Arrhythmia Center

PVC • • • Rate? Regularity? P waves? PR interval? QRS duration? 60 bpm Occasionally irreg. None for 7 th QRS 0. 14 s 0. 08 s (7 th wide) Interpretation? Sinus Rhythm with 1 PVC Tehran Arrhythmia Center

Wide QRS Beats • When an impulse originates in a ventricle, conduction through the ventricles will be inefficient and the QRS will be wide and bizarre. Tehran Arrhythmia Center

Ventricular Conduction Normal Signal moves rapidly through the ventricles Abnormal Signal moves slowly through the ventricles Tehran Arrhythmia Center

Ventricular Premature Complexes Compensatory Pause Interpolated VPC Tehran Arrhythmia Center

Atrial Fibrillation • • • Rate? Regularity? P waves? PR interval? QRS duration? 100 bpm Irregularly irregular None 0. 06 s Interpretation? Atrial Fibrillation Tehran Arrhythmia Center

Atrial Fibrillation Tehran Arrhythmia Center

Atrial Fibrillation • • • The most common sustained arrhythmia Incidence increases progressively with age. Prevalence: 0. 4% of overall population Mortality rate double that of control AF is characterized by disorganized atrial activity without discrete P waves Tehran Arrhythmia Center

Atrial Fibrillation • Undulating baseline or atrial deflections of varying amplitude and frequency ranging from 350 to 600 bpm. • Irregularly irregular ventricular response. Tehran Arrhythmia Center

Atrial Fibrillation • Morbidity related to: – Excessive ventricular rate – Pause following cessation of AF – Systemic embolization – Loss of atrial kick – Anxiety secondary to palpitations – Irregular ventricular rate Tehran Arrhythmia Center

Atrial Fibrillation • Persistent AF usually in patients with cardiovascular disease – Valvular heart disease – Hypertensive heart disease – Congenital heart disease • Paroxysmal AF may occur with acute hypoxia, hypercapnia or metabolic or hemodynamic derangements • Normal people with emotional stress or surgery or acute alcoholic intoxication • Lone AF Tehran Arrhythmia Center

Atrial Fibrillation • Therapeutic Goals: – Control of ventricular rate – Restoration and maintenance of sinus rhythm – Prevention of thromboembolism Tehran Arrhythmia Center

CHADS 2 Score and Risk of Stroke JAMA 2001; 285: 2864 Tehran Arrhythmia Center

Atrial Flutter • • • Rate? Regularity? P waves? PR interval? QRS duration? 70 bpm Regular Flutter waves None 0. 06 s Interpretation? Atrial Flutter Tehran Arrhythmia Center

Atrial Flutter • Regular atrial tachyarrhythmia with atrial rate between 250 -350 bpm. • Flutter waves are seen as saw-tooth like atrial activity Tehran Arrhythmia Center

Atrial Flutter • Atrial Flutter is a form of atrial reentry localized to right atrium. • Typically the ventricular rate is half the atrial rate, but the ventricular response may be 4: 1, 2: 1, 1: 1 etc. Tehran Arrhythmia Center

Atrial Flutter Circuit Tehran Arrhythmia Center

Atrial Flutter • Most often in patients with organic heart disease • Usually less long-lived than AF and may convert to AF. • Control of ventricular rate is difficult in atrial flutter • The most effective treatment is DC cardioversion Tehran Arrhythmia Center

PSVT • • • Rate? Regularity? P waves? PR interval? QRS duration? Interpretation? 74 148 bpm Regular regular Normal none 0. 16 s none 0. 08 s Paroxysmal Supraventricular Tachycardia Tehran Arrhythmia Center

Paroxysmal Supraventricular Tachycardia (PSVT) • Usually at a rate of 150 -250 bpm • No organic heart disease in the majority • Presentations – Palpitations – Chest discomfort, dyspnea, lightheadedness – Frank syncope – SCD Tehran Arrhythmia Center

Preexcitation Tehran Arrhythmia Center

VT • • • Rate? Regularity? P waves? PR interval? QRS duration? 160 bpm Regular None Wide (> 0. 12 sec) Interpretation? Ventricular Tachycardia Tehran Arrhythmia Center

Ventricular Arrhythmias Definitions • Premature Ventricular beats – Single beats – Ventricular Bigeminy, the appearance of one PVC after each sinus beat – Couplets, two consecutive premature beats – Triplets, three consecutive premature beats – Salvos, runs of 3 -10 premature beats • Accelerated Idioventricular Rhythm (Slow VT), rate 60100 bpm • Ventricular Tachycardia (VT), rate over 100 bpm • Ventricular Flutter, regular large oscillations at a rate of 150 -300 bpm • Ventricular Fibrillation (VF), irregular undulations of varying contour and amplitude Tehran Arrhythmia Center

Ventricular Tachycardia Classification • Duration – Sustained VT defined as VT that persists for than 30 s or requires termination because of hemodynamic collapse – Nonsustained VT, 3 beats to 30 s • Morphology – Monomorphic – Polymorphic Tehran Arrhythmia Center

Salvos Tehran Arrhythmia Center

Sustained Monomorphic VT Tehran Arrhythmia Center

Sustained Polymorphic VT Tehran Arrhythmia Center

VT Etiology • VT generally accompanies some form of structural heart disease most commonly: – Ischemic heart disease – Cardiomyopathies • Primary electrical abnormalities – Long QT syndromes – Brugada syndrome • Idiopathic VT Tehran Arrhythmia Center

VF • • • Rate? Regularity? P waves? PR interval? QRS duration? None Irregularly irreg. None Wide, if recognizable Interpretation? Ventricular Fibrillation Tehran Arrhythmia Center

Sudden Death Syndrome • Incidence – 400, 000 - 500, 000/year in U. S. – Only 2% - 15% reach the hospital – Half of these die before discharge • High recurrence rate Tehran Arrhythmia Center

Clinical Substrates Associated with VF Arrest • • • Coronary artery disease Idiopathic cardiomyopathy Hypertrophic cardiomyopathy Long QT syndrome RV dysplasia Rarely: WPW syndrome Tehran Arrhythmia Center