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Lecture Notes Chapter 18 Electrocardiogram and Cardiac Arrhythmias Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 1 Helpful Hints Depolarize = Depolarize = Contracts Systolic Afterload Repolarize = Repolarize = Recover Diastolic Preload 2 Normal Electrocardiogram (ECG) EKG Electrocardiograph Detects micro-voltage changes as the heart depolarizes and repolarizes How? - Leads ECG “leads” (electrode configurations) • Plots electrical activity that creates depolarization and repolarization • Leads are placed on chest, arms, and legs • Bipolar standard limb leads • Unipolar limb and chest leads Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 3 ECG Components Waves and complexes P wave = atrial depolarization QRS complex = ventricular depolarization • 0.08 to 0.10 sec T wave = ventricular repolarization Wave height (amplitude) = voltage Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 4 ECG Components Fig. 18-2 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 5 ConceptQuestion 18-1 A high amplitude P wave may be associated with what type of abnormality? 6 ECG Components Intervals and segments PR interval • From SA node to ventricles • 0.12 to 0.20 sec J point • QRS _______________________________________ ST segment • Flat, lying on baseline is normal • Depressed >0.5 mm = ________________________ • Elevated >2 mm = ________________________________ Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 7 8 ECG Components Intervals and segments QT interval • ________________________________________ • Usually less than __________ seconds • The ventricle is in the refractory period Refractory Period ____________________________________ Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 9 ECG Graph Paper Grid 1 mm (smallest square) vertical = 0.1 mV 1 mm horizontal = 0.04 sec Heavy 5 mm lines (big square) = 0.20 sec & 0.5 mV 5 large squares = 25 mm (about 1 inch) = 1 sec 25 mm/sec graph speed Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 10 ECG Graph Paper Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig. 18-5 11 12 ECG Leads Fig. 18-9 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 13 Hexaxial Reference Figure Fig. 18-11 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 14 Identifying Common Arrhythmias Systematic ECG analysis Steps 1: Identify waves and complexes 2: Analyze QRS complexes 3: Analyze P waves 4: Assess AV relationship Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 15 Identifying Common Arrhythmias Box 18-2 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 16 Normal Sinus Rhythm Sinus node initiates each depolarization Rate: 60 to 100 beats/min P wave-QRS complex ratio is 1:1 Spacing between QRS is constant PR interval is <0.16 sec Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 17 Normal Sinus Rhythm Heart Rate _______ Fig. 18-16 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 18 Abnormal Sinus Rhythms Tachycardia Sinus tachycardia • HR >100 beats/min • Regular and rhythmic • Causes Exercise, fever, anxiety, pain, coffee, smoking, hypoxia Beta adrenergic drugs • Treatment: OXYGEN… Then, focus on underlying cause • Additional Treatment: Vagal Stimulation • =_____________________________________ A rapid heart rate __________________________ Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 19 Abnormal Sinus Rhythms Tachycardia Heart Rate _______ Fig. 18-17 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 20 Abnormal Sinus Rhythms Bradycardia Bradycardia Sinus bradycardia • HR <60 beats/min • Regular and rhythmic • Normal in sleep, physically conditioned individuals • Carotid sinus syndrome; overly sensitive pressure receptors (vagal) in the neck… If stimulated = syncope • SYNCOPE = _________________ • Gagging can also cause bradycardia (Suctioning) • Symptomatic bradycardia hypotension, weakness, sweating, syncope • Treatment: atropine; pacemaker Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 21 Abnormal Sinus Rhythms Bradycardia Heart Rate _______ Fig. 18-18 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 22 Abnormal Sinus Rhythms Sinus arrhythmia Irregularly generated sinus node impulses Alternate between fast and slow rates Irregular spacing between QRS complexes Follows inspiration & expiration (↑rate insp.; ↓exp.) No clinical significance and do not require treatment Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 23 Abnormal Sinus Rhythms Fig. 18-19 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 24 Premature Atrial Contraction (PAC) Ectopic focus fires = early atrial contraction QRS complexes are ____________ but ___________ _____________ Stress, alcohol, tobacco, caffeine, electrolyte imbalances, sympathetic stimulation Drugs: sodium & calcium channel inhibitors may be used: quinidine: verapamil Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 25 Premature Atrial Contraction (PAC) Fig. 18-20 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 26 Supraventricular Arrhythmias “Above the Ventricles” Atrial flutter Single ectopic pacemaker above AV node Ectopic focus produces F waves (saw-toothed) • “P waves are now F waves” AV node normally blocks transmission of many Fwaves Atrial rate 200-350 bpm and regular; thus QRS rate is regular, but slower than atrial rate Symptoms: palpitations, nervousness, anxiety, possible syncope if inadequate ventricular filling time ++ blockers; electrical cardioversion Treatment: Ca Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 27 Supraventricular Arrhythmias A-Flutter Every 4th atrial impulse is transmitted to ventricles, producing a regular QRS rhythm. Fig. 18-21 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 28 Supraventricular Arrhythmias Atrial fibrillation Multiple randomly firing ectopic atrial foci Atria “quiver” (no pumping) at 300-600 impulses/min; completely irregular Loss of atrial kick = reduced ventricular filling→ reduced stroke volume & CO; occasional peripheral pulse deficit Fine fibrillatory waves; slightly wavy baseline (no “Ps”) Slower, irregular ventricular rate Causes: conditions that ↑ atrial pressure & enlarge atria: longer depolarization route May cause hypotension, fainting (syncope) Pooling of blood in atria: thromboembolism risk: anticoagulant drugs important preventative treatment Treatment: Ca++ blockers; electrical cardioversion Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 29 Supraventricular Arrhythmias A-Fib Fig. 18-22 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 30 Junctional Arrhythmias AV node assumes role of pacemaker Junctional escape rhythm if SA node fails to fire Inherent rate of 40 to 60 bpm QRS normal shape and duration Retrograde (backward) atrial conduction Irritable junctional fibers cause PJC Junctional tachycardias Inverted, hidden, or retrograde P waves (after QRS) Paroxysmal (PSVT): up to 240/min (caffeine, nicotine, alcohol, overexertion, electrolyte imbalance, etc.) Nonparoxysmal (150/min): ↑junctional excitability (drug toxicity) Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Treatment: vagal stimulation; IV adenosine; IV Ca++ blocker 31 ConceptQuestion 18-4 Why do chronic congestive heart failure and high atrial pressures predispose a person to the development of atrial fibrillation? 32 Junctional Arrhythmias Fig. 18-24 Inverted P waves; slow heart rate Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 33 Junctional Arrhythmias Junctional Tachycardia Fig. 18-25 No P waves Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 34 Ventricular Arrhythmias Premature ventricular contraction (PVC) Ectopic focus/excitability arises from ventricles QRS not preceded by P wave Wide (>0.12 sec) and bizarre appearance Generate T wave of opposite polarity (downward) Followed by compensatory pause Frequent PVCs signal life-threatening arrhythmia potential; highly irritable ventricular muscle fibers Unifocal vs. multifocal PVCs Bigeminy Treatment: antiarrhythmic drug: lidocaine OXYGEN! Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 35 Ventricular Arrhythmias Unifocal PVCs Fig. 18-26 Multifocal PVCs: serious ventricular irritability Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 36 Ventricular Arrhythmias Ventricular tachycardia (V-Tach) Successive “runs” of PVCs Rate of 110-250/min Treat as emergency: serious sign of ventricular irritability QRS complexes bizarre and wide High potential to progress to ventricular fibrillation Treat with IV lidocaine or amiodarone Cardioversion Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 37 Ventricular Tachycardia Fig. 18-28 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 38 Ventricular Arrhythmias Ventricular fibrillation (VF) Most lethal arrhythmia = cardiac arrest; CODE BLUE Ventricles nonfunctional, quivering, no pumping ability No recognizable waves or complexes Requires electrical defibrillation—no drug can convert to normal rhythm Equivalent to Cardiac Arrest. CPR must be initiated SHOCKABLE RHYTHM Along with a shock, use: • Epinephrine, Amiodarone, Lidocaine Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 39 Ventricular Fibrillation Fig. 18-29 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 40 ASYSTOLE 41