1 Lecture Notes Chapter 19 Electrocardiogram and Cardiac Arrhythmias Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

2 Helpful Hints  Depolarize = Depolarize = Contracts  Systolic  Afterload  Repolarize = Repolarize = Recover  Diastolic  Preload

3 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 Plots electrical activity that creates depolarization and repolarization Leads are placed on chest, arms, and legs Leads are placed on chest, arms, and legs Bipolar standard limb leads Bipolar standard limb leads Unipolar limb and chest leads Unipolar limb and chest leads Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

4 Wave is considered one wave… A complex is considered multiple waves or letters… For example, the P Wave that we’ll see is comprised of one letter… the P… and it shows us the “kick” of the atria… shooting that last 20% into the ventricle… Then the QRS wave is considered a complex because there’s three stages… and this is when the Ventricle contracts or depolarizes… The T wave represents the Ventricle Relaxing….Pg 344 AMPLITUDE = VOLTAGE Ventricles are much larger in muscle mass, they generate more voltage when they depolarize or contract… You will see that the voltage or height that the Ventricles generate is much higher than the atria..

5 ECG Components  Waves and complexes  P wave = atrial depolarization  QRS complex = ventricular depolarization 0.08 to 0.10 sec 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.

6 Fig Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. ECG Components

7 ConceptQuestion 19-1  A high amplitude P wave may be associated with what type of abnormality? Let’s think about the right atrium for a moment… What can cause the Right Atrium CVP to be high? ANSWERS: Right heart failure Cor Pulmonale Tricuspid Stenosis Tricuspid Regurg. An abnormally high P-wave amplitude means the atrial muscle mass is greater than normal

8 ECG Components  Intervals and segments  PR interval - From SA node to ventricles From SA node to ventricles 0.12 to 0.20 sec ( slower the HR – longer PR) 0.12 to 0.20 sec ( slower the HR – longer PR) (longer HR – shorter PR)  point QRS -represents the ventricular contraction… Q is the beginning of ventricles… S would represent the end of the contraction… The point in which after the S, the tracing reaches baseline… this is known as the J point… QRS -represents the ventricular contraction… Q is the beginning of ventricles… S would represent the end of the contraction… The point in which after the S, the tracing reaches baseline… this is known as the J point…  ST segment Represents the Ventricle beginning it’s recovery phase… or its diastolic phase Flat, lying on baseline is normal Flat, lying on baseline is normal Depressed >0.5 mm = Myocardial ischemia Depressed >0.5 mm = Myocardial ischemia Elevated >2 mm = myocardial injury Elevated >2 mm = myocardial injury Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

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10 ECG Components  Intervals and segments  QT interval Beginning of the QRS complex to the End of the T- wave… Beginning of the QRS complex to the End of the T- wave… Usually less than 40 seconds Usually less than 40 seconds The ventricle is in the refractory period The ventricle is in the refractory period  Refractory Period Refractory Period = When ventricle is contracting, should another electrical activity try to come quickly, the ventricle will not respond… It cannot accept another depolarizing/contracting signal during this phase… It can’t stack it’s contraction… Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

11 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  Clinical Focus 19-1 pg 347 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

12 ECG Graph Paper Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig. 19-5

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14 ECG Leads pg 349 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig. 19-9

15 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.

16 Normal Sinus Rhythm Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig Heart Rate _______

17 Abnormal Sinus Rhythms  Tachycardia  Sinus tachycardia HR >100 beats/min HR >100 beats/min Regular and rhythmic Regular and rhythmic Causes Causes  Exercise, fever, anxiety, pain, coffee, smoking, hypoxia  Beta adrenergic drugs Treatment: OXYGEN… Then, focus on underlying cause Treatment: OXYGEN… Then, focus on underlying cause Additional Treatment: Vagal Stimulation Additional Treatment: Vagal Stimulation = Carotid Massage = Carotid Massage  A rapid heart rate will icrease workload of heart and increase O2 requirements Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

18 Abnormal Sinus Rhythms Tachycardia Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig Heart Rate _______

19 Abnormal Sinus Rhythms Bradycardia  Bradycardia  Sinus bradycardia HR <60 beats/min HR <60 beats/min Regular and rhythmic Regular and rhythmic Normal in sleep, physically conditioned individuals Normal in sleep, physically conditioned individuals Carotid sinus syndrome; overly sensitive pressure receptors (vagal) in the neck… If stimulated = syncope Carotid sinus syndrome; overly sensitive pressure receptors (vagal) in the neck… If stimulated = syncope SYNCOPE = _________________ SYNCOPE = _________________ Gagging can also cause bradycardia (Suctioning) Gagging can also cause bradycardia (Suctioning) Symptomatic bradycardia Symptomatic bradycardia  hypotension, weakness, sweating, syncope Treatment: atropine; pacemaker Treatment: atropine; pacemaker Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

20 Abnormal Sinus Rhythms Bradycardia Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig Heart Rate _______

21 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.

22 Abnormal Sinus Rhythms Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig

23 ConceptQuestion 19-4  Why do chronic congestive heart failure and high atrial pressures predispose a person to the development of atrial fibrillation?

24 Ventricular Tachycardia Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig

25 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 Epinephrine, Amiodarone, Lidocaine Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

26 Ventricular Fibrillation Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. Fig

27 ASYSTOLE