1 lecture notes chapter 19 electrocardiogram and cardiac arrhythmias copyright © 2007, 1998 by...

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Lecture NotesLecture NotesChapter 19Chapter 19

Electrocardiogram and Electrocardiogram and Cardiac ArrhythmiasCardiac Arrhythmias

Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

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Helpful HintsHelpful Hints

Depolarize = Depolarize = ContractsDepolarize = Depolarize = Contracts SystolicSystolic AfterloadAfterload

Repolarize = Repolarize = RecoverRepolarize = Repolarize = Recover DiastolicDiastolic PreloadPreload

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Normal Electrocardiogram (ECG)Normal Electrocardiogram (ECG)EKGEKG

ElectrocardiographElectrocardiograph Detects micro-voltage changes as the heart Detects micro-voltage changes as the heart

depolarizes and repolarizesdepolarizes and repolarizes

How? - LeadsHow? - Leads ECG “leads” (electrode configurations)ECG “leads” (electrode configurations)

• Plots electrical activity that creates depolarization and Plots electrical activity that creates depolarization and repolarizationrepolarization

• Leads are placed on chest, arms, and legsLeads are placed on chest, arms, and legs

• Bipolar standard limb leadsBipolar standard limb leads

• Unipolar limb and chest leadsUnipolar limb and chest leads


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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 = VOLTAGEVentricles 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..

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ECG ComponentsECG Components

Waves and complexesWaves and complexes P wave = atrial depolarizationP wave = atrial depolarization QRS complex = ventricular depolarizationQRS complex = ventricular depolarization

• 0.08 to 0.10 sec0.08 to 0.10 sec

T wave = ventricular repolarizationT wave = ventricular repolarization Wave height (amplitude) = voltageWave height (amplitude) = voltage


6Fig. 19-2 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

ECG ComponentsECG Components

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ConceptQuestion 19-1ConceptQuestion 19-1

A high amplitude P wave may be associated A high amplitude P wave may be associated with what type of abnormality?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 failureCor PulmonaleTricuspid StenosisTricuspid Regurg.

An abnormally high P-wave amplitude means the atrial muscle mass is greater than normal

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ECG ComponentsECG Components Intervals and segmentsIntervals and segments

PR interval -PR interval -• From SA node to ventriclesFrom 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)(longer HR – shorter PR)

pointpoint• QRS -QRS -represents the ventricular contraction… Q is represents the ventricular contraction… Q is

the beginning of ventricles… S would represent the the beginning of ventricles… S would represent the end of the contraction… The point in which after the end of the contraction… The point in which after the S, the tracing reaches baseline… this is known as S, the tracing reaches baseline… this is known as the J point… the J point…

ST segment ST segment Represents the Ventricle beginning it’s Represents the Ventricle beginning it’s recovery phase… or its diastolic phaserecovery phase… or its diastolic phase

• Flat, lying on baseline is normal Flat, lying on baseline is normal

• Depressed >0.5 mm = Myocardial ischemiaDepressed >0.5 mm = Myocardial ischemia

• Elevated >2 mm = myocardial injuryElevated >2 mm = myocardial injuryCopyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

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ECG ComponentsECG Components Intervals and segmentsIntervals and segments

QT intervalQT interval• Beginning of the QRS complex to the End of the T-Beginning of the QRS complex to the End of the T-

wave… wave…

• Usually less than 40 secondsUsually less than 40 seconds

• The ventricle is in the refractory periodThe ventricle is in the refractory period

Refractory PeriodRefractory Period

Refractory Period = When ventricle is contracting, Refractory Period = When ventricle is contracting, should another electrical activity try to come should another electrical activity try to come quickly, the ventricle will not respond… It cannot quickly, the ventricle will not respond… It cannot accept another depolarizing/contracting signal accept another depolarizing/contracting signal during this phase… It can’t stack it’s contraction… during this phase… It can’t stack it’s contraction…


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ECG Graph PaperECG Graph Paper

GridGrid 1 mm (smallest square) vertical = 0.1 mV1 mm (smallest square) vertical = 0.1 mV 1 mm horizontal = 0.04 sec1 mm horizontal = 0.04 sec Heavy 5 mm lines (big square) = 0.20 sec & 0.5 Heavy 5 mm lines (big square) = 0.20 sec & 0.5

mVmV 5 large squares = 25 mm (about 1 inch) = 1 sec5 large squares = 25 mm (about 1 inch) = 1 sec

25 mm/sec graph speed25 mm/sec graph speed

Clinical Focus 19-1 pg 347Clinical Focus 19-1 pg 347


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ECG Graph PaperECG Graph Paper

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

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ECG Leads ECG Leads pg 349pg 349


Fig. 19-9

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Normal Sinus RhythmNormal Sinus Rhythm

Sinus node initiates each depolarizationSinus node initiates each depolarization Rate: 60 to 100 beats/minRate: 60 to 100 beats/min P wave-QRS complex ratio is 1:1P wave-QRS complex ratio is 1:1 Spacing between QRS is constantSpacing between QRS is constant PR interval is <0.16 secPR interval is <0.16 sec


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Normal Sinus RhythmNormal Sinus Rhythm


Fig. 19-16

Heart Rate _______

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Abnormal Sinus RhythmsAbnormal Sinus Rhythms TachycardiaTachycardia

Sinus tachycardiaSinus tachycardia• HR >100 beats/minHR >100 beats/min

• Regular and rhythmicRegular and rhythmic

• CausesCauses Exercise, fever, anxiety, pain, coffee, smoking, hypoxiaExercise, fever, anxiety, pain, coffee, smoking, hypoxia Beta adrenergic drugsBeta adrenergic drugs

• Treatment: OXYGEN… Then, focus on underlying causeTreatment: OXYGEN… Then, focus on underlying cause

• Additional Treatment: Vagal StimulationAdditional Treatment: Vagal Stimulation

• = = Carotid MassageCarotid Massage

A rapid heart rate will icrease workload of heart A rapid heart rate will icrease workload of heart and increase O2 requirementsand increase O2 requirements


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Abnormal Sinus RhythmsAbnormal Sinus RhythmsTachycardiaTachycardia


Fig. 19-17

Heart Rate _______

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Abnormal Sinus RhythmsAbnormal Sinus RhythmsBradycardiaBradycardia

BradycardiaBradycardia Sinus bradycardiaSinus bradycardia

• HR <60 beats/minHR <60 beats/min

• Regular and rhythmicRegular and rhythmic

• Normal in sleep, physically conditioned individualsNormal in sleep, physically conditioned individuals

• Carotid sinus syndrome; overly sensitive pressure Carotid sinus syndrome; overly sensitive pressure receptors (vagal) in the neck… If stimulated = syncopereceptors (vagal) in the neck… If stimulated = syncope

• SYNCOPE = _________________SYNCOPE = _________________

• Gagging can also cause bradycardia (Suctioning)Gagging can also cause bradycardia (Suctioning)

• Symptomatic bradycardiaSymptomatic bradycardia hypotension, weakness, sweating, syncopehypotension, weakness, sweating, syncope

• Treatment: atropine; pacemakerTreatment: atropine; pacemaker


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Abnormal Sinus RhythmsAbnormal Sinus RhythmsBradycardiaBradycardia


Fig. 19-18Heart Rate _______

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Abnormal Sinus RhythmsAbnormal Sinus Rhythms

Sinus arrhythmiaSinus arrhythmia Irregularly generated sinus node impulsesIrregularly generated sinus node impulses Alternate between fast and slow ratesAlternate between fast and slow rates Irregular spacing between QRS complexesIrregular spacing between QRS complexes Follows inspiration & expiration (Follows inspiration & expiration (↑rate insp.; ↓exp.)↑rate insp.; ↓exp.) No clinical significance and do not require No clinical significance and do not require

treatmenttreatment


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Abnormal Sinus RhythmsAbnormal Sinus Rhythms


Fig. 19-19

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ConceptQuestion 19-4ConceptQuestion 19-4

Why do chronic congestive heart failure and Why do chronic congestive heart failure and high atrial pressures predispose a person to high atrial pressures predispose a person to the development of atrial fibrillation?the development of atrial fibrillation?

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Ventricular TachycardiaVentricular Tachycardia


Fig. 19-28

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Ventricular ArrhythmiasVentricular Arrhythmias Ventricular fibrillation (VF)Ventricular fibrillation (VF)

Most lethal arrhythmia = Most lethal arrhythmia = cardiac arrest;cardiac arrest; CODE BLUECODE BLUE Ventricles nonfunctional, quivering, no pumping abilityVentricles nonfunctional, quivering, no pumping ability No recognizable waves or complexesNo recognizable waves or complexes Requires electrical defibrillationRequires electrical defibrillation—no drug can convert to —no drug can convert to

normal rhythmnormal rhythm Equivalent to Cardiac Arrest. CPR must be initiatedEquivalent to Cardiac Arrest. CPR must be initiated

SHOCKABLE RHYTHMSHOCKABLE RHYTHM

Along with a shock, use:Along with a shock, use:

• Epinephrine, Amiodarone, LidocaineEpinephrine, Amiodarone, LidocaineCopyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc.

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Ventricular FibrillationVentricular Fibrillation


Fig. 18-29

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ASYSTOLEASYSTOLE

1 lecture notes chapter 19 electrocardiogram and cardiac arrhythmias copyright © 2007, 1998 by...

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