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EKG Interpretation > Dubin Ch 5 Rhythm > Flashcards

Dubin Ch 5 Rhythm Flashcards

0
Q

What causes the SA node pacing rate to varie almost imperceptibly?

A

Respiration

Pg 100

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1
Q

True or false. All automaticity foci pace with a regular rhythm?

A

True

Pg 99

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2
Q

The atrial conduction system consists of three specialized internodal tracks in the right atrium, name them.

Name the conduction tract that innervates the left atrium.

A

Anterior, middle, posterior

Bachman’s bundle

Pg 101

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3
Q

From where do the three conduction pathways in the right atrium originate and terminate?

A

Originate from the SA node and terminate at the AV node

Pg 101

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4
Q

What wave is produced by atrial depolarization?

A

P wave

Pg 101

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5
Q

What is the coronary sinus?

A

The hearts own venous drainage system that empties into the right atrium

Pg 101

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6
Q

What produces a pause on an EKG between a P-wave and the QRS complex?

A

The slowing of conduction in the AV node

Pg 102

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7
Q

Does the proximal or distal end of the AV node have automaticity foci?

A

The distal end, aka, AV junction

Pg 102

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8
Q

QRS complex represents what?

A

Ventricular depolarization

Pg 103

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9
Q

Why does left to right depolarization of the septum occur?

A

The left bundle branch produces fine terminal filaments, the right bundle branch does not, so left to right depolarization occurs before the rest of the ventricular myocardium depolarizes.
Pg 104

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10
Q

Ventricular depolarization persists through the end of the __________.

A

T-wave

Pg 104

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11
Q

Ventricular contraction begins and ends during…

A

The QT interval

Pg 104

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12
Q

What is it U wave?

A

It represents the final phase of Purkinje repolarization and occurs following the T-wave
Pg 104

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13
Q

If an automaticity foci suddenly becomes irritable will it pace fast or slow?

A

Very fast

Pg 105

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14
Q

Name the general categories that arrhythmias can be divided into.

A 
Irregular rhythms
escape
premature beats
tachy-arrhythmias
These are categorized according to the mechanism of origin
Pg 106
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15
Q

What are irregular rhythms usually caused by and how can they be classified?

A

Usually caused by multiple active automaticity sites

A wandering pacemaker
Multifocal atrial tachycardia
Atrial fibrillation
Pg 107

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16
Q

Describe what is meant by the term parasystolic when referring to an automaticity foci.

A

In a heart with structural pathology or hypoxia, foci may suffer from an “entrance” block. Any incoming depolarization is blocked, thereby they cannot be overdrive suppressed while their own automaticity is still conducting to surrounding tissues.
Pg 107

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17
Q

Describe a wandering pacemaker rhythm.

A 
An irregular rhythm produced by the pacemaker activity wandering from the SA node to nearby atrial automaticity foci.
Cycle length variation
Variation in the shape of P waves.
Rate <100.
Pg 108
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18
Q

Describe multifocal atrial tachycardia (MAT).

A 
Irregular rhythm
P-wave shape varies
Atrial rate >100
Irregular ventricular rhythm
Atrial foci show early signs of parasystole (entrance block) by developing a resistance to overdrive suppression. No single foci achieves pacemaking dominance. They all pace together.
Pg 109
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19
Q

What health conditions is MAT associated with?

A

COPD and sometimes digitalis toxicity

Pg 109

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20
Q

Describe atrial fibrillation.

A 
Irregular rhythm
Continuous chaotic atrial spikes
Irregular ventricular rhythm
Continuous rapid multiple atrial foci. No single impulse depolarizes the atria completely. Only random atrial depolarization's reach the AV node. This produces irregular QRS complexes. 
Pg 110
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21
Q

How do you determine the general ventricular rate in a fib?

A

By counting the number of QRS complexes in a six second strip and multiply by 10.
Pg 110

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22
Q

What is an escape rhythm and what are the three types of escape rhythm?

A 
An automaticity focus escapes overdrive suppression to pace at it's inherent rate. 
Atrial escape rhythm
Junctional escape rhythm
Ventricle escape rhythm
Pg 112
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23
Q

What is an escape beat and what are the three types of escape beats?

A 
Automaticity focus transiently escapes overdrive suppression to emit one beat.
Atrial Escape Beat
Junctional Escape Beat
Ventricle Escape Beat
Pg 112
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24
Q

Describe escape

A

The response of an automaticity focus to a pause in the pacemaking activity
Pg 112

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25
Q

What rhythm occurs when SA node pacing ceases entirely and an automaticity focus paces at it inherent rate?

A

Sinus Arrest and an Escape rhythm

Pg 112-113

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26
Q

Why are automaticity foci overdrive suppressed?

A

Because they are depolarized by a pacing rate faster than it’s own inherent pacing rate.
Pg 113

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27
Q

Describe sinus block.

A

The SA node misses one pacing cycle and produces a transient pause. An automaticity focus produces an escape beat in an attempt to become the dominant pacer but the return of SA node pacing, overdrive suppresses it again.
Pg 113

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28
Q

Describe an atrial escape rhythm

A

Originates in an atrial automaticity focus
P waves are not identical to previous P waves produced by the SA node.
Inherent rhythm is 60-80 BPM.
Pg 114

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29
Q

Describe a Junctional Escape Rhythm (idojunctional rhythm)

A

If there is sinus arrest accompanied by atrial foci failure, automaticity focus in the AV junction escapes overdrive suppression and becomes the dominant pacemaker with a rate of 40-60 BPM.
Can also occur due to a complete block in the proximal AV node.
Pg 115

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30
Q

What is the exception to a junctional escape rhythm producing a series of lone QRS complexes?

A

Retrograde Atrial Depolarization. Characterized by an inverted P-wave in leads with an upright QRS.
Pg 116

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31
Q

Describe retrograde atrial depolarization.

A

Occurs when junctional automaticity focus conducts to the ventricles as expected, but also depolarize the atria from below. This produces an inverted P-wave in EKG leads with an upright QRS.
Pg 116

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32
Q

What are the 3 patterns retrograde atrial depolarization may record on an EKG?

A

Inverted P-wave immediately prior to each QRS
Inverted P-wave after each QRS
Inverted P-wave buried with in each QRS
Pg 116

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33
Q

Describe ventricular escape rhythm.

A

If a ventricular automaticity focus is not depolarized from above it escapes overdrive suppression and becomes the dominant pacemaker with an inherent rate of 20-40 BPM
Pg 117

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34
Q

Ventricular escape rhythms result from one of two mechanisms. What are they?

A
  1. A complete conduction block below the AV node and ventricular foci are not stimulated by atrial depolarizations
  2. SA node, Atrial foci, and AV junction foci all fail and produce a condition called “downward displacement of the pacemaker”. The ventricle foci become the pacemaker in an attempt to sustain life.
    Pg 117
35
Q

What is Stokes-Adams?

A

Unconsciousness caused by poor brain perfusion due to pacing from the ventricular foci

36
Q

What happens in transient sinus block with the SA node?

A

The SA node misses a pacing stimulus that produces a pause and an atrial focus emits an escape beat. (A.K.A.atrial escape beat)
p118-119

37
Q

What does the EKG look like for an atrial escape beat?

A

A pause of one cardiac cycle is followed by a P-wave that differs from the other P waves
p119

38
Q

What is a junctional escape beat?

A

When a transient sinus block is present junctional automaticity foci can emit an escape beat. It may produce retrograde atrial depolarization, with an inverted P-wave immediately before or after the QRS.
p120

39
Q

What is a ventricular escape beat?

A

Occurs when the atrial and junctional foci fail to suppress a ventricular escape beat. This happens in excessive parasympathetic innervation. On an EKG it will produce an enormous QRS complex.
p121

40
Q

What is a premature beat?

A

It is caused by an irritable foci that fire spontaneously and earlier than expected. Ventricular foci are very sensitive to oxygen. If low oxygen is sensed, they react.

41
Q

Atria and junctional foci become irritable due to what types of conditions?

A

Usually adrenergic stimulants such as Epi, caffeine or any beta-1 receptors stimulants. Also any increased sympathetic stimulation, some toxins and hypothyroidism, low O2.
p123

42
Q

What is a premature atrial beat?

A

A premature beat that produces an earlier P-wave than expected due to an irritable atrial foci. The P-wave is unusually shaped and maybe hiding on the peak of the T-wave, the T-wave will look taller than the others.
p124

43
Q

Can a premature atrial beat reset the rhythm based on the premature beat?

A

Yes, if a retrograde depolarization occurs to the dominant automaticity center, usually the SA node. If not, it will not reset the rhythm.
p125

44
Q

What does the EKG look like of a premature atrial beat with aberrant ventricular conduction?

A

Early P-wave that does not look like all the others, followed by a wide QRS complex. This is due to one of the bundle branches not completely repolerizing and remaining slightly refractory.
p126

45
Q

What is a non-conducted premature atrial beat?

A

When a premature atrial depolarization reaches the AV node prior to its repolarization, it is not conducted to the ventricles resulting in no QRS on an EKG.
p128

47
Q

What is a premature Junctional beat?

A

A premature fire of the AV junction that stimulates the ventricle and sometimes the atria.
p131

48
Q

What should you expect to see on an EKG with a PJB?

A

A premature QRS complex that is slightly widened

p 131

49
Q

What does a PJB look like on an EKG if it depolarizes the atria in a retrograde fashion?

A

In inverted P wave with an upright QRS

50
Q

Describe Junctional Bigeminy and Junctional Trigeminy

A

Bigeminy- A PJB occurs after each normal SA node cycle

Trigeminy- a PJB occurs after 2 consecutive cycles

51
Q

Describe atrial bigeminy and atrial trigeminy.

A

A premature atrial beat that couples to the end of a normal cycle and repeats itself is atrial bigeminy. If it couples itself after two normal cycles, it is trigeminy.
EKG look for a premature P-wave in each couplet.
p. 133

52
Q

What causes ventricular irritability?

A

Low O2, Low K+, Specific Pathology

p.135

53
Q

Describe what a PVC is and what it looks like on an EKG.

A

Represents a premature, irritable ventricular foci that creates a wider, taller and deeper QRS complex that usually has the opposite deflection of the main QRS’s. (one area of the ventricular wall depolarizes before the rest of the wall.
p.135

54
Q

What is a compensatory pause after a PVC?

A

The PVC does not reset the SA node, so it continues to fire on schedule, so the next P-wave does fire but the ventricles are refractory and so there is a pause until the following P-wave and QRS.
p. 137

55
Q

How many PVC/min is considered pathological, and what do identical PVC indicate?

A

6, they are emanating from the same irritable ventricular focus (hypoxia)
p.138

56
Q

Describe Ventricular Bigeminy, Trigeminy and Quadgeminy

A

Bi- PVC’s coupled with every normal cycle
Tri - PVC’s coupled with every 2 normal cycles
Quad - PVC’s couple with every 3 normal cycles
p. 139

57
Q

Describe Ventricular Parasystole

A

When a ventricular foci escapes :overdrive suppression” and is able to fire at its own inherent rate. (dual rhythm)
p. 140

58
Q

How can PVCs resemble V-tach?

A

A run of 3 or more consecutive PVCs is basically the same thing as V-tach, only not lasting. (very irritable ventricular foci). If lasting > 30s = V-tach
p. 141

59
Q

Describe Multifocal PVCs

A

Multiple ventricular focus are firing, each producing its own unique, identifiable PVC. Indicates severe cardiac hypoxia
p. 142

60
Q

What is Mitral Valve Prolapse and how can it cause PVCs?

A

During ventricular systole the mitral valve prolapses into the atria and pulls on the chordae where it attaches to the ventricle. This causes stretch and ischemia leading to irritable ventricular foci.
p.143

61
Q

Why is a “R on T” dangerous?

A

When a PVC fires on a T wave or too soon after, the ventricle is still trying to repolarize and this can lead to dangerous arrythmias.
p. 144

62
Q

What are the three main types of tacy-arrythmias and their rate ranges?

A

Paroxysmal Tachycardia 150-250, Flutter 250-350, Fibrilation 350-450
p. 145

63
Q

What are the 3 types of Paroxysmal (sudden) tachycardia?

A

Atrial, Junctional, Ventricular

p.148

64
Q

Describe PAT

A

Rapid firing of atrial foci that overdrive suppress the SA node at a rate of 150-250. P waves don’t look normal but do conduct to create a normal QRS.
p.149

65
Q

What is PAT with block look like and what can cause it?

A

rate 150-250
2 P-waves per QRS
Caused by digitalis excess or toxicity
p. 150

66
Q

Describe PJT and what it looks like

A

Irritable Foci in the AV Junction, may produce retrograde atrial depolarization resulting in an inverted P-wave before, after or within each QRS. May produce a wide QRS due to unequal refractory of R/L Bundle Branches
p.151

67
Q

Common name for PAT and PJT

A

PSVT (SVT)

68
Q

Is there independent pacing of the atria and ventricles in PVT? Describe PVT

A

yes
SA node still paces the atria but P wave is typically not visible due to large QRS (a.k.a AV dissociation)
PVT is actually runs of PVC’s with a rate of 150-250
p. 154

69
Q

Possible indications of PVT

A

Coronary insufficiency and poor oxygenation, can lead to irritable ventricular foci
p.156

70
Q

What could cause SVT to look like VT?

A

SVT with aberrant conduction produces wide QRS. Also a Bundle Branch Block w/ SVT will widen QRS complex.
NEVER give Adenosine to a pt. with VT
p. 156

71
Q

Distinguish between SVT and VT

A

SVT = QRS.14 sec, AV dissociation is common, Extreme right axis deviation is common, CVD is common
p. 157

72
Q

What does Torsades de Point look like?

A

Brief episodes of 250-350 ventricular rhythm that look like a twisted ribbon.
p.158

73
Q

Describe atrial flutter

A

rapid back-to-back atrial depolarization waves at a rate of 250-350, where only 1 out of every 2 or 3 conduct through the AV node to the ventricles due to its long refractory period. Looks like “saw teeth”.
p. 159

74
Q

What can you do to assist in identifying atrial flutter?

A

Invert the strip or employ a vagal maneuver to see if the “saw teeth” waves are then revealed
p.160

75
Q

How does a vagal maneuver help identify atrial flutter?

A

By increasing AV node refractoriness and allowing fewer atrial fluters to be conducted to the ventricles.
p.160

76
Q

What does ventricular flutter look like?

A

Rapid rate 250-350 with smooth “sine” waves of similar amplitude that rarely resolves itself.
p. 161

77
Q

What does ventricular flutter almost always progress into?

A

V-Fib

78
Q

If a paroxysmal tachycardia has identifiable P waves and normal QRS it could not have originated in an irritable ___________, and therefor must be ____________

A

ventricle focus
some type of supra ventricular tachycardia
p. 163

79
Q

Define fibrillation

A

erratic rhythm caused by continuous rapid discharges from foci in either the atria or ventricle. These foci suffer from entrance block and are parasystolic. The can not be overdrive suppressed
p. 164

80
Q

Describe atrial fibrillation

A

Many irritable parasystolic atrial foci rapidly fire and only occasional depolarizations are conducted through the AV node to the ventricles resulting in an irregular ventricular rate
p. 165

81
Q

Identify A-fib on an EKG

A

Irregularly irregular, with no discernible P waves. Treat the ventricular rate appropriately if it is out of a safe range.
p. 166

82
Q

Describe ventricular fibrulation

A

Many irritable parasystolic ventricular foci rapidly fire and only depolarize small sections of the ventricle resulting in twitching of the ventricles
p. 167

83
Q

Identify VF on an EKG

A

Totally erratic appearance and lack of identifiable waves on an EKG
p. 168

84
Q

Describe Wolf-Parkinsons-White

A

When the bundle of Kent “bypasses” the delay of the AV node and prematurely excites the ventricles. Causes the illusion of a shortened PRI and lengthened QRS.
p. 171

85
Q

Describe Lown-Ganong-Levine Syndrome

A

The AV node is bypassed by the James Bundle, an extension of the anterior internal tract, and conducts atrial depolarizations past the AV node delay directly to the Bundle of His. Can result in very fast ventricular rates in patients with rapid atrial rates.
p. 172

EKG Interpretation (6 decks)

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