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Module 15 > ECG and Dysrhythmias in Small Animals > Flashcards

ECG and Dysrhythmias in Small Animals Flashcards

1
Q

what is the P wave

A

atrial depolarization

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2
Q

what occurs during the P wave (5)

A
  1. SA node cells in RA spontaneously depolarize –> depolarizes adjacent RA cells
  2. wave of depolarization moves towards the left
  3. cells in left atrium are at rest and a dipole is created –> positive end is closer to the positive electrode so get a upward trace
  4. when all RA and LA are depolarized the trace returns to base line
  5. next delay is the wave of depolarization passing through the atrioventricular node to the ventricles
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3
Q

what is the Q wave

A

early ventricular depolarization

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4
Q

what occurs in the Q wave

A
  1. wave of depolarization passes down the interventricular septum
  2. wave of depolarization spreads from left to right creating a dipole
  3. negative end of the dipole is closer to the + electrode so it creates a negative deflection on the ECG trave
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5
Q

what is the R wave

A

ventricular depolarization

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6
Q

what occurs in the R wave (4)

A
  1. endocardium depolarizes before the epicardium
  2. dipole is created which is very large since the number of cardiomyocytes within the left ventricle are numerous
  3. the positive end of the dipole is closer to the + electrode so it creates an upward deflection on ECG trace
  4. a dipole is created towards the left since the ventricular apex is directed towards the left and the left ventricle is much larger than the right and dominates
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7
Q

what is the S wave

A

late ventricular depolarization

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8
Q

what occurs in the S wave (3)

A
  1. the wave of depolarization finishes spreading from the endocardium to the epicardium of both ventricles
  2. the ECG returns to baseline and can sometimes go negative
  3. the negative end of the dipole is closer to the + electrode –> downward deflection in trace
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9
Q

what is the T wave

A

ventricular repolarization

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10
Q

what occurs in the T wave (3)

A
  1. the epicardium is the last to depolarize but the first to repolarize
  2. epicardial cells are now positive on the extracellular surface and create a dipole with the endocardial cells which are still depolarized
  3. positive end of the dipole is closer to the + electrode –> upward deflection in ECG occurs
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11
Q

what is the PR interval

A

PR: time between atrial depolarization and ventricular depolarization

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12
Q

what is the QT interval

A

length of time between the ventricles remain depolarized

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13
Q

what is the QRS complex interval

A

time take for the ventricular depolarization to occur once the wave of depolarization has passed through the AVN from the atria

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14
Q

what is the PP interval

A

time between atrial depolarizations

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15
Q

what is the RR interval

A

time between ventricular depolarizations

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16
Q

what are the uses of the ECG (4)

A
  1. diagnosis of arrhythmias noted on clincal exam
  2. rule in/out arrythmias in animals with a history of collapse
  3. provide info regarding chamber enlargement
  4. information on certain electrolyte disturbances (K+)
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17
Q

how are ECGs analyzed (8)

A
  1. heart rate (slow/normal/fast)
  2. heart rhythm (regular/irregular/chaotic)
  3. P:QRS ratio (1:1)
  4. relationship of P to Q-P-Q interval
  5. P and QRS complex variation
  6. normal complex measurement
  7. QT interval, ST segment & T waves
  8. assess the significance of any arrhythmias detected
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18
Q

how is the heart rate measured

A

count Y beats in 6s

Y x 10 = beats/min

with 25 mm/s paper speed (need to know)

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19
Q

what can you look for when assessing the rhythm (4)

A
  1. early beats
  2. delays
  3. fibrillation
  4. ectopic beats
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20
Q

what do you look at when looking at P:QRS ratio and relationship (3)

A
  1. check distance between P wave and the QRS complex. Is it too long?
  2. is there a P wave before the QRS
  3. is there a P wave without QRS
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21
Q

what is wandering pacemaker

A

P wave variation: tall wave and short wave

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22
Q

what are QRS complex variations

A
  1. venticular ectopies either from left ventricle or right ventricle
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23
Q

what occurs during an abnormal ventricular activation pattern from the left ventricle

A

sometimes called a right bundle branch block pattern QRS complex

electrical signal spreads through in an abnormal direction –> spread cranially –> negative QRS

wide bizarre QRS

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24
Q

what is an abnormal ventricular activation pattern from the right ventricle

A

sometimes called a left bundle branch block pattern QRS complex.

electrical activity travels from the right ventricle and travels from cranial to caudal which creates a positive QRS

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25
Q

what are the differences between premature and escape beats

A
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26
Q

what are P wave changes (3)

A
  1. absent: atrial standstill
  2. wide P waves: left atrial dilation
  3. tall P waves: right atrial dilation
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27
Q

what change is shown here

A

atrial standstill

absent P wave

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28
Q

what is shown here

A

wide P waves

left artial dilation

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29
Q

what abnormality is shown here

A

tall P waves

right atrial dilation

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30
Q

what are common QRS changes (4)

A
  1. tall R: left ventricular enlargement
  2. deep S: right ventricular enlargement
  3. small complexes: pleural effusion, obesity
  4. small variable height complexes: pericardial effusion
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31
Q

what is shown here

A

tall R left ventricular enlargement (also T wave is large)

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32
Q

what change is shown here

A

deep S

right ventricular enlargement

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33
Q

what is shown here

A

small complexes

pleural effusion, obesity

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34
Q

what is shown here

A

small variable height complexes

pericardial effusions

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35
Q

what could be causes of a prolonged QT interval (4)

A
  1. hypocalcemia
  2. hypokalemia
  3. hypothermia
  4. drugs (sotalol)
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36
Q

what are causes of shortened QT intervals (3)

A
  1. hypercalcemia
  2. hyperkalemia
  3. drugs (digoxin)
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37
Q

what does a prolonged QT cause

A

excessive intracellular calcium and possibly a rapid, fatal ventricular tachycardia called Torsade de Pointes

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38
Q

what does ST segment depression indicate

A

hypoxia

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39
Q

what is shown here

A

ST segment depression

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40
Q

what does ST segment coving indicate

A

left ventricular enlargement

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41
Q

what is shown here

A

ST segment coving

left ventricular enlargement

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42
Q

when are arrhythmias treated (3)

A
  1. causing signs in their own right (syncope)
  2. potentially life-threatening (ventricular tachycardia)
  3. no underlying immediately treatable cause
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43
Q

what are the classifications of rhythms (3)

A
  1. normal
  2. bradyarrhythmias
  3. tachyarrhythmias
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44
Q

what are normal rhythms (2)

A
  1. sinus rhythm
  2. sinus arrythmia (normal for dogs)
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45
Q

what rhythm is shown here

A

sinus rhythm

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46
Q

what rhythm is shown here

A

sinus arrhythmia

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47
Q

what are bradyarrhythmias (8)

A
  1. sinus arrest
  2. sick sinus syndrome
  3. sinus bradycardia
  4. atrial standstill
  5. primary AV block
  6. second degree AV block: mobitz type 1
  7. second degree AV block: mobitz type 2
  8. 3rd degree/complete AV block
48
Q

what are the causes of a sinus arrest (2)

A
  1. medication: sedatives, beta blockers, calcium channel blockers, digoxin
  2. diseases: high vagal tone, atrial disease, hypothyroidism
49
Q

what is sinus arrest

A

complete sessation SA node activity

normal beats but there is a pause –> followed by a ventricular ectopic beat which would be an escape because it follows a pause

50
Q

what are arrhythmia is shown

A

sinus arrest

51
Q

how do you treat sinus arrhythmias

A

address underlying problem

52
Q

what breed might sinus arrest be normal for

A

brachycephalic

53
Q

what can sinus arrest be accentuated by

A

general anesthesia

54
Q

what rhythm is shown here

A

sick sinus syndrome

sinus tachycardia?

55
Q

what breeds have a hereditary component to sick sinus syndrome

A

mini schnauzer

west highland white terrier

56
Q

what diseases cause sick sinus tachycardia

A

idiopathic

may also have spells of tachycardia

57
Q

how is sick sinus syndrome treated (3)

A
  1. pacemaker
  2. sympathomimetics: theophylline, propentofylline, terbutaline
  3. parasympathomimetics: propantheline
58
Q

what is sinus bradycardia

A

sinus rhythm –> but very slow <60 in dogs, <100-120 in cats

beats of normal sinus origin and conduction, often regular

59
Q

when can sinus bradycardia be normal (3)

A
  1. excessive vagal tone
  2. athletic animals
  3. normal rhythm under GA if not too slow if BP is acceptable
60
Q

what are the causes of sinus bradycardia (3)

A
  1. medication: sedatives (ACP), drugs used to treat tachyarhythmias
  2. disease: hypothyroidism, increased intracranial pressure, dysautonomia, eletrolyte imbalances
  3. metabolic: hypothermia
61
Q

how is sinus bradycardia treated

A

address the underlying problem

62
Q

what is shown here

A

sinus bradycardia

63
Q

what is atrial standstill

A

no P wave, regular QRS, followed by large spikey T waves

64
Q

what rhythm is shown

A

atrial standstill

no P wave, regular QRS followed by large spikey T waves

65
Q

what are the causes of atrial standstill (2)

A
  1. persistent: idiopathic, presumed atrial cardiomyopathy, muscular dystrophies, treated by pacing but prognosis is poor
  2. temporary: hyperkalemia (hypoadrenocorticism, oliguric renal failure)
66
Q

how is atrial standstill treated

A

address underlying problem

67
Q

what is first degree AV block

A

P wave then a delay before QRS complex

68
Q

when is a first degree AV block normal

A

can be normal in dogs with slow heart rates esp during sleep

69
Q

what can cause a first degree AV block (2)

A
  1. drugs: sedatives, tachyarrhythmia drugs
  2. disease: high vagal tone, fibrosis of AV node
70
Q

what is a second degree AV block mobitz type 1

A

occasional P wave occurs without QRS-T complex

71
Q

what rhythm is shown here

A

first degree AV block

delay after P wave

72
Q

when can 2nd degree AV block mobitz type 1 be normal

A

in dogs with high vagal tone or alseep

normal in horses

73
Q

what are the causes of 2nd degree AV block mobitz type 1 (2)

A
  1. diseases causing high vagal tone
  2. regular cycle of (several) dropped beats is more likely to be associated with progressive myocardial disease and may progres to 3rd degree AV block
74
Q

how are 2nd degree AV block mobitz type 1 treated

A

address the underlying problem if possible but not usually symptomatic

75
Q

what is the atropine response test

A

record ECG

give atropine s/c 0.04 mg/kg

approx 30 min later record a second ECG

if the arrythmia is gone –> then it is vagal in origin (HR usually >150)

76
Q

what is a 2nd degree AV block mobitz type 2

A

Don’t see progressive lengthening of the PR interval and there is much more frequent dropping of beats and more frequent isolated P waves often in a an irregular (alternating between conductive and dropped beats)

77
Q

what does a 2nd degree AV block mobitz type 2 indicate

A

significant and indicates AV node disease

78
Q

what are the causes of 2nd degree AV block mobitz type 2

A
  1. diseases: AV node fibrosis, infiltration
79
Q

how is 2nd degree AV block mobitz type 2 treated

A

pace if symptomatic often progresses to 3rd degree block

80
Q

what rhythm is shown here

A

2nd degree AV block mobitz type 2

81
Q

what is a 3rd degree/complete AV block

A

P waves and QRS-T complexes are completely dissocaited

normal P waves occur but the ventricles are activated at a slower rate from a junctional or ventricular focus –> escape beats look bizarre

82
Q

what is the arrhythmia shown here

A

3rd degree/complete AV block

P waves and QRS-T complexes are completely dissociated

83
Q

what are the causes of 3rd degree/complete AV block

A
  1. diseases: AV node fibrosis, AV node infiltration, lyme disease
84
Q

what is the treatment of 3rd degree/complete AV block (3)

A
  1. pacemaker
  2. sypathomimetics: theophylline, propentofylline, terbutaline
  3. parasympatholytics: propantheline
85
Q

what can a 3rd degree/complete AV block represent

A

serious myocardial disease or toxemia or conduction system degeneration but often myocardial function is otherwise preserved

86
Q

what arryhthmia is shown here

A

3rd degree/complete AV block with no escape beats

87
Q

what are the tachycarrythmias (7)

A
  1. sinus tachycardia
  2. supraventricular premature beat
  3. atrial fibrillation
  4. supraventricular/atrial tachycardia
  5. ventricular premature complex (VCP)
  6. ventricular tachycardia
  7. rapid ventricular tachycardia
88
Q

what is sinus tachycardia

A

normal P-QRS-T complexes of SA node origin but at a higher than normal rate, regular rhythm

can be normal finding in nervous or excitable dogs (even up to 280-300)

89
Q

what are the causes of sinus tachycardia

A
  1. medication: drugs used to treat bradycardia
  2. disease: anemia, pain, pyrexia, resp distress or in response to hypovolemia, shock, dehydration, septicemia, decreased CO, hyperthyroidism, hypertension under GA or due to cardiac failure
90
Q

how is the sinus tachycardia treated

A

address underlying problem but not usually treated

91
Q

what arrhythmia is this

A

sinus tachycardia

92
Q

what is supraventricular premature beat

A

ectopic beat from the myocardium

can’t see P wave and if its there its abnormal in conformation

QRS-T complex is normal

93
Q

what arryhthmia is shown

A

supraventricular premature beat

94
Q

what causes supraventricular premature beats

A
  1. disease: atrial fibrillation, atrial fibrosis, systemic diseases such as pyrexia, neoplastic diseases
95
Q

how is supraventricular premature beat treated

A

address underlying problem, but not treated specifically

96
Q

what is atrial fibrillation

A

absent P waves which are replaced by fibrillation waves

QRS-T complexes are normal in conformation but are rapid and erratic (chaotic) rhythm

97
Q

what are the causes of atrial fibrillation

A
  1. disease: atrial dilation, atrial infiltration, atrial fibrosis, occult dilated cardiomyopathy/lone atrial fibrillation
  2. larger dogs, uncommon in cats
98
Q

what is the most common treated atrial arrhythmia in dogs

A

atrial fibrillation

99
Q

how is atrial fibrillation treated

A

slow down ventricular rate, slow conduction through AV node

  1. digoxin
  2. usually with diltiazem
  3. (atenolol)
100
Q

what is supraventricular/atrial tachycardia

A

bursts of atrial ectopic beats

101
Q

what are the causes of supraventricular/atrial tachycardia

A
  1. congenital: by-pass tract (Wolf-Parkinson-White syndrome) –> bridging the atrial to the ventricular myocardium and bypassing the AV node and allowing rapid circuit of impulses going down the AV node and going back up the bypass tract
  2. disease: atrial dilation, atrial infiltration, atrial fibrosis, systemic disease
102
Q

what is the treatment of supraventricular/atrial tachycardia (4)

A
  1. digoxin
  2. diltiazem
  3. atenolol
  4. sotalol ablation of by-pass tract
103
Q

what is shown here

A

atrial fibrillation

104
Q

what is shown here

A

supraventricular/atrial tachycardia

105
Q

what is ventricular premature complex (VCP)

A

no P wave present (except by coincidence)

QRS-T complex is premature and prolonged duration and bizarre in shape often with a large, slurred S-T segment and T wave

106
Q

what is paroxysmal ventricular tachycardia

A

ventricular premature complexes can occur as single or pairs or as rapid bursts

107
Q

what is shown here

A

ventricular premature complexes (VCP)

108
Q

what are the causes of ventricular premature complex (3)

A
  1. disease: ventricular myocardial dilation, inflammation, infiltration, fibrosis
  2. systemic disease: anemia, septicemia, splenic mass, gastric dilation, pyometra
  3. metabolic: electrolyte imbalance (hypokalemia)
109
Q

how is ventricular premature complex treated

A

address underlying problem, but not treated specifically

110
Q

what is ventricular tachycardia

A

runs of ectopic beats

can cause syncope and is life threatening

111
Q

what is shown here

A

ventricular tachycardia

112
Q

what are the causes of ventricular tachycardia

A
  1. disease: ventricular myocardial dilation, inflammation, infiltration, fibrosis
  2. systemic disease: anemia, septicemia, splenic mass (if rate in dogs is between 60 & 160/min, called accelerated idioventricular rhythm and NOT usually treated)
113
Q

how is ventricular tachycardia

A

if runs >180/min, symptomatic, multiform R-on-T

lidocaine, magnesium, mexilitine, sotalol, amoidarone

114
Q

what is shown here

A

rapid ventricular tachycardia

115
Q

what are the causes of ventricular tachycardia

A

ventricular myocardial dilation

inflammation

infiltration

fibrosis

trauma

hypoxia

116
Q

what is ventricular escape beat

A

ventricular ectopic following a pause are called escape beats

rescue beat: look for underlying cause of bradycardia

117
Q

what is shown here

A

ventricular escape beat

Module 15 (27 decks)

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