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VET 408: Cardio/Respiratory > Cardiac Dysrhythmias > Flashcards

Cardiac Dysrhythmias Flashcards

1
Q

normal ECG (lead II) in dogs

A

P followed by QRS
- stable, unchanging PQ interval
- positive P wave
- net positive, narrow QRS
- positive or negative T wave that does not change

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2
Q

normal ECG in horses (base-apex lead)

A

P followed by QRS
- stable, unchanging PQ interval
- M shaped, biphasic P wave
- net negative, narrow QRS
- positive or negative T wave that does not change

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3
Q

normal sinus rhythm

A

NSR; regular rhythm initiated by the sinus node, conducted normally, and normal rate for the species

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4
Q

sinus bradycardia

A

lower than normal rate

rest is the same as NSR

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5
Q

sinus tachycardia

A

higher than normal rate

rest is the same as NSR

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6
Q

sinus arrhythmia

A

regularly irregular

rate increases and decreases at regular/predictable intervals

respiratory sinus arrhythmia: normal in dogs; increases HR on inspiration, decreases HR on expiration

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7
Q

supraventricular

A

originating from the upper chambers (atria)

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8
Q

junctional

A

originating from the atrioventricular junction (around AV node)

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9
Q

ventricular

A

originating from the lower chambers (ventricles)

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10
Q

what is ECG not sensitive for detecting

A

heart failure/disease resulting in dysfunction

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11
Q

what is paper speed used to measure

A
  1. heart rate
  2. complex/interval duration
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12
Q

standard paper speeds and corresponding values

A

25 mm/s: small box is equal to 0.04 seconds

50 mm/s: small box is equal to 0.02 seconds

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13
Q

what does a faster or slower paper speed correlate to

A

faster paper speed = widens complexes (stretches out X axis)

slower paper speed = narrows complexes (squishes in X axis)

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14
Q

do you use a faster or slower paper speed in cats

A

faster

allows better visualization of complexes due to fast HR

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15
Q

what is calibration used to measure

A

complex size

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16
Q

standard complex sizes

A

10 mm/mV: small box = 0.1 mV

20 mm/mv: small box = 0,05 mV

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17
Q

what causes artifact on ECG

A

poor electrode contact
shivering
purring
electrical interference
respiratory motion
reversed leads
limb movement

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18
Q

do artifacts disrupt the underlying rhythm

A

NO - should still have underlying rhythm

QRS complexes always followed by T wave

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19
Q

what does the P wave correspond to and how does it look on ECG

A

atrial depolarization

SA: small, rounded, positive

LA: M shaped/biphasic

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20
Q

what does the PQ interval correspond to

A

conduction through the slow AV node; includes depolarization of atria and specialized conduction system

should NOT vary between beats

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21
Q

what does the QRS complex correspond to

A

ventricular depolarization

should be NARROW

SA: negative Q, positive R, negative S

LA: negative QRS

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22
Q

what does the T wave correspond to

A

ventricular repolarization

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23
Q

J point

A

end of the R or S wave (if S is present)

starting point of the ST interval

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24
Q

ST segment

A

isoelectric line - no current should be flowing

should be at the same level as the TP interval

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25
Q

TP interval

A

isoelectric line

does not change polarization

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26
Q

what is ST depression

A

when the ST segment is below (more negative) than the TP interval

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27
Q

what is ST elevation

A

when the ST segment is above (more positive) than the TP interval

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28
Q

what does the QT interval correspond to

A

ventricular depolarization + repolarization

slow HR= longer QT interval

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29
Q

what is the risk of prolonged QT interval

A

increased risk of premature depolarizations leading to ventricular fibrillations

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30
Q

mean electrical axis

A

average vector of depolarization

sum of all electrical activity during ventricular depolarization

depends on origin of AP, size of ventricles, speed of electrical conduction

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31
Q

what is the normal QRS MEA in dogs

A

left caudal

most positive leads are lead II and aVF

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32
Q

what is the normal QRS MEA in cats

A

left and right caudal

most positive leads are leads II, III, and aVF

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33
Q

p mitrale

A

wide P wave

caused by LEFT atrial enlargement (takes longer for depolarization to occur

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34
Q

p pulmonale

A

tall P wave

caused by RIGHT atrial enlargement (amplifies depolarization)

35
Q

what causes abnormal P wave morphology

A

non-SA node, supraventricular generated AP (atrial escape beats)

negative P wave

36
Q

what causes unrelated P waves

A

random P waves not associated with QRS complex

caused by miscommunication between atria and ventricles (AV block w/ ventricular escape)

37
Q

what causes absent P waves

A
  1. failure of SA or other nodes to depolarize
  2. ectopic/normal P waves are hiding in the preceding complex
  3. SA node usurped by abnormal rhythm (atrial fibrillation, flutter, ventricular tachycardia)
38
Q

what causes an abnormal PQ interval

A

miscommunication between atrium and ventricle (AV block, ventricular tachycardia)

39
Q

what does a tall QRS complex mean

A

left ventricular enlargement

NORMAL MEA - direction is normal but depolarization is strong (concentric or eccentric hypertrophy)

40
Q

what does a wide QRS complex mean

A

abnormal ventricular depolarization or conduction

(ventricular ectopy, ventricular premature complexes, ventricular escape rhythm, bundle branch block)

41
Q

where does sinus rhythm originate from

A

SA node

42
Q

where does atrial escape beats originate from

A

atrium but non SA node

43
Q

where does junctional escape beats originate from

A

atrioventricular junction

44
Q

where does a L sided ventricular premature complex (VPC) originate from

A

left ventricle (negative QRS)

45
Q

where does a R sided VPC originate from

A

right ventricle (positive QRS)

46
Q

what does an overly narrow QRS complex mean

A

supraventricular origin of AP

47
Q

what are the steps of evaluating cardiac rhythm

A
  1. heart rate
  2. sinus rhythm, yes or no?
  3. ID arrhythmias and conduction abnormalities
48
Q

bradyarrhythmia

A

slow HR that is not initiated by SA node

49
Q

tachyarrhythmia

A

fast HR that is not initiated by SA node

50
Q

how to calculate HR at 25 mm/s paper speed

A

count the number of beats in 30 big boxes

30 big boxes = 6 seconds

10 x # beats = # of beats per minute

51
Q

how to calculate HR at 50 mm/s paper speed

A

count the number of beats in 30 big boxes

30 big boxes = 3 seconds

20 x # beats = # beats per minute

52
Q

how to measure instantaneous heart rate

A

count the number of big boxes between the R-R interval

25 mm/s: 300 / # of big boxes between R-R interval

50 mm/s: 600 / # of big boxes between R-R interval

53
Q

how to evaluate if there is sinus rhythm

A
  1. are there p waves?
  2. are the p waves associated with QRS?
  3. is the p wave MEA normal?
  4. if the rate is variable - does it behave like sinus rhythm (gradually increase/decrease)?
  5. look for respiratory sinus arrhythmia (dogs; wandering pacemaker)
54
Q

wandering pacemaker

A

change in P wave height within one reading caused by change in ANS tone

variable ANS innervation –> rate and location of SA node discharge changes

55
Q

respiratory sinus arrhythmia: inspiration

A

vagal tone predominates –> slows HR, moves SA discharge apically

56
Q

respiratory sinus arrhythmia: expiration

A

vagal tone decreases –> increases HR –> moves SA discharge back to SA node

57
Q

regularly irregular rhythm

A

changes in rhythm occurs at regular intervals

can be NORMAL (dogs - respiratory sinus arrhythmia)

can be ABNORMAL (complete AV block with ventricular escape OR supra-ventricular tachycardia)

58
Q

irregularly irregular rhythm

A

changes in rhythm are patternless/chaotic

always abnormal (ex. atrial fibrillation, ventricular tachycardia)

59
Q

premature complexes

A

early depolarizations, can be ventricular or atrial in orign

60
Q

ventricular premature complexes (VPCs)

A

sinus rhythm followed by a ventricular depolarization

61
Q

bigeminy

A

normal beat followed by abnormal beat

can be ventricular or atrial

62
Q

atrial premature complexes (APCs)

A

sinus rhythm with early atrial depolarizations (supra ventricular)

P waves are hidden in the preceding QRS because the atrium depolarizes too early

63
Q

examples of QRS without a P wave

A

sinus arrest
atrial standstill
atrial fibrillation
ventricular tachycardia
atrial premature complexes

64
Q

sinus arrest

A

SA node fails, causing a period of arrest (isoelectric line) before a non-SA node takes over and slowly spontaneously generates an AP (junctional escape beat)

65
Q

atrial standstill

A

atrial muscle dysfunction causing complete lack of atrial depolarization (no P wave)

66
Q

atrial fibrillation

A

SA node is being usurped by an ectopic rhythm

causes “jiggling baseline” from small fibrillary waves

no p wave, highly variable R-R interval

67
Q

ventricular tachycardia

A

SA node is still firing and atrium is still contracting, but ventricle is driven by ectopic focus

alternates from sinus to arrhythmia and back

68
Q

AV block

A

disruption in the communication between the atria and ventricles

caused by increased vagal tone (AV node disease, drugs, athletic dogs)

69
Q

1st degree AV block

A

prolongation/delay of PQ interval

70
Q

2nd degree (type I) AV block

A

PROGRESSIVE delay of PQ interval until non-conducted P wave

normal sinus rhythm followed by a P without a QRS

can be benign (calm horses at rest)

71
Q

2nd degree (type II) AV block

A

PQ interval is normal up until the non-conducted P wave (NO progressive delay of PQ interval)

NOT benign - caused by conduction system disease

72
Q

low grade 2nd degree type II AV block

A

one non-conducted P wave at a time (2:1 AV conduction)

73
Q

high grade 2nd degree type II AV block

A

> 1 non-conducted P wave at a time (>3:1 AV conduction)

74
Q

3rd degree AV block

A

complete dissociation of atria and ventricles; no conduction across AV node occurs

bundle of his/purkinje have to take over conduction of ventricles (bradyarrhythmia) BUT SA node is still firing at its own pace

causes 2 independent pacemakers to be firing

75
Q

right axis deviation

A

MEA deviates to right cranial or right caudal

caused by: right ventricular enlargement or right bundle branch block

76
Q

right ventricular enlargement

A

MEA becomes right and caudal with NARROW QRS

negative lead I
net positive aVF
narrow QRS

ex. pulmonary stenosis

77
Q

right bundle branch block

A

MEA becomes right and caudal with WIDE QRS

delayed conduction though R bundle branch leading to slow depolarization of RV

78
Q

what causes a wide QRS complex

A

QRS takes longer than normal:

ventricular: VPC or ventricular escape (most wide complexes)

SA/supraventricular: atrial fibrillation, junctional escape beats, bundle branch block

79
Q

left bundle branch block

A

normal MEA (left caudal) with wide R wave in lead II

80
Q

left axis deviation

A

MEA deviates to left cranial (not caudal bc that is normal)

caused by L anterior fascicular block

81
Q

L anterior fascicular block

A

delayed conduction through anterior fascicle of left bundle branch

common in CATS only due to concentric left ventricular hypertrophy

causes positive lead I, negative aVF

82
Q

what causes arrhythmias (in general)

A

disorders of impulse formation
OR
disorders of impulse conduction
OR
both (most often)

83
Q

paroxysmal

A

arrhythmias that last <30 seconds

84
Q

sustained

A

arrhythmias that last >30 seconds

VET 408: Cardio/Respiratory (38 decks)

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