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RUSVM SAM 1 > Arrhythmias 1 > Flashcards

Arrhythmias 1 Flashcards

1
Q

Why do arrhythmias occur?

A

The heart is diseased

  • atria or ventricular myocardium
  • conducting system
  • cardiac blood supply

Extra-cardiac Disease affecting hearts electrical activity or cardiac blood supply

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2
Q

What are the mechanisms of arrhythmias?

A

Disturbances of impulse formation (excitability)

Disorders of impulse transmission (conduction)

Complex: disorders of both impulse formation and conduction

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3
Q

What ions are responsible for impulses in the heart?

A

Potassium
Calcium
Sodium
Magnesium

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4
Q

What happens is excitability is increase and intermittent?

A

Premature heart beats

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5
Q

What occurs if cardiac excitability is increased and sustained?

A

Tachycardia

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6
Q

What occurs is excitability is intermittently decreased?

A

Sinus pause (lack of sinus compels)

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7
Q

What occurs is there is a decreased and sustained excitability ?

A

Bradycardia or asystole

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8
Q

What are the 3 classifications of disturbances of impulse formation?

A
  1. Sinus
  2. Supraventricular (atria/AV node/junction / SA node)
  3. Ventricular
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9
Q

What do you call a sinus rhythm with an abnormally low heart rate?

A

Sinus bradycardia

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10
Q

What are the causes of sinus bradycardia ?

A

Primary - sinus node dysfunction / sick sinus syndrome

Secondary - increased vagal (PSNS) tone

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11
Q

What are pathologic causes of high vagal tone?

A

Respiratory/intrathoracic disease

GI disease

Neurological disease (Increase ICP)

Ophthalmic disease (increase IOP)

Drugs/deep anestheric plane

Toxins

Hypothermia

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12
Q

What are non-pathologic causes of high vagal tone?

A

Sleep/rest
Athleticism
Brachycephalic

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13
Q

What do you call a sinus rhythm with abnormally high heart rate ?

A

Sinus tachycardia

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14
Q

What are causes of sinus tachycardia?

A

Primary- sinus node dysfunction/ sick sinus syndrome

Secondary - increased sympathetic tone

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15
Q

What are causes of high sympathetic tone?

A 
Hypotension 
Hypoxia 
Anemia 
Pain 
Fear/excitement 
Drugs/toxins
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16
Q

What is a supraventricular premature complex?

A

Premature depolarization generated by an ectopic impulse located ABOVE the ventricles

  • atrial -most common
  • AV node/junction
  • SA node
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17
Q

ECG

RR interval between sinus beats is regular, with shortened RR intervals.
There is a P before evert QRS
P between the short RR intervals has a different morphology than the sinus beats
QRS are narrow and same morphology as sinus beats

Interpretation??

A

Supreventricular premature complexes

-the short RR intervals are due to ectopic beats with P’ having different appearance than the P for the sinus beat

QRS have same morphology because there is normal conduction following the AV node

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18
Q

What are causes of a supraventricular premature complex?

A

Atrial dilation associated with structural heart disease
Atrial tumor
Various systemic and metabolic diseases
Drugs

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19
Q

What is a supraventricular tachycardia?

A

Any pathologic tachycardia originating above the ventricles

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20
Q

What are the types of SVT?

A 
Atrial 
AV nodal 
Junctional 
SA nodal 
Bypass tract
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21
Q

ECG

> 3 consecutive SVPC with abnormally high rate
P’ instead of Pwaves

Interpretation?

A

Supraventricular tachycardia

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22
Q

T/F: supraventricular tachycardias usually have an irregular rhythm

A

False

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23
Q

What is atrial fibrillation?

A

Chaotic and rapid impulses from the atria

-large surface area is required for AF

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24
Q

ECG

Irregularly irregular RR intervals
No Pwaves
Fibrillation waves
QRS are narrow

Interpretation ??

A

Atrial fibrillation

-fibrillation waves are just partial depolarizations of the atria, not a full wave

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25
Q

T/F: in Afib, heart rate is often fast, but can be normal or slow

A

True

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26
Q

Atrial fibrillation in dogs and cats is usually secondary to ???

A

atrial dilation associated with structural heart disease

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27
Q

What dogs can get a lone (primary) Afib, where there is no structural heart disease

A

Giant and large-breed dogs

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28
Q

What is atrial flutter?

A

Organized and rapid atrial impulse

  • not as fast as Afib
  • waves are uniform
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29
Q

ECG

No P waves, instead waves have uniform and “saw tooth” appearance
No return to baseline
QRS are narrow
RR can be regular/irregular

Interpretation?

A

Atrial flutter

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30
Q

T/F: atrial flutter and Atrial fibrillation usually have sustained (continuous) rhythms

A

True

31
Q

How can you differentiate a sinus tachycardia from a SVT/A flutter?

A

ST is rarely >220bpm in dog, or >280bpm in cats

Any medial reason to have ST?
-history, PE, BP, minimum database

Vagal maneuver to slow rate —> visualization of P/P’/flutter waves

SVT and A flutter and due to pathological abnormalities in the heart
ST is a normal physiological response to something external to the heart

32
Q

What is ventricular premature complex?

A

Premature depolarization generated by an ectopic focus located in the ventricular tissue (ie past the bundle branches)

33
Q

What is the most common cause of ventricular premature complexes?

A

Cardiomyopathies

34
Q

What are the non-cardiac causes of ventricular premature complex?

A

Abdominal tumors (splenic or hepatic)

Gastric dilatation-volvulus

Hypokalemia

Acidosis

Anemia

Hypoxemia

Trauma

Semis

Hypovolemia

Drugs/toxins

35
Q

ECG

Premature QRS
Wide QRS, can be positive, negative, or biphasic
QRS is not associated with a P wave
Followed by a pause

A

Ventricular premature complex

36
Q

Where are QRS complexes in VPC wide?

A

Impulse travels by muscle, no conduction system —> takes more time —> wide QRS

37
Q

What is a ventricular tachycardia?

A

Tachycardia originating from the ventricle

38
Q

ECG

> 3 consecutive VPCs with an abnormally high rate
Regular, fast, wide QRS

A

Ventricular tachycardia

39
Q

What conditions can make a wide and fast QRS but that is not ventricular tachycardia ?? How can you tell them apart from VT?

A

ST + ventricular enlargement /BBB

SVT + ventricular enlargement / BBB

Not VT because PR interval is normal and consistent —> AV associated
VT—> AV disassociation

40
Q

What is ventricular fibrillaiton?

A

Chaotic/disorganized and rapid ventricular impulses

—> ventricles quiver instead of contract ==> no CO or BP

41
Q

ECG

Erratic waves of variable morphology
No pattern
Incomplete waves

A

Ventricular fibrillation
—>fatal rhythm
—>ventricular tachycardia can deteriorate into VF

42
Q

What is an accelerated idioventricular rhythm ?

A

Has all the same features of a ventricular tachycardia but it is not fast

Usually a stable rhythm that does not require therapy

43
Q

What are the three types of disorders of impulse conduction?

A

AV block

Bundle branch block

Atrial standstill

44
Q

What is first degree AV block?

A

Conduction in the AV node is delayed

45
Q

ECG

Prolonged PR interval
PR interval is consistent
QRS is normal

A

First degree AV block

46
Q

What are causes of first degree AV block?

A

High vagal tone (most common)

Drugs/toxin (digoxin)

47
Q

T/F: first degree AV block is not hemodynamically significant

A

True

48
Q

What is second degree AV block?

A

Conduction through AV node is stopped but only transiently

49
Q

ECG

Some P waves do not have a QRS after them
QRS have a normal appearance

A

Second degree AV block

50
Q

What is a Mobitz type I AV block

A

Prolongation of the PR interval prior to the block

51
Q

What is a Mobitz type II AV block

A

No prolongation of PR interval prior to block

Low grade —> more waves are conducted than not

High grade —> more waves are block than are conduction —> bradycardia

52
Q

What is third-degree AV block ?

A

Conduction through the AV node is stopped permanently

An impulse from the atria never makes it to ventricle —> QRS are junctional escape complexes

53
Q

ECG

P occurs without QRS
PR intervals are not consisted
ORS are preceded by a pause
Heart rate is low

A

Third degree AV block

54
Q

What are causes of first degree and Mobitz type I second degree AV block?

A

High vagal tone!

Drugs (digoxin, A2 agonsits)

55
Q

What are causes of Mobitz type II second degree AV block and third degree>

A

Structural disease of AV node (most common)
Eg. Degeneration, fibrosis inflammation, or neoplasia

Hyperkalemia
Drugs

56
Q

What is a bundle branch block?

A

Delays in the conduction/lack of conduction in the left and/or right bundle branch

57
Q

What is the appearance of QRS in BBB?

A

Wide

Dog > 70ms
Cat >40ms

58
Q

Is a right BBB, the QRS is __________ in lead II

A

Negative

59
Q

In the left BBB, QRS is _________ in lead II

A

Positive

60
Q

T/F: Bundle branch blocks have AV association, where ventricular rhythms do not

A

True

61
Q

What is the cause of a left BBB?

A

Structural heart disease (cardiomyopathy )

62
Q

What is the cause of a right bundle branch block?

A

Idiopathic in some dogs

Structural heart disease

63
Q

Transient BBB’s can occur with??

A

Fast sinus tachycardia or SVT

64
Q

What is atrial standstill?

A

Absence of atrial depolarization

65
Q

ECG

No P waves (no flutter or fibrillation )
QRS is normal
Bradycardia
Regular rhythm

A

Atrial standstill

—> escape rhythm depolarizes ventricles

66
Q

What are causes of atrial standstill?

A

Hyperkalemia
Atrial myopathy
Neuromyopathy (springer spaniel)

67
Q

What is sick sinus syndrome?

A

Complex disturbance of conductive tissues resulting in

  • sinus bradycardia / sinus arrest
  • supraventricular or ventricular premature complexes (or SVT/VT)
  • first or second degree AV block
68
Q

What causes sick sinus syndrome ?

A

SA node cells are replaced by fibrous/fibrofatty tissue- idiopathic

69
Q

What breeds are predisposed to SSS?

A

Miniature schnauzer
West Highland White terrier
Dashunds
Cocker Spaniel

70
Q

What abnormalities will you see with hypokalemia?

A

Prolong repolarization
-VPC/APC

Lowers the resting membrane potential

71
Q

What abnormalities would you see with MILD hyperkalemia ??

A

Shortened repolarization (Twave abnormalities are insensitive and non-specific)

72
Q

What abnormalities would you see with a MODERATE hyperkalemia ?

A

Prolonged transmission velocity (wide QRS complexes)

73
Q

What abnormalities do you see with SEVERE hyperkalemia ?

A

Prolonged PR interval or absent P wave

Ventricular fibrillation

Pulseless electrical activity/electromechanical dissociation (PEA/EMD)

74
Q

What electrolyte in a major regulator in enzymatic reactions of potassium?

A

Mg

RUSVM SAM 1 (26 decks)

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