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Cardio > Arrhythmias Overview > Flashcards

Arrhythmias Overview Flashcards

1
Q

What are the two basic properties of the heart?

A
  1. Mechanical

2. Electrical

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2
Q

What electrolytes are found in higher concentrations outside of the myocyte?

A

Calcium and sodium

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3
Q

What electrolyte is found in a higher concentration inside the myocyte?

A

Potassium

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4
Q

How many phases are in a normal myocyte action potential?

A

5 phases

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5
Q

How many phases are in an SA action potential?

A

3 phases

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6
Q

Describe normal electrical conduction through the heart

A
  1. SA node fires a signal
  2. Travels to AV node
  3. AV node to bundle of His
  4. Splits to left and right bundle branches
  5. Purkinje fibers
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7
Q

What influences the SA node?

A

autonomic nervous system

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8
Q

Why does conduction slow at the AV node?

A

To allow the atrial tissue to completely depolarize, contract, and expel blood into the ventricles, and to limit impulses that can activate the ventricle

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9
Q

What happens to the electrical signal after the Purkinje fibers?

A

It reaches recently excited (refractory tissue) and dies out

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10
Q

What does the p-wave represent on an EKG?

A

Atrial depolarization in response to firing of the SA node

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11
Q

What does the QRS complex represent on an EKG?

A

Depolarization of ventricles

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12
Q

What does the t-wave represent on an EKG?

A

Ventricular repolarization

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13
Q

What does the PR interval represent on an EKG?

A

The delay of the AV node to allow filling of the ventricles

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14
Q

What does the ST segment represent on an EKG?

A

The beginning of ventricular repolarization (should be flat)

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15
Q

How long is a normal PR interval on an EKG?

A

120-200 msec (0.12-0.2 sec)

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16
Q

What is a longer PR interval indicative of?

A

Heart block

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17
Q

What is a normal QT interval on an EKG?

A

200-400 msec (0.2-0.4 sec)

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18
Q

What is a higher QT interval indicative of?

A

A greater risk of ventricular arrhythmias

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19
Q

What are the two types of abnormal conductions?

A
  1. Automatic tachycardias

2. Re-entrant tachycardias

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20
Q

Describe the mechanism of an automatic tachycardia

A

A random cell takes over and beats faster than the SA and creates and ectopic beat

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21
Q

When does an automatic tachycardia usually occur?

A

When there is a blockage in the AV node

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22
Q

What are some common causes of an automatic tachycardia?

A
  1. Digitalis glycosides
  2. Catecholamines
  3. Electrolyte abnormalities
  4. Myocardial fiber stretch
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23
Q

Describe the mechanism of a Re-entrant tachycardia

A

Conducting pathway is stimulated prematurely by a previously conducted action potential leading to rapid cyclical reactivation

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24
Q

What are examples of Re-entrant tachycardia?

A

Atrial fibrillation, atrial flutter, AV nodal or AV re-entrant tachycardia, or recurrent VT

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25
Q

How are antiarrhythmic drugs classified?

A

By where they work in the action potential

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26
Q

What drug is in class 1a?

A

Procainamide

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27
Q

How does procainamide work?

A

It blocks sodium in and blocks potassium out, which lowers the conduction velocity and increases the refractory/repolarization period

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28
Q

What are the side effects associated with procainamide?

A
  1. Drug-induced lupus
  2. Agranulocytosis
  3. QT prolongation
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29
Q

In what population should you monitor procainamide closely?

A

In patients with renal disease

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30
Q

What drug is in class 1b?

A

Lidocaine (Xylocaine)

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31
Q

What does lidocaine do?

A

It has very little effect on sodium and increases potassium efflux which shortens the refractory period

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32
Q

What are the side effects associated with lidocaine?

A
  1. Hypotension

2. Seizures at high doses

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33
Q

What is the formulation of lidocaine?

A

IV only

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34
Q

What drug is in class 1c?

A

Propafenone

35
Q

What does propafenone do?

A

It block sodium entry for a long time and has no effect on potassium which decreases the conduction velocity

36
Q

What are class 1a drugs used for?

A

Afib and VT

37
Q

What are class 1b drugs used for?

A

VF or VT

38
Q

What are class 1c drugs used for?

A

VT or PSVT

39
Q

What are the class 2 drugs?

A

Beta-blockers

40
Q

What do you give a patient with tachycardia after surgery?

A

Beta-blocker

41
Q

What is the antiarrhythmic mechanism of a beta-blocker?

A

It has anti-adrenergic actions so it works against the SA and AV nodes and indirectly effects calcium influx

42
Q

What effects do beta-blockers have on the conduction velocity and refractory period?

A

They decrease conduction velocity and shorten refractory period

43
Q

What are the class 3 drugs?

A
  1. Dofetilide
  2. Sotalol
  3. Dronedarone
  4. Amiodarone
44
Q

What do class 3 drugs do?

A

They have no effect on sodium and block outward flow of potassium which prolongs the refractory period

45
Q

What is the danger of having too much potassium blockage?

A

It can lead to more arrhythmias

46
Q

What is dofetilide used for?

A

To convert afib to a normal sinus rhythm and maintenance afterwards

47
Q

What are the common side effects of dofetilide?

A

Heart attack, QT prolongation, and bradycardia

48
Q

What is the the major interaction with dofetilide?

A

3A4 substrate (black box warning)

49
Q

What are the clinical pearls of dofetilide?

A
  1. renal dose adjustment

2. PharmD/MD must be registered to use

50
Q

What is propafenone used for?

A

VT or PSVT

51
Q

What are the major adverse effects of propafenone?

A
  1. Neutropenia
  2. Agranulocytosis
  3. New or worsened arrhythmias
  4. Heart block
  5. QT prolongation
52
Q

What are the interactions with propafenone?

A

1A2, 2D6, and 3A4 substrate P glycoprotein inhibitor

53
Q

What are the clinical pearls of propafenone?

A
  1. PO only
  2. renal and hepatic dose adjustment
  3. Worsens HF
54
Q

What is sotalol used for?

A

VT, afib, and aflutter

55
Q

What are the common adverse effects of sotalol?

A
  1. QT prolongation
  2. bradycardia
  3. N/V/D
  4. bronchospasms
56
Q

What are the interactions with sotalol?

A

Low potassium and HF patients

57
Q

What is the one clinical pearl of sotalol?

A

It has a renal adjustment

58
Q

What is dronedarone used for?

A

afib and aflutter

59
Q

What are the common adverse effects of dronedarone?

A
  1. Liver failure
  2. QT prolongation
  3. HF
  4. Heart block
60
Q

What are the interaction with dronedarone?

A
  1. 3A4 substrate (black box warning)
  2. Digoxin - decrease dose by 50%
  3. Warfarin - start dose at 2.5 mg
61
Q

What is the clinical pearl associated with dronedarone?

A
  1. You must stop all class one and three agents first

2. Similar to amiodarone without iodine

62
Q

What is the most popular antiarrhythmic?

A

Amiodarone

63
Q

What characteristics of the the Vaughan Williams classes does amiodarone have?

A

Some of all classes. It blocks sodium and potassium, it has noncompetitive, nonselective beta-blocker actions, and has a small degree of calcium antagonist activity

64
Q

What is the initial action of amiodarone?

A

Beta-blockade

65
Q

What is different about amiodarone’s pharmacokinetics?

A

It has an extremely long half life of 15 to 100 days

66
Q

What is amiodarone used for?

A

afib, aflutter, VT, VF, and PSVT

67
Q

What are the interactions with amiodarone?

A
  1. inhibits P-glycoprotein and most CYP-450 enzymes
  2. Digoxin
  3. Warfarin
68
Q

What are the side effects of amiodarone?

A
  1. Pulmonary fibrosis
  2. Hypothyroidism
  3. Hyperthyroidism
  4. Optic neuritis
  5. Increased LFTs
  6. Bradycardia/HB
  7. Tremors, ataxia, peripheral neuropathy
  8. Photosensitivity/blue-gray skin
69
Q

What do you do in pulmonary fibrosis?

A

Discontinue amiodarone and start a corticosteroid

70
Q

What do you do in hypothyroidism?

A

Start a thyroid hormone supplement

71
Q

What do you do in hyperthyroidism?

A

Start an antithyroid drug

72
Q

What do you do in optic neuritis?

A

Stop amiodarone

73
Q

What do you do in increased LFTs?

A

consider lowering amiodarone dose or discontinue if LFTs> 3x normal

74
Q

What do you do in bradycardia/HB?

A

Lower the dose of amiodarone or discontinue if severe

75
Q

What do you do in tremors, ataxia, or peripheral neuropathy?

A

Lower the dose of amiodarone or discontinue if severe

76
Q

What do you do in photosensitivity/blue-gray skin discoloration?

A

wear sunblock outside

77
Q

What are your class 4 drugs?

A

Calcium channel blockers

78
Q

What do class 4 drugs do?

A

slow down conduction velocity and prolong repolarization

79
Q

What are class 4 drugs used for?

A

SA/AV node automatic or reentrant tachycardias

80
Q

What is adenosine used for?

A

PSVT

81
Q

What are the common side effects of adenosine?

A
  1. flushing
  2. chest burning
  3. bronchospasms
82
Q

What are the interactions with adenosine?

A

None because the half life is less than 10 seconds

83
Q

What are the clinical pearls of adenosine?

A
  1. IV only

2. Will induce asystole momentarily after administration

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