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CPT > 6. Cardiac Arrhythmias > Flashcards

6. Cardiac Arrhythmias Flashcards

1
Q

How do class 1 drugs act?

A

Block Na channels
Marked slowing conduction in tissue
Minor effects on action potential duration

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2
Q

How do class 2 drugs act?

A

Beta blockers
Reduction in effluent of Ca
Diminish phase 4 depolarisation and automaticity

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3
Q

How do class 3 drugs act?

A

Block K channels
Increase action potential duration
Longer refractor period

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4
Q

How do class 4 drugs act?

A

Calcium channel blockers
Decrease inward Ca currents resulting in a decrease of phase 4 spontaneous depolarisation
Affect plateau phase of action potential

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5
Q

What are the effects of Ca channel blockers on slow action potential (SAN, AVN)?

A

Extend slope of phase 0
Increase refractory period
Harder for node to beat again

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6
Q

Where are fast action potentials found?

A

Cardiac and atrial myocytes

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7
Q

Where are slow action potentials found?

A

SA or AV node

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8
Q

What causes a re-entry rhythm?

A
  1. An accessory pathway in heart connecting atrium to ventricle
    - Present only in small populations
    - Wolf-Parkinson-White syndrome (WPW)
  2. Two pathways within AVN
    - causes supraventricular tachycardia (AVNRT)
  3. Scarring
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9
Q

In general, what do drugs work to do in arrhythmias?

A

Reduce abnormal impulse generation
Slow conduction through tissue
Block AV node to terminate some rhythms

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10
Q

Give 2 examples of class 1b agents

A

Lidocaine (IV)

Mexiletine (oral)

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11
Q

What are the effects of class 1B agents on cardiac activity?

A

No change in phase 0 in normal tissue
Action potential duration slight decreased
Increase threshold (Na+)
Decrease phase 0 conduction in fast beating or ischaemic tissue

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12
Q

What are the effects of class 1B agents on ECG?

A

None in normal heart

In fast beating or ishcaemic heart, prolongation of QRS

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13
Q

What are the uses of class 1B agents?

A

Acute - ventricular tachycardia

Not used in atrial arrhythmias or AV junctional arrhythmias

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14
Q

What are the side effects of class 1B drugs?

A 
Less pro arrhythmic than class 1A
Dizziness, drowsiness
Abdominal upset
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15
Q

Name 2 class 1C agents

A 
Flecanide 
Propafenone (used less)
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16
Q

What are the effects of class 1C agents on cardiac activity?

A

Substantially decreased phase 0 (Na+) in normal heart
Decreased automaticity (increased threshold)
Increased action potential duration and increased refractory period

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17
Q

What are the effects of class 1C agents on ECG?

A

Prolonged PR, QRS and QT

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18
Q

What are class 1C agents used for?

A

Wide spectrum
Used for supraventricular arrhythmias (fibrillation and flutter)
Premature ventricular contractions (ectopic beats)
WPW syndrome

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19
Q

What are the side effects of class 1C agents?

A

Pro-arrhythmia and sudden death especially with chronic use and in structural heart disease
Increase ventricular response to supraventricular arrhythmias
CNS and GI effects

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20
Q

Name some class II agents

A

Propranolol
Bisoprolol
Metoprolol
Esmolol (very short acting)

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21
Q

What are the effects of class II agents on cardiac activity?

A

Increase action potential duration and refractory period in AV node to slow AV conduction velocity
Decrease phase 4 depolarisation

22
Q

What are the effects of class II agents on ECG?

A

Prolonged PR

Slower heart rate

23
Q

What are class II agents used for?

A

Treating sinus and catecholamines dependent tachycardia
Converting reentrant arrhythmias at AV node
Protecting the ventricles from high atrial rates in atrial flutter or atrial fibrillation

24
Q

What are the side effects of class II agents?

A

Bronchospasm

Hypotension

25
Q

Name some class III agents

A

Amiodarone

Sotalol

26
Q

What are the cardiac effects of amiodarone?

A 
Increase refractory period and action potential duration
Decrease phase 0 and conduction
Increase threshold
Decrease phase 4
Decrease speed of AV conduction
27
Q

What are the effects of amiodarone on ECG?

A

Prolonged PR, QRS and QT

Decreased heart rate

28
Q

What is amiodarone used for?

A

Effective for most arrhythmias

29
Q

What are the side effects of amiodarone?

A 
Increase with time
Pulmonary fibrosis
Hepatic injury
Increase LDL cholesterol
Thyroid disease
Photosensitivity
Optic neuritis
30
Q

What are the cardiac effects of sotalol?

A

Increased Acton potential duration and refractory period in atrial and ventricular tissue
Slow phase 4
Slow AV conduction

31
Q

What are the ECG effects of sotalol?

A

Prolonged QT

Reduced heart rate

32
Q

What are the uses of sotalol?

A

Supraventricular and ventricular tachycardia

33
Q

What are the side effects of sotalol?

A

Proarrhythmia, fatigue, insomnia

34
Q

Name 2 class IV agents

A

Verapamil

Diltiazem

35
Q

What are the cardiac effects of class IV agents?

A

Slow conduction through AV
Increased refractory period in AV node
Increase slope of phase 4 in SA to slow HR

36
Q

What are the effects on ECG of class IV agents?

A

Prolong PR

May increase or decrease heart rate depending on blood pressure response and baroreflex

37
Q

What are the uses of class IV agents?

A

Control ventricles during supraventricular tachycardia
Convert supraventricular tachycardia
Can be used in asthma patients when beta blockers can’t

38
Q

What are the side effects of class IV agents?

A

Caution when partial AV block present, can get asystole if beta blocker is on board
Caution when hypotension, decreased cardiac output
Some GI problems (constipation)

39
Q

What is the mechanism of adenosine?

A

Natural nucleoside that binds A1 receptors and blocks adenylyl cyclase thus reducing cAMP which in turn activated K+ currents in AV and SA node, causing hyperpolarisation
Therefore leads to decrease in heart rate

40
Q

What are the cardiac effects of adenosine?

A

Slows AV conduction

41
Q

What are the uses of adenosine?

A

Convert re-entrant supraventricular arrhythmias

42
Q

What is the mechanism of ivabradine?

A

Blocks If ion current which is highly expressed in sinus node

43
Q

What are the cardiac effects of ivabradine?

A

Slows the sinus node but does not affect blood pressure

44
Q

What are the side effects of ivabradine?

A

Flashing lights

Teratogenicity not known (avoid in pregnancy)

45
Q

What are the uses of ivabradine?

A

Reduce inappropriate sinus tachycardia

Reduce heart rate in heart failure and angina

46
Q

What is the mechanism of digoxin?

A

Enhances vagal activity

Slows AV conduction and slows HR

47
Q

What are the uses of digoxin?

A

Treatment to reduce ventricular rates in atrial fibrillation and flutter

48
Q

What is the mechanism of atropine?

A

Selective muscarinic antagonist

49
Q

What are the cardiac effects of atropine?

A

Block vagal activity to speed AV conduction and increase HR

50
Q

What are the uses of atropine?

A

Treat vagal bradycardia

CPT (30 decks)

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