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Medicine, Year 2, Block 13 (Cardiorespiratory Disease) > Pharmacology of Rhythm Control > Flashcards

Pharmacology of Rhythm Control Flashcards

1
Q

What is the resting potential of a Cardiac Action Potential?

A

-90mV

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2
Q

Explain what happens in Phase 4 of the Cardiac Action Potential

A

The potential is -90mV. Na+ and Ca2+ channels are closed, however K+ rectifier channels are open

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3
Q

Explain what happens in Phase 0 of the Cardiac Action Potential

A

Rapid depolarisation. Na+ channels open, due to influx of Na+ entering the cell

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4
Q

Explain what happens in Phase 1 of the Cardiac Action Potential

A

Rapid repolarisation, due to closure of Na+ channels and transient channels opening. K+ moves out

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5
Q

Explain what happens in Phase 2 of the Cardiac Action Potential

A

Delay repolarisation. L-type Calcium channels open and Ca2+ moves in. K+ still moves out

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6
Q

Explain what happens in Phase 3 of the Cardiac Action Potential

A

Second repolarisation. K+ continues to move out, but Ca+ channels now close

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7
Q

What is the intrinsic firing rate of the Sinoatrial node?

A

105 bpm

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8
Q

At rest, how is the SAN influenced?

A

At rest, parasympathetic and sympathetic feed is active, but vagal inhibition dominates

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9
Q

What is the intrinsic firing rate of the Bundle of His?

A

40 bpm

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10
Q

What is the speed of conduction in the Atria?`

A

1 m/s

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11
Q

What is the speed of conduction in the AVN?

A

0.05 m/s

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12
Q

What is the speed of conduction in the Bundle of His?

A

2 m/s

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13
Q

What is the speed of condunction in the Purkinje fibres?

A

4 m/s

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14
Q

What is the speed of condunction of the Ventricles?

A

1 m/s

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15
Q

What does ARP stand for? What does it mean?

A

Absolute Refractory Period, a period where the heart cannot be excited

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16
Q

What does RRP stand for? What does it mean?

A

Relative Refractory Period, a period where the heart could be vulnerable to excitation

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17
Q

Outline the types of AV block

A
  • First degree block
  • Second degree, Mobitz Type 1 block (Wenklebach)
  • Second degree, Mobitz Type 2 block
  • Third degree block
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18
Q

What are the symptoms of Type 1 AV Block?

A

Asymptomatic

19
Q

What is First degree AV Block defined as?

A

Having a PR interval greater than 0.2 s

20
Q

Outline what Second degree, Mobitz Type 1 AV Block is defined as?

A

Progressive PR interval until the P wave fails to conduct

21
Q

Outline what Second degree, Mobitz Type 2 AV Block is defined as?

A

Sinus rhythm, normal PR interval but P wave is not always followed by QRS complex

22
Q

Outline what Third degree AV Block is defined as?

A

Normal P wave, unrelated to QRS. Normal QRS, unrelated to P wave

23
Q

What are some symptoms of Type 2 and Type 3 AV Block?

A
  • Fainting
  • Dizzines
  • Fatigue
  • SOB
  • Chest pain
24
Q

What is a differential diagnosis for SVT?

A

Atrial Fibrillation with 2:1 AV conduction

25
Q

What is the treatment for Bradycardia? What is its mechanism of action?

A

Atropine, which increases HR by inhibiting PNS. mAChR antagonist, hence increases firing of SAN / AVN

26
Q

What is the dosage of Atropine for treating Bradycardia?

A

500 mg IV every 3-5mins

27
Q

Some patients may induce Bradycardia by overdosing on Beta blockers or Calcium channel blockers. What is the antidote?

A

Glucagon

28
Q

Some patients may induce Bradycardia by overdosing on Digoxin. What is the antidote?

A

Digoxin-specific antibody

29
Q

What is the mechanism of action of Theophylline?

A

Adenosine receptor antagonist

30
Q

What do Class I anti-arrhythmic drugs target? What stage of the Cardiac Action Potential do they inhibit?

A

Class I inhibit Na+ channels, targeting Phase 0 of the Cardiac AP

31
Q

What do Class III anti-arrhythmic drugs target? What stage of the Cardiac Action Potential do they inhibit?

A

Class III inhibit K+ channels, targeting Phase 3 of the Cardiac AP

32
Q

What do Class IV anti-arrhythmic drugs target? What stage of the Cardiac Action Potential do they inhibit?

A

Class IV inhibit L-type Ca2+ channels, targeting Phase 2 of the Cardiac AP

33
Q

Give an example of a Class Ia Anti-arrhythmic drug. What is its effect on the Action Potential?

A

Dyspyramide

Increases duration of AP

34
Q

Give an example of a Class Ib Anti-arrhythmic drug. What is its effect on the Action Potential?

A

Lidocaine

Decreases duration of AP

35
Q

Give an example of a Class Ic Anti-arrhythmic drug. What is its effect on the Action Potential

A

Flecainide

No effect on AP

36
Q

What do Class II Anti-arrhythmic drugs inhibit? What is the electrophysiological action?

A

B-adrenergic receptor blocker, preventing SAN conduction

37
Q

Give two examples of Class II Anti-arrhythmic drugs

A

Atenolol

Sotalol

38
Q

Give two examples of Class III Anti-arrhythmic drugs. What is its electrophysiological action?

A

Amiodarone
Sotalol

Widens duration of AP

39
Q

Give two examples of Class IV Anti-arrhythmic drugs. What is its electrophysiological action?

A

Verapamil
Dilitazem

Blocks SAN / AVN conduction

40
Q

What is the mechanism of Adenosine? What is its Electrophysiological function? What can it be used to treat?

A

K+ channel AGONIST
Blocks SAN / AVN

Used to treat SVT

41
Q

What is the mechanism of action of Digoxin?

A

Na+/K+ ATPase inhibitor. Leads to Na+ intracellular increase, leading to Ca2+ increase. This facilitates increased Ionotrophy (force of contraction) and reduced chronotropy (heart rate)

42
Q

What class of Anti-arrhythmic drugs does Amiodarone belong to?

A

Class I, II, III

43
Q

What class of Anti-arrhythmic drugs does Sotalol belong to?

A

Class II, III

44
Q

What are two side effects of Amiodarone?

A

Blue-grey skin discoloration

Skin hypersensitivity

Medicine, Year 2, Block 13 (Cardiorespiratory Disease) (20 decks)

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