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

Pharmacology of Rhythm Control Flashcards

(44 cards)

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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?

19
Q

What is First degree AV Block defined as?

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A

Having a PR interval greater than 0.2 s

20
Q

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

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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?

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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?

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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?

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

What is a differential diagnosis for SVT?

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A

Atrial Fibrillation with 2:1 AV conduction

25
What is the treatment for Bradycardia? What is its mechanism of action?
Atropine, which increases HR by inhibiting PNS. mAChR antagonist, hence increases firing of SAN / AVN
26
What is the dosage of Atropine for treating Bradycardia?
500 mg IV every 3-5mins
27
Some patients may induce Bradycardia by overdosing on Beta blockers or Calcium channel blockers. What is the antidote?
Glucagon
28
Some patients may induce Bradycardia by overdosing on Digoxin. What is the antidote?
Digoxin-specific antibody
29
What is the mechanism of action of Theophylline?
Adenosine receptor antagonist
30
What do Class I anti-arrhythmic drugs target? What stage of the Cardiac Action Potential do they inhibit?
Class I inhibit Na+ channels, targeting Phase 0 of the Cardiac AP
31
What do Class III anti-arrhythmic drugs target? What stage of the Cardiac Action Potential do they inhibit?
Class III inhibit K+ channels, targeting Phase 3 of the Cardiac AP
32
What do Class IV anti-arrhythmic drugs target? What stage of the Cardiac Action Potential do they inhibit?
Class IV inhibit L-type Ca2+ channels, targeting Phase 2 of the Cardiac AP
33
Give an example of a Class Ia Anti-arrhythmic drug. What is its effect on the Action Potential?
Dyspyramide | Increases duration of AP
34
Give an example of a Class Ib Anti-arrhythmic drug. What is its effect on the Action Potential?
Lidocaine | Decreases duration of AP
35
Give an example of a Class Ic Anti-arrhythmic drug. What is its effect on the Action Potential
Flecainide | No effect on AP
36
What do Class II Anti-arrhythmic drugs inhibit? What is the electrophysiological action?
B-adrenergic receptor blocker, preventing SAN conduction
37
Give two examples of Class II Anti-arrhythmic drugs
Atenolol | Sotalol
38
Give two examples of Class III Anti-arrhythmic drugs. What is its electrophysiological action?
Amiodarone Sotalol Widens duration of AP
39
Give two examples of Class IV Anti-arrhythmic drugs. What is its electrophysiological action?
Verapamil Dilitazem Blocks SAN / AVN conduction
40
What is the mechanism of Adenosine? What is its Electrophysiological function? What can it be used to treat?
K+ channel AGONIST Blocks SAN / AVN Used to treat SVT
41
What is the mechanism of action of Digoxin?
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
What class of Anti-arrhythmic drugs does Amiodarone belong to?
Class I, II, III
43
What class of Anti-arrhythmic drugs does Sotalol belong to?
Class II, III
44
What are two side effects of Amiodarone?
Blue-grey skin discoloration | Skin hypersensitivity

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

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