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Y1 - Cardiovascular > Arrhythmias: Anti-Arrhythmic Drugs & Surgery > Flashcards

Arrhythmias: Anti-Arrhythmic Drugs & Surgery Flashcards

1
Q

Name the classification system used for antiarrhythmic drugs

A

Vaughn Williams classification

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2
Q

List the classes of in the Vaughn Williams classification

A

Ia, Ib, Ic
II
III
IV

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3
Q

Give examples of antiarrhythmic drugs that don’t fit into the Vaughn Williams classification

A

Digoxin

Adenosine

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4
Q

What is the target of class Ia drugs?

Describe its action

A

Voltage gated Na+ channel

Associate with and dissociate from Na+ channels at a moderate rate

Slow rate of rise of AP and prolong refractory period

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5
Q

What is the target of class Ib drugs?

Describe its action

A

Voltage gated Na+ channel

Rapidly associate with and dissociate from Na+ channels

Prevent premature beats

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6
Q

What is the target of class Ic drugs?

Describe its action

A

Voltage gated Na+ channel

Slowly associate with and dissociate from Na+ channels

Depress conduction
-ve inotropes

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7
Q

What is the target of class II drugs?

Describe its action

A

β - adrenoceptor (antagonists)

Decrease SA and AV node depolarization rates

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8
Q

What is the target of class III drugs?

Describe its action

A

Voltage-activated K+ channels (& some others)

Prolong phase 3 duration

(class III act on phase 3)

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9
Q

What is the target of class IV drugs?

Describe its action

A

Voltage-activated Ca2+ channels

Slow conduction in SA and AV nodes

Less Ca2+ influx during phase 2

  • ->
  • ve inotropic effect
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10
Q

Which classes of antiarrhythmics act on the atria?

A

Ic, III

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11
Q

Which classes of antiarrhythmics act on the ventricles?

A

Ia, Ib, II

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12
Q

Which classes of antiarrhythmics act on the AV node?

A

II, IV

adenosine, digoxin

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13
Q

Which classes of antiarrhythmics act on the atria and ventricles, and AV accessory pathways?

A

Ia, Ic

Amiodarone, sotalol

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14
Q

What phase of the action potential do class I drugs effect?

A

Phase 0 in fast response cells

as phase 0 is due to Na+

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15
Q

What phase of the action potential do class II drugs effect?

A

Phase 0 in slow response cells

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16
Q

What phase of the action potential do class III drugs effect?

A

Phase 3

as phase 3 is due to K+

17
Q

What phase of the action potential do class IV drugs effect?

A

Phase 2 in fast response cells
Phase 0 in slow response cells

(as these are due to Ca2+)

18
Q

In what states of the voltage dependant Na+ channel do class 1 drugs bind?

  • Open
  • Inactivated
  • Resting
A

Class 1 drugs bind to voltage dependant Na+ channels in their open and inactivated states

They dissociate during the resting state

19
Q

Do class 1 drugs preferentially bind to myocytes with higher or lower firing frequencies?

A

They bind preferentially to areas of high firing frequency

20
Q

Why do class I drugs preferentially bind to ischaemic tissue and ectopic foci?

A 
Ischaemia
-->
longer action potentials
-->
less time for Na+ channel in its resting state
-->
class I drugs are bound for longer
-->
Higher affinity for class I

(can be the same logic for ectopic foci)

21
Q

What is radiofrequency catheter ablation?

What does it target?

What can it be done straight after?

A

Ablation of cardiac tissue with catheter

Can target part of a reentrant circuit or a ectopic foci

Can be done in the same procedure as an electrophysiological study

22
Q

Describe a single chamber pacemaker

A

Only paces the right atria or right ventricle

23
Q

Describe a dual chamber pacemaker

A

Paces the right atrium and right ventricle

  • used for AV node disease
24
Q

Describe an implantable cardioverter defibrillator (ICD)

A

Does:

  • Pacing
  • Cardioversion
  • Defibrillation

Can get dual chamber ICDs

25
Q

What is the difference between an ICD and a pacemaker?

A

ICD can shock you back into rhythm

Pacemaker can’t

26
Q

What does a pacemaker do?

A

Paces the heart rate

27
Q

Describe direct current cardioversion (DCCV)

A

DC shocks via external electrodes

Need sedation/analgesia

Used during fibrillation to restore NSR

(antiarrhythmic drugs can be given at the same time)

Y1 - Cardiovascular (19 decks)

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