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Anti-arrhythmics Flashcards

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1
Q

What is the distribution of ions inside and outside a cardiac myocyte?

A

Na higher outside
Ca higher outside
K higher inside

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2
Q

What are the diff ends phases of the cardiac action potential?

A

Phase 0 - depolarisation, Na influx

Phase 1 - slight repolarisarion, K+ and Cl- out

Phase 2 - plateau - Ca in, K out

Phase 3 - repolarisarion - K out

Phase 4 - resting membrane potential

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3
Q

Why arrhythmias cause the heart to contract too quickly?

A

AF
AV re-entry tachycardia
Ventricular tachycardia
Torsades de Pointes

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4
Q

What arrhythmias can cause the heart to be too slow?

A

Sinus bradycardia

First to third degree heart block

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5
Q

What can cause cardiac arrhythmias (at more of a cellular level, not clinical conditions)

A

Enhanced automaticity

Delayed after-depolarisations

Early after-depolarisations

Re-entry circuits

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6
Q

What are class I anti-arrhythmic drugs?

A

Sodium channel blockers

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7
Q

What are class II anti-arrhythmic drugs?

A

Beta blockers

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8
Q

What are class III anti-arrhythmic drugs?

A

Potassium channel blockers

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9
Q

What are class IV anti-arrhythmic drugs?

A

Calcium channel blockers

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10
Q

What is the path of the action potential in the heart?

A 
SA node 
Across atria
AV node 
Bundle of His
Left and right bundle branches
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11
Q

Difference between class Ia, b and c drugs?

A

1a - intermediate dissociation
1b - rapid dissociation
1c - slow dissociation

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12
Q

Give an example of class 1a

A

Quinidine

Procainamide

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13
Q

What is the effect of 1a drugs?

A

Slow phase 0 of action potential in ventricular muscle fibres
Increase the refractory period/repolarisation
Decrease automaticity
Increase the threshold

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14
Q

What is automaticity?

A

A cell’s ability to spontaneously generate an electrical impulse

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15
Q

What changes are seen on an ECG with 1a drugs?

A

Increase QRS
Increase PR interval
Increase QT interval

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16
Q

Uses of 1a drugs?

A

Quinidine - maintains a sinus rhythm in AF and flutter, prevents recurrent tachycardia and fibrillation

Procainamide - used for acute treatment of supraventricular and ventricular arrhythmias

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17
Q

ADRs of 1a drugs?

A 
Hypotension
Reduced CO
Pro-arrhythmia eg Torsades de Pointes 
GI effects 
Dizziness, confusion, insomnia, seizure 
Lupus-like syndrome
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18
Q

How do 1b drugs work?

A

Bind to inactive sodium channels in phase 0 and dissociate rapidly in time for next action potential

Stop a premature beat because the sodium channels would still be blocked but have no effect in normal tissue

Increase the threshold for action potential

Use-dependent

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19
Q

Effects on ECG of class 1b?

A

None in normal tissue

Increase QRS complex in fast-beating or ischaemic (depolarised) tissue

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20
Q

Name some class 1b drugs

A

Lidocaine

Mexilatine
Phenytoin

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21
Q

Uses of class 1b?

A

Prevent ventricular tachycardia and fibrillation following an MI
(IV lidocaine given)

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22
Q

ADRs of 1b? (Lidocaine)

A

Less pro-arrhythmic than 1a due to less effect on QT

CNS - drowsiness and dizziness

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23
Q

How do class 1c drugs work?

A

Slow dissociation with sodium channels so reach a steady state of block

Decreases automaticity and increases threshold

Increases action potential duration and increases refractory period

Decreases phase 0 in normal tissue

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24
Q

Effects of 1c on ECG?

A

Increase PR
Increase QRS
Increase QT

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25
Uses of 1c?
Supraventricular arrhythmias (fibrillation and flutter) Premature ventricular contractions Wolff-Parkinson-White syndrome
26
Side effects of 1c?
Pro-arrhythmic - sudden death especially in chronic use Increased ventricular response to supraventricular arrhythmias CNS and GI effects
27
Name some class 1c drugs
Flecainide | Propafenone
28
Effect of beta blockers on the heart?
Diminish phase 4 depolarisation (catecholamine depenedent), therefore - depresses automaticity - prolongs AV conduction - decreases heart rate and contractility Slows AV node conduction velocity
29
Effects on ECG of beta blockers?
``` Increased PR (slowed AV node conduction) Decreased heart rate ```
30
Uses of beta blockers as anti-arrhythmics?
Treat sinus and catecholamine-dependent tachycardia and arrhythmias caused by increased sympathetic activity (eg after MI) Protect ventricles from AF and flutter by slowing AV conduction Convert re-entrant arrhythmias in AV which can cause tachycardias
31
ADRs of beta blockers?
Bronchospasm | Hypotension
32
Contra-indications of beta blockers?
Partial AV block Ventricular failure Asthma
33
Overall effect of potassium channel blockers?
Prolong the action potential duration without altering phase 0, just lengthen the plateau (phase 3) as there is less efflux of potassium
34
Name some potassium channel blockers
Amiodarone | Sotalol
35
Administration of amiodarone?
Orally or IV | Loading dose required due to the long half-life of three months
36
Cardiac effects of amiodarone?
Increase the refractory period and action potential duration Increase the threshold Decrease phase 4 Increase speed of AV node conduction
37
Effects on the ECG of potassium channel blockers?
Increased PR Increased QRS increased QT interval Decreased heart rate
38
Uses of potassium channel blockers?
Wide spectrum - most arrhythmias | Especially AF
39
ADRs of amiodarone?
``` Pulmonary fibrosis Hepatic injury (reversible) Increased LDL cholesterol Thyroid disease Photosensitivity ```
40
Cardiac effects of sotalol?
Increases action potential duration Slows phase 4 (beta blocker) Slows AV conduction
41
Effects on ECG of sotalol?
Increases PR | Decreases heart rate
42
Uses of sotalol?
Supraventricular and ventricular tachycardias
43
ADRs of sotalol?
Pro-arrhythmia - long QT interval - Torsades de Pointes Fatigue Insomnia
44
Uses of amiodarone?
Tachycardia associated with Wolff-Parkinson-White syndrome Many other supraventricular and ventricular tachycardias
45
Examples of calcium channel blockers and how they are administered?
Verapamil - oral or IV Dilitiazem - oral
46
Cardiac effects of calcium channel blockers?
Slows conduction though AV Increased refractory period in AV node Decreased rate of phase 4 spontaneous depolarisation
47
Increased PR Increased or decreased heart rate depending on blood pressure response and baroreceptor reflex
Effect of calcium channel blockers on the ECG?
48
Uses of calcium channel blockers?
Control ventricles in supraventricular tachycardia eg AF Treat re-entrant supraventricular tachycardia around AV node More effective against atrial arrhythmias Hypertension and angina
49
ADRs of calcium channel blockers?
Caution when AV block is present - can get a systole with a beta-blocker Caution in hypotension - can get decreased cardiac output or sick sinus GI
50
Which calcium channel blockers have the greatest effect on heart muscle, vascular smooth muscle and which are in between?
Heart muscle - verapamil Nifedipine - vascular smooth muscle Dilitiazem - intermediate
51
Administration and half-life of adenosine?
Rapid IV bolus | Half-life = seconds
52
Mechanism of action of adenosine?
A nucleoside which binds to A1 receptors and activates adenylyl cyclase Causes efflux of potassium, hyperpolarising the membrane Therefore decreases conduction velocity, prolongs the refractory period and decreases automaticity in the AV node
53
Uses of adenosine?
Terminates (re-entrant) supraventricular tachycardias Hypotension during surgery Diagnosis of CAD
54
Side effects of adenosine?
Flushing Chest pain Hypotension
55
Mechanism of action of digoxin?
Inhibits Na-K-ATPase on cardiac myocytes Causes increased intracellular Na concentration Slows the Na/Ca exchange which pumps calcium out, sodium in More calcium inside the cell, so more is stored in the SR More calcium released in an action potential, causing increased muscle contraction of the heart
56
Overall effects of digoxin?
Increases force of cardiac contraction (positive inotrope) Enhances vagal activity Slows AV conduction and heart rate
57
Uses of digoxin/cardiac glycosides?
Atrial fibrillation and flutter
58
Mechanism of action of atropine?
Causes tachycardia by blocking muscarinic receptors, inhibiting effect of parasympathetic nervous system
59
Effects of atropine on the heart?
Blocks vagal activity causing an increase in AV node conduction speed and increases heart rate
60
Uses of atropine?
Vagal bradycardia
61
Uses of magnesium?
Treats tachycardia resulting from long QT
62
Which drugs can be used for supraventricular arrhythmias?
Adenosine Verapamil Cardiac glycosides Beta blockers
63
Which drugs can be used for supraventricular and ventricular arrhythmias?
Amiodarone Beta blockers Flecainide Propafenone
64
Which drugs can be for ventricular arrhythmias?
Lidocaine | Moacizine

Pharmacology (23 decks)

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