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Anti-arrhythmics > Drugs > Flashcards

Drugs Flashcards

1
Q

What is the Vaughan Williams classification?

A

1- Na channel blockers

2 - Beta blockers

3 - K channel blockers

4 - Ca channel blockers

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2
Q

How do class 1 drugs work?

A

Stabilising the cell membrane via decreased excitogenicity

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3
Q

What do type 1a drugs do? Name an example

A

Slow conduction velocity in both atrial and ventricular cells. Higher doses slows AV conduction. Block K leading to slower repolarisation.
Procainamide

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4
Q

When are type 1a drugs used?

A

Ventricular and atrial arrhythmias especially post MI

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5
Q

What do type 1b drugs do? Example.

A

Reduces AP duration in abnormal ventricular cells. Slows recovery of sodium channels.
Does not shorten effective refractory period

Lignocaine

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6
Q

When are type 1b drugs used?

A

Ventricular arrhythmias post MI or dig toxicity

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7
Q

What do type 1c drugs do? Example

A

Depressants of sodium current. Markedly slows conduction velocity in atria and ventricles.
Increased QRS duration.

Flecainide
Used for refractory arrhythmias

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8
Q

How do beta blockers work?

A

Block cardiac beta receptor response to sympathetic nervous system stimulation.
Decreased G-protein S responses and decreased cAMP.

Also interfere with the binding of epinephrine and other stress hormones ro receptors

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9
Q

B1 receptors are located in?

A

The heart and kidneys

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10
Q

B2 receptors are located in?

A

Lungs, GI, liver, uterus, smooth muscle, skeletal muscle

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11
Q

How do B blockers affect action potential

A

Decreased rate of phase 4 depolarisation + slows SA node rate.

Prolonged PR on ecg

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12
Q

How do potassium channel blockers affect the AP?

What is an example?

A

Prolongs by blockade of K - aka lengthed repolarisation

Amiodarone

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13
Q

Potassium blockers do what to the refratory period?

A

Increase in the effective refractory period

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14
Q

What can potassium channel blockers cause?

A

Torsades, by QT prologation

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15
Q

Amiodarone affects atrial or ventricular tissues?

A

Both, including AV node and SA node

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16
Q

Half life of amiodarone?

A

29 days

17
Q

Which receptors does amiodarone work on?

A

Beta

Potassium

Sodium

Calcium

18
Q

What are the effects of amiodarone?

A

Slow AV and SA node conduction

Increased refractory period

Slowed intracardiac AP conduction

19
Q

Side effects of amiodarone?

A

Interstitial lung disease

Hyper/hypothyroid

Corneal microdeposits

Jaundice/hepatitis

Blue grey skin discolouration

Peripheral neuropathy

Epididymitis

Gynaecomastia

20
Q

When is amiodarone contraindicated?

A

Pregnancy + breast feeing

Sinus node bradycardia

AV block

2/3rd degree HB

21
Q

How does digoxin work?

A

Inhibits Na/K ATPase of cell membrane

This increases intracellular sodium levels, reverses sodium-calcium exchanger, increases intracellular calcium and therefore increases myocardial contraction

22
Q

How is the baro-receptor effected by digoxin?

A

Improves baroreceptor sensitivity by inhibition of sodium pump

23
Q

Cardiac effects of digoxin?

A

Increased ventricular ejection, decreased ED size, higher CO, increased renal perfusion

24
Q

How does it affect sthe autonomic nervous system?

A

Decreases symp. Increases parasymp via vagus (AV node delay)

25
Q

How does digoxin affect the refractory period?

A

Increases in the SA and AV nodes. Decreased in atria and ventricles

26
Q

Side effects of digoxin?

A

Anorexia, N/V, diarrhoea, blurred vision, confusion, drowsiness, dizziness, insomnia, agitation, depression.

Rare - psychosis, delirium, amnesia, convulsions

Shortened QRS, A or V extrasystoles, VF/VT, heart block, paroxysmal atrial tachycardia with AV block

27
Q

How does digoxin affect the ecg?

A

Increased PR, decreased QT, flattened T waves.

Can cause AV junctional rhythm and ectopics

28
Q

How does adenosine work?

A

Affects A1 adenosine receptors in SA and AV. Inhibits adenylyl cyclase, reducing cAMP -> cell hyperpolarisation

29
Q

How does high dose adenosine work?

A

Hyperpolarisation through outward potassium flux and reduced calcium current leading to a temporary block in conduction

Also causes vascular dilation

30
Q

Side effects of adenosine

A

Facial flushing, chest rash, light headedness, diaphoresis, nausea, metallic taste

31
Q

When is adenosine contraindicated?

A

2nd/3rd degree HB

sick sinus syndrome

Long QT

severe hypotension

Decompensated HF

Asthma

Drug induced tachycardia

32
Q

What % of body magnesium is in heart and smooth muscle

A

35%

33
Q

What are the effect of Mg

A

Inhibits acetylcholine and noradrenaline release. Antagonises NDMA

34
Q

How does Mg affect the cell membrane?

A

Stabilises it via acting as a cofactor for Na/K ATPase.

Is bound to cellular ATP

35
Q

What are the effects of Mg on cardiac tissue?

A

Prolongs sinus node recovery, reduced automaticity and AV node/His conduction

36
Q

What does low Mg cause in patients with myocardial ischaemia?

A

Facilitates Ca2 influx, which causes cellular death

Anti-arrhythmics (2 decks)

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