Pharm Session 3.1 Cardaic Arrthmias

Question 1

Describe the effect on AP of class I drugs

Answer 1

• Na+ channel blockers

- Upstroke is offset to the right and there is slowing of conduction but minimal effect on AP duration

Question 2

Describe the effect on AP of Class II drugs

Answer 2

• Beta blockers
• Increase AP duration, slows down depolarisation (0)
• Decreases automaticity (cell’s ability to spontaneously generate APs and depolarise)

Question 3

Describe the effect of Class III drugs on AP

Answer 3

• K+ channel blockers
• Increase AP duration and increase refractory period
• Depolarisation speed is normal

Question 4

Describe the action of class IV drugs on AP

Answer 4

• Ca2+ channel blockers
• decreases spontaneous depolarisations
• slows down phase 4
• slower upstroke

Question 5

Describe the effect of class IV drugs on the SA node AP

Answer 5

• increases the refractory period

- slows sown upstroke

Question 6

Describe the effect of class II drugs on cardiac (SA node) AP

Answer 6

• Beta blockers

- Decrease funny current slope (fight sympathetic drive) and reduce automaticity

Question 7

Describe Wolf Parkinson White Syndrome

Answer 7

• Accessory pathway connecting ventricles to atria called Bundle of Kent
• The AP drivers down AV –> Purkinje fibres and then gets passed back into the atria via the Bundle of Kent.
• Results in tachycardia and palpitations

Question 8

What are the two main targets when treating arrhythmias?

Answer 8

• targeting abnormal impulse generation

- targeting abnormal conduction through tissue

Question 9

Give an example of a class IA drug an its effect on the AP

Answer 9

• Na+ blocker - Procainamide
• Decreases conduction (slower phase 0 of AP)
• Increases refractory period
• Decreases automaticity by slowing down phase 4

Question 10

Give an example of a Class IB drug and its use + 1 contra-indication

Answer 10

• Na+ channel blocker - lidocaine
• Use: pts with ischaemia and ventricular tachycardia (good for decreasing slow of phase 0)
• Not used for Atrial arrhythmias or AV junctional arrythmias

Question 11

Give an example of a type IC drug and its use + 1 contra-indication

Answer 11

• Fleconide
• Used: supraventricular Arrhythmias (fibrillation and flutter) + WPW + premature ventricular contraction
• Contraindication: it increases ventricular response to supraventricular arrhythmias, therefore should not be given in A-flutter because heart will begin to beat at the rate of the flutter and lead to VT

Question 12

Give 2 examples of Class II drugs and their effect on AP

Answer 12

• Bisoprolol and Propranolol
• increase AP duration and refractory period at AV node (slow AV node conduction velocity)
• Decrease phase 4 depolarisation (blocks effects of adrenaline)

Question 13

Give the uses and side effects of beta blockers

Answer 13

• Uses: treats sinus and catecholamine dependent tachy by slowing AV conduction
• Side effects: bronchospasm and hypotension –> Don’t use in in AV node partial block or HF

Question 14

Give an example of a class III drug and effect on AP

Answer 14

• Amiodorone
• Increases refractory period and AP duration
• Decreases speed of AV node conduction

Question 15

What are the uses and side effects of Amiodorone?

Answer 15

• Use: wide spectrum, good for most arrhythmias
• Side effects: very fat soluble drive, can get deposited anywhere in body and cause problems (pulmonary fibrosis, thyroid issues, hepatic injury)

Question 16

Give an example of a class IV drug and its effect on AP

Answer 16

• Verapamil

- Acts on plateau stage and sloes conduction at AV node + increases AP duration + increases refractory period at AV

Question 17

What are the uses and side effects of verapamil?

Answer 17

• Uses: controls ventricles during supraventricular tachy and blocks AV node to stop re-entry
• Side effects: caution if AV block/hypotension present because can lead to asystole if combine with a Beta blocker
• **Bisoprolol and verapamil shouldn’t be used together without a pacemaker

Question 18

Give an example and uses of a cardiac glycoside

Answer 18

• Digoxin
• enhances vagal activity (increases K+ currents, decreases Ca2+ currents and increases refractory period) + slows down AV conduction and heart rate
• It is an adjunct, not used alone. Can be added to verapamil or Bisoprolol if in persistent AF

Question 19

What is atropine?

Answer 19

• Selective muscarinic antagonist
• Works by blocking vagal activity to speed AV conduction and heart rate
• Used to treat vagal bradycardia

Question 20

What drugs do you use in AF? What are the two targets?

Answer 20

• Want to slow down conduction through AV node because it reduces ventricular response
• Rate control: bisoprolol, verapamil, dilitiazem (+- digoxin)
• Rhythm control: sotalol, flecainide with bisoprolol, Amiodorone

Question 21

What drugs can you give for VT?

Answer 21

• Metoprolol
• Lignocaine
• Amiodorone

Question 22

Should flecainide be used alone in AF?

Answer 22

• No because induces VT if used alone

- Instead give AV nodal blocking drugs to reduce ventricular rates in flutter

Question 23

What is the best TRX for WPW? What is a contra-indications?

Answer 23

• Flecainide
• Amiodorone
• Not good for long term TRX, pts will have an ablation long term

Question 24

List drugs that could be used in re-entrant SVT? What pathway are we aiming to target?

Answer 24

• Re-entrant SVT uses AV node specifically
• Acute TRX: adenosine, verapamil, flecainide because they block AV node
• Chronic repeated issues: Bisoprolol, verapamil, flecainide, Amiodorone (last choice b/c of numerous side effects)

Question 25

What drugs are used for ectopic beats? What is the target we are aiming for?

Answer 25

• Used drugs that reduce automaticity

- Bisoprolol, flecainide or Amiodorone

Question 26

Why drugs are used to treat sinus tachy?

Answer 26

• Bisoprolol and verapamil

- Ivabradine: affects conduction through SA node and doesn’t drop BP like verapamil and bisoprolol