Pharm Session 3.1 Cardaic Arrthmias Flashcards
Describe the effect on AP of class I drugs
- Na+ channel blockers
- Upstroke is offset to the right and there is slowing of conduction but minimal effect on AP duration
Describe the effect on AP of Class II drugs
- Beta blockers
- Increase AP duration, slows down depolarisation (0)
- Decreases automaticity (cell’s ability to spontaneously generate APs and depolarise)
Describe the effect of Class III drugs on AP
- K+ channel blockers
- Increase AP duration and increase refractory period
- Depolarisation speed is normal
Describe the action of class IV drugs on AP
- Ca2+ channel blockers
- decreases spontaneous depolarisations
- slows down phase 4
- slower upstroke
Describe the effect of class IV drugs on the SA node AP
- increases the refractory period
- slows sown upstroke
Describe the effect of class II drugs on cardiac (SA node) AP
- Beta blockers
- Decrease funny current slope (fight sympathetic drive) and reduce automaticity
Describe Wolf Parkinson White Syndrome
- 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
What are the two main targets when treating arrhythmias?
- targeting abnormal impulse generation
- targeting abnormal conduction through tissue
Give an example of a class IA drug an its effect on the AP
- Na+ blocker - Procainamide
- Decreases conduction (slower phase 0 of AP)
- Increases refractory period
- Decreases automaticity by slowing down phase 4
Give an example of a Class IB drug and its use + 1 contra-indication
- 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
Give an example of a type IC drug and its use + 1 contra-indication
- 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
Give 2 examples of Class II drugs and their effect on AP
- 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)
Give the uses and side effects of beta blockers
- 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
Give an example of a class III drug and effect on AP
- Amiodorone
- Increases refractory period and AP duration
- Decreases speed of AV node conduction
What are the uses and side effects of Amiodorone?
- 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)
Give an example of a class IV drug and its effect on AP
- Verapamil
- Acts on plateau stage and sloes conduction at AV node + increases AP duration + increases refractory period at AV
What are the uses and side effects of verapamil?
- 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
Give an example and uses of a cardiac glycoside
- 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
What is atropine?
- Selective muscarinic antagonist
- Works by blocking vagal activity to speed AV conduction and heart rate
- Used to treat vagal bradycardia
What drugs do you use in AF? What are the two targets?
- 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
What drugs can you give for VT?
- Metoprolol
- Lignocaine
- Amiodorone
Should flecainide be used alone in AF?
- No because induces VT if used alone
- Instead give AV nodal blocking drugs to reduce ventricular rates in flutter
What is the best TRX for WPW? What is a contra-indications?
- Flecainide
- Amiodorone
- Not good for long term TRX, pts will have an ablation long term
List drugs that could be used in re-entrant SVT? What pathway are we aiming to target?
- 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)
