Anti arrhythmic Flashcards
Describe the action potential graph and phases
Phase 0: Upstroke
- Depolarization as Na+ channels open
Phase 1: Early fast repolarization
- K+ starts going out
Phase 2: Plateau
- Na+ going in «_space;K+ going out
Phase 3: Repolaristion
- Na+ channel closes and K+ still going out
Phase 4: Diastole. No movement in Na+ and K+
What is the effective refractory period?
Period of time where a new action potential cannot be initiated
What does the P wave represent?
Atrial contraction
- Wave of depolarization that spreads from SA node throughout atria
What does the PR wave represent?
Time between the onset of atrial depolarization and the onset of ventricular depolarization.
Time taken for impulse to travel from atrium to ventricles.
Prolonged PR wave suggestive of AV block as the impulse is held at the AV node for a longer period of time.
What does the QRS complex represent?
Ventricular depolarization.
R - left heart
S- right heart
What does the QT interval represent?
Duration of action potential (ie. ventricular depolarization and repolarization)
What does ST represent?
Ventricular repolarization
Describe what is excitability
Cell can change its internal electrical balance to reach threshold
Describe automaticity
Cell can generate an electrical impulse without being stimulated
Describe conductivity
Cell can transfer an electrical impulse to the next cell
List ALL the classes of antiarrhythmic drugs
- Na+ channel inhibitors: Class 1A,B,C
- Beta blockers
- K+ channel inhibitors
- Ca2+ channel inhibitors
Name a Class 1A anti arrhythmic drug and its MOA
Procainamide
- Slows atrial depolarization
- Reduces conductivity and automaticity
Name a Class 1B anti arrhythmic drug and its MOA
Lidocaine
- Slows atrial depolarization
- Shortens ventricular repolarization
- Reduces automaticity
Name a Class 1C anti arrhythmic drug and its MOA
Flecainide
- Slows atrial depolarization
- Shortens ventricular repolarization
Procainamide is a Class 1_ antiarrhythmic drug that _ ERP and action potential duration.
Procainamide is a Class 1A antiarrhythmic drug that increases ERP and action potential duration.
Lidocaine is a Class 1_ antiarrhythmic drug that _ ERP and _ action potential duration.
Lidocaine is a Class 1B antiarrhythmic drug that does not change ERP and decreases action potential duration.
Flecainide is a Class 1_ antiarrhythmic drug that _ ERP and action potential duration.
Flecainide is a Class 1C antiarrhythmic drug that has little to no effect on ERP and action potential duration.
What is the clinical use of Flecainide?
Refractory ventricular tachycardias that tend to progress to VF
List 2 beta blockers
Metoprolol succinate
Bisoprolol
Describe the MOA of beta blockers
- Reduce phase 4 depolarization
- No change in ERP & APD
- Prolonged AV conduction
- Reduces HR and contractility (sympathetic NS)
Block beta 1 adrenergic receptors in the heart
-> reduce effects of NE and epinephrine
-> reduced HR and contractility
What is the clinical indication for beta blockers?
Any condition that is primarily caused by over-activation of sympathetic nervous system.
- Tachycardia caused by sympathetic activation
- Atrial fibrillation
Name a potassium channel blocker and its MOA/effect on the heart
Amiodarone
- Prolongs phase 3 repolarization
- Increases ERP & APD
State the unique PK characteristic of amiodarone
Amiodarone is a potassium channel blocker.
It undergoes hepatic metabolism to a BIOACTIVE METABOLITE.
This means that after discontinuation, effects are maintained for 1-3 months.
List the potassium channel blocker and its clinical indications
Amiodarone
- Used to MAINTAIN normal sinus rhythm in pts with AF
- Prevention of reentrant ventricular tachycardia
