arrhythmia drugs Flashcards
arrhythmia definition
abnormal rhythm in the heart can be atrial or ventricular in nature - atrial fibrillation - atrial flutter - Ventricular fibrillation - ventricular tachycardia
Why does arrhythmia occur
usually due to an existing heart issue
- myocardial infarction causing issues in conduction, unidirectional conduction can start ectopic beats
- rentering tachycardia
- atrial fibrillation due to hyperthyroidism
Drugs for arrhythmia classes
1a: intermediate acting, procainamide
1b: fast acting, lidocaine
1c: slow acting, flecainide
2: beta blockers, metoprolol, propanolol
3: potassium blockers, amiodarone
4: calcium channel blockers, (nonDHP) verapamil, diltazem
What is the MOA of type 1
Procainamide Blocks sodium channels Slow down phase 0 depol procainamide slows down repolarisation as well increase ERP, APD decrease conductivity and automaticity
Lidocaine decreases ERP and APD
shortens repol
slows down automaticity but not conductivity
Flecainide
shortens repol
slows down both automaticity and conductivity
Indications and adverse effect of type 1?
Flecainide:
- used as a last resort in response to refractory tachycardia that might lead to fibrillation bc of cardiosuppresant effects
What is the MOA of type 2
betablockers:
1. reduced calcium induced calcium released decreasing contractility
hence slows the phase 4 depolarisation
SA node and AV node block
decreases automaticity
Indications and adverse effects of beta blockers
Indications 1. hypertension 2. angina/heart failure 3. atrial fibrillation 4. rentrant tachycardia reduces death post MI
WHat is the MOA of type 3
potassium channel blockers amiodarone
blocks K+ leak channels: slows down phase 3 repolarisation
increases erp and apd
acts on sodium channels, adrenergic channels, calcium channels
Indications and adverse effects of type 3
PK: 50% excreted in first few days, next 50 % will be excreted over weeks/months!
Indication: maintaining normal sinus rhythm, rentrant tachycardia
Adverse effects: heart block, bradycardia
MOA of type 4
calcium channel blockers - verapamil, diltazem
3 pathways:
-SAN and AVN block, cardiosuppressive effects for ventricular and atrial fibrillation,
- blood vessel relaxation
- cardiac muscle relaxation
phase 4 depol prolonged, increased ERP and APD
INdication and adverse effects of CCB
indicatioN: 1. angina, hypertension 2. rentrant supraventricular tachy, atrial fib adverse effects: - cardiosuppressive, hypotension
What is used in emergency supraventricular tachycardia
adenosine!
- causes AV node refractory period increased, activation of K+ leak channels, calcium channel inhibition
adverse effects: flushing SOb hypotension AV block
