Arrhythmias - Therapy Flashcards
Describe the basis of the Vaughan-Williams classification of anti-arrhythmic drugs
IA - (Moderate) sodium channel blockade e.g. quinidine
IB - (Weak) sodium channel blockade e.g. lidocaine
IC - (Strong) sodium channel blockade e.g. flecainide
II - beta-adrenoreceptor antagonist e.g. atenolol
III - Prolong refractoriness (slow K moving out cells) e.g. amiodarone
IV - CCB e.g. verapamil
V - Others i.e. digoxin
Describe class I anti-arrhythmic drugs
- Membrane stabilising: decrease amplitude, velocity of conduction
Describe class III anti-arrhythmic drugs
- Increase action potential duration
- Prolongs repolarisation
Describe class III anti-arrhythmic drugs
- Increase action potential duration
- Prolongs repolarisation
Describe class IV anti-arrhythmic drugs
- CCB (L-type)
- Depress depolarisation in both nodes
- Shorten plateau
- Show use dependence
Describe digoxin
- Inhibits Na/KATPase pump
- Increases vagal tone
- Reduces refractory period
- Short half-life, increased in renal impairment
- Commonly used in elderly
- Nausea, vomiting, Brady/tachycardia, arrhythmias, xanthopsia
Describe digoxin
- Cardiac glycoside: increase HR
- Inhibits Na/KATPase pump
- Increases vagal tone
- Reduces refractory period
- Increases Ca, inotropic effect
- Short half-life, increased in renal impairment
- Commonly used in elderly
- Nausea, vomiting, Brady/tachycardia, arrhythmias, xanthopsia
- Give digibind if toxic, toxicity worse if K levels low
Describe the indications for anti-coagulant therapy
- AF: risk of stroke, peripheral emboli
- Metallic heart valves
- Prophylactic: pre-surgery, bed rest
Describe the ideal anti-coagulant
- Oral
- No need for monitoring
- No interactions
- 1/2 a day for everyone
Describe the ideal anti-coagulant
- Oral
- No need for monitoring
- No interactions
- 1/2 a day for everyone
Describe warfarin
- Anti-coagulant
- Vitamin K antagonist
- Monitor
- INR = 2.5-4 (normal = 1)
- Bleeding, drug interactions, teratogenic
