Cardiac Drugs Flashcards
What are the examples of Class 1A drugs and how are they administered?
- Procainamide
- Quinidine
- Disopyramide
Both Oral or IV
What are examples of Class 1B drugs and how are they administered?
- Lidocaine (IV)
- Mexelitine (Oral)
What are the examples of Class 1C drugs and how are they administered?
- Flecainide
- Propafenone
Both Oral or IV
What is the mechanism of action of Class 1 cardiac drugs?
-Na+ channel blocker
What are the effects on the cardiac activity for Class 1A cardiac drugs?
- Decrease in conduction
- Increase in refractory period
- Decrease in automaticity by decreasing slope of phase 4 and fast potentials
- Increase in threshold
What are the effects on the cardiac activity for Class 2 cardiac drugs?
- Increase in action potential duration in AV node to slow AV conduction velocity
- Decrease phase 4 depolarization (catecholamine dependant)
What are the effects on the cardiac activity for Class 1B cardiac drugs?
- Fast binding offset kinetics
- APD slightly decreased (normal tissue)
- Increase in threshold potential
- Decrease in phase 0 conduction in fast beating or ischaemic tissue
- No change in phase 0 in normal tissue (no tonic block)
What are the effects on the cardiac activity for Class 1C cardiac drugs?
- Very slow binding offset kinetics
- Substantially decrease phase 0 in normal hearts
- Decrease automaticity by increasing threshold
- Increase in action potential duration (APD) and increase in refractory period especially in rapidly depolarizing atrial tissue
What are examples of Class 2 cardiac Drugs and their route of administration?
- Propranolol (oral, IV)
- Bisoprolol (oral)
- Metoprolol (oral)
- Esmolol (IV)
What is the mechanism of action of Class 2 cardiac drugs?
Anti-adrenergic
What is the effect on an ECG of Class 2 cardiac drugs?
- Increase in PR
- Decrease in HR
What are the uses of Class 2 cardiac drugs?
- Treatment of sinus and catelocholamine dependant tachycardia
- Converting re-entrant arrhythmias at AV node
- Protecting the ventricles from high atrial rate to slow AV conduction
What are the side effects of Class 2 cardiac drugs?
- Bronchospasm so be careful with asthmatic
- Hypotension
When can’t Class 2 cardiac drugs be used?
- Partial AV block
- Ventricular failure
What are the effect of Class 1A cardiac drugs on the ECG?
- Increased QRS
- Increased QT
+/- PR
What are the uses of Quinidine?
- Quinidine has anti-cholinergic to speed AV conduction
- Used with digitalis, beta blocker and Ca2+ channel blocker.
- Quinidine maintains sinus rhythms in atrial fibrillation and flutter, to prevent recurrence, Brugada syndrome.
What are the uses of IV Procainamide?
-IV Procainamide used acutely to treat supraventricular and ventricular arrhythmias.
What are some side effects of Class 1A cardiac drugs?
- Hypotension
- Pro-arrhythmia (generation of a new arrhythmia e.g. Torsade de Points)
- Reduced cardiac output
- Dizziness, Confusion, Insomnia, Seizure at high dose
- Gastrointestinal effects common
- Lupus-like syndrome (esp procainamide)
What is the effect of Class 1B drugs on the ECG?
- None in normal
- In fast beating or ischaemic, Increase in QRS
What are the uses of Class 1B cardiac drugs?
- Acute: Ventricular tachycardia especially during ischaemia
- Not used in atrial arrhythmias or AV junctional arrhythmias
What are the side effects of Class 1B cardiac drugs?
- Less pro-arrhythmic than Class 1A
- CNS effects such as dizziness and drowsiness
- Abdominal upset
What are the effects of Class 1C cardiac drugs on the ECG?
- Increase in PR
- Increase in QRS
- Increase in QT
What are the uses of Class 1C cardiac drugs?
- Wide spectrum
- Used for supraventricular arrhythmias (fibrillation and flutter) + Class 2
- Premature ventricular contractions
- Wolff-Parkinson White syndrome
What drug use should be avoided in supra-ventricular arrhythmias?
- Class 1C drugs such as Flecainide
- Can slow the atrial rate enough for the ventricles to respond
- This can lead to abnormally fast rhythm of the ventricles due to increased ventricular response to supraventricular arrythmias
- Use of Class 2 or Class 3 drugs as well
