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Questions and Answers
What is the mechanism of action for class I antiarrhythmics?
What is the mechanism of action for class I antiarrhythmics?
Na+ Blockers - Inhibition of phase 0 depolarization, slows conduction velocity, decreases automaticity.
What is the mechanism of action for class II antiarrhythmics?
What is the mechanism of action for class II antiarrhythmics?
Beta-adrenergic Blockers - Blocks the effect on SA and AV nodes, decreases slope of phase 4 depolarization in nodal tissue.
What is the mechanism of action for class III antiarrhythmics?
What is the mechanism of action for class III antiarrhythmics?
K+ channel blockers - Prolongs repolarization, prolongs action potential, prolongs effective refractory period.
What is the mechanism of action for class IV antiarrhythmics?
What is the mechanism of action for class IV antiarrhythmics?
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List the Class I antiarrhythmics.
List the Class I antiarrhythmics.
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List the Class II antiarrhythmics.
List the Class II antiarrhythmics.
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List the Class III antiarrhythmics.
List the Class III antiarrhythmics.
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List the Class IV antiarrhythmics.
List the Class IV antiarrhythmics.
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Study Notes
Class I Antiarrhythmics
- Mechanism: Sodium (Na+) channel blockers
- Inhibit phase 0 depolarization in myocardial tissue
- Slow conduction velocity, reducing the speed of electrical impulses
- Decrease automaticity, resulting in reduced heart rate
Class II Antiarrhythmics
- Mechanism: Beta-adrenergic blockers
- Block effects on sinoatrial (SA) and atrioventricular (AV) nodes
- Decrease the slope of phase 4 depolarization in nodal tissue, leading to slower heart rates
Class III Antiarrhythmics
- Mechanism: Potassium (K+) channel blockers
- Prolong repolarization during phase 3 of the action potential
- Lengthen the duration of the action potential and effective refractory period, reducing the likelihood of re-entrant rhythms
Class IV Antiarrhythmics
- Mechanism: Calcium (Ca2+) channel blockers
- Decrease the slope of phase 4 depolarization, impacting nodal tissue conduction
- Block effects primarily on the AV node more than the SA node, slowing down conduction between atria and ventricles
Class I Antiarrhythmics List
- Group A: Procainamide, Disopyramide, Quinidine
- Group B: Lidocaine, Mexiletine, Phenytoin
- Group C: Flecainide, Propafenone
Class II Antiarrhythmics List
- Include all beta-blockers such as Esmolol, Acebutolol, Propranolol, and Metoprolol
Class III Antiarrhythmics List
- Key examples: Amiodarone, Dronedarone, Dofetilide, Ibutilide, Sotalol
Class IV Antiarrhythmics List
- Notable medications: Verapamil, Diltiazem
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Test your knowledge of the Vaughan-Williams classification of antiarrhythmic drugs with these flashcards. Each card covers the mechanism of action for different classes of antiarrhythmics, including class I and class II drugs. Perfect for medical students and healthcare professionals looking to reinforce their understanding.
