Vaughan Williams Class 3 (electrolyte function) does what?

Vaughan Williams Class 3 (electrolyte function) does what?

• A. Inhibits calcium channels
• B. Slows sodium channels
• C. Prolongs repolarization
• D. Blocks potassium channel

Answer: (D)

Class 3 antiarrhythmics act by blocking potassium channels in cardiac cells. This blockade reduces outward potassium current during the final phase of the action potential, slowing repolarization. The result is a longer action potential duration and a longer refractory period, which helps prevent re-entrant tachyarrhythmias and can terminate certain arrhythmias. Prolonging repolarization is a consequence of the potassium channel blockade, but the defining action of this class is the direct inhibition of potassium channels. This sets them apart from drugs that primarily inhibit calcium channels (Class IV) or slow sodium channels (Class I).

Class 3 antiarrhythmics act by blocking potassium channels in cardiac cells. This blockade reduces outward potassium current during the final phase of the action potential, slowing repolarization. The result is a longer action potential duration and a longer refractory period, which helps prevent re-entrant tachyarrhythmias and can terminate certain arrhythmias. Prolonging repolarization is a consequence of the potassium channel blockade, but the defining action of this class is the direct inhibition of potassium channels. This sets them apart from drugs that primarily inhibit calcium channels (Class IV) or slow sodium channels (Class I).