Key Concepts
Overview
Antiarrhythmic drugs are classified by the Vaughan Williams system into four classes based on their primary mechanism of action. Class I agents block Naโบ channels; Class II are beta-blockers; Class III block Kโบ channels (prolong repolarization); Class IV are calcium channel blockers. Amiodarone is the most widely used antiarrhythmic because it has properties of all four classes. NCLEX-RN priorities: understanding the mechanism behind the clinical effect, recognizing the most dangerous side effects (proarrhythmia โ when an antiarrhythmic causes a NEW arrhythmia), monitoring the QT interval for torsades risk, and knowing the amiodarone toxicity profile (pulmonary, thyroid, hepatic, ocular, dermatologic). On the exam, writers often pair stable-sounding options with unstable dataโnotice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that can fail quietly. When two answers feel partly right, pick the one that reduces imminent harm and matches orders for the...