Antiarrhythmics — Mechanisms and Classification

Which of the following antiarrhythmic drugs blocks both sodium and potassium channels and is classified as a Class IA agent?

A Class III antiarrhythmic agent prolongs the action potential duration and QT interval primarily by which mechanism?

A 52-year-old man with a history of myocardial infarction 6 months ago presents with recurrent episodes of sustained ventricular tachycardia. Electrophysiology studies confirm re-entrant mechanism. Which antiarrhythmic drug is the drug of choice for long-term suppression of this arrhythmia?

A 58-year-old man with a history of myocardial infarction presents with recurrent ventricular tachycardia. Regarding antiarrhythmic drug selection and properties, all of the following statements are correct EXCEPT:

A 52-year-old man with a history of hypertension and left ventricular hypertrophy presents to the emergency department with palpitations and dyspnea. His ECG shows a regular narrow-complex tachycardia at 180 bpm. Carotid sinus massage fails to terminate the arrhythmia. Intravenous adenosine 6 mg is administered but produces only transient slowing of the heart rate without termination. What is the most appropriate next step in management?