Cardiovascular Drugs USMLE Step 1 Practice Question

A 55-year-old man with a history of myocardial infarction two years ago presents to the emergency department complaining of palpitations and mild shortness of breath that began approximately three hours ago. His blood pressure is 118/76 mmHg, heart rate is 132 beats per minute and irregularly irregular, respiratory rate is 18 breaths per minute, and oxygen saturation is 96% on room air. An electrocardiogram confirms atrial fibrillation with rapid ventricular response. Echocardiography performed during his prior hospitalization documented an ejection fraction of 35% with an anterior wall motion abnormality. A resident considers initiating flecainide for rhythm control, but the attending physician advises against it due to the significantly increased risk of life-threatening ventricular arrhythmias in patients with structural heart disease. Flecainide belongs to which of the following antiarrhythmic classes?