A patient who is admitted with shortness of breath has a tracing with atrial fibrillation at 140 beats/minute of unknown duration. The nurse begins oxygen per nasal cannula and establishes a saline lock. Which should the nurse prepare to implement next?

A. Transvenous pacemaker placement: A pacemaker is indicated for bradyarrhythmias or heart blocks, not for tachyarrhythmias like atrial fibrillation. This patient’s rapid atrial fibrillation does not warrant pacing and requires rate control and anticoagulation instead. B. Heparin infusion: In new-onset atrial fibrillation of unknown duration, anticoagulation is essential to prevent thromboembolism, especially before attempting cardioversion. Heparin is typically initiated to reduce stroke risk while further evaluation is performed. C. Lidocaine IVPB: Lidocaine is an antiarrhythmic used mainly for ventricular arrhythmias such as ventricular tachycardia or fibrillation. It is not effective for atrial fibrillation and is not part of AF management protocols. D. Sedation for cardioversion: Cardioversion may be appropriate, but not until thrombus risk is evaluated and anticoagulation is established. In AF of unknown duration, immediate cardioversion is avoided unless the patient is unstable, to prevent embolic complications.