dizziness

A 62-year-old man presents to the emergency department with a history of palpitations and dizziness that started suddenly 2 hours ago. He has a history of hypertension and is on lisinopril. He denies chest pain, shortness of breath, or syncope. On examination, his blood pressure is 110/70 mmHg, heart rate is 150 bpm (irregular), respiratory rate is 18 breaths per minute, and temperature is 36.7°C. An ECG is performed, showing an irregularly irregular rhythm with no distinct P waves and a narrow QRS complex. Which of the following is the most appropriate initial management step?

A 70-year-old man with a history of hypertension and heart failure is being managed with an ACE inhibitor. He presents to the emergency department complaining of dizziness, especially when standing up. His blood pressure is 90/60 mmHg, and his other vital signs are stable. Which of the following is the most appropriate initial step in managing this patient?