MSRA-0050

MSRA-0050

A 49-year-old man comes to the emergency department complaining of dizziness and shortness of breath on exertion for the past 3 days. He reports experiencing palpitations during this time but denies any chest pain or cough. The patient has a history of hypertension and angina, for which he takes amlodipine and GTN spray, respectively. Upon examination, he appears alert and oriented, but his vital signs reveal a heart rate of 170 BPM, respiratory rate of 25 breaths/min, and blood pressure of 72/50 mmHg. An ECG shows a narrow complex irregular tachycardia without P waves. What is the most crucial next step in management?