A 28-year-old male presents to the Emergency Department with sudden onset of palpitations for the past 45 minutes. He admits to using cocaine at a party approximately 2 hours prior to symptom onset. He denies any previous cardiac history but acknowledges recreational cocaine use on weekends.

Observations:

Heart rate: 190 beats per minute, regular

Respiratory rate: 22 breaths per minute

Blood pressure: 158/92 mmHg

Temperature: 37.9°C

Oxygen saturation: 97% on room air

GCS: 15/15

Agitated and combative

An ECG is taken:

He has received 6mg of adenosine followed by 12mg of adenosine, both without successful cardioversion.

What is the most appropriate next step in management?