Slow and steady doesn’t always win the race

What is your first priority?

A short while later.

The patient is attached to the cardiac monitor which shows a regular rhythm with a rate between 28-36

IV access is obtained, and blood samples are sent for full blood count, electrolytes, troponin and c-reactive protein.

The patient appears fatigued but can talk to you and explain his symptoms. He is visibly breathless but is completing his sentences.  On examination, his GCS 15 out of 15. BP 104/54, sats 97% room air, RR 20. Chest clear, normal heart sounds, no clinical signs of fluid overload and abdomen soft non-tender. You ask for a 12-lead electrocardiogram (ECG) which looks like this:

Fig.1 via Life in the Fast Lane (Click the image to emlarge it)

What is the next step in management?

You prescribe doses of atropine 500mcg up to a maximum of 3mg which does nothing.

The patient starts to become more lightheaded and increasingly fatigued and although he is rousable he is no longer as talkative as before. His HR remains between 26-36, RR is now 32 with a BP of 92/56 and his oxygen saturations are 94% on room air which improves to 98% with 2L O2 via nasal canula.

What is the most appropriate next step?