What is your diagnosis? (ANSWERED)

A 36-year-old male with no significant medical history presented
to the ED complaining of 30 minutes of palpitations,
described as a rapid, irregular heart beat. The patient reported
mild shortness of breath and fatigue but denied chest pain,
nausea or sweating. He described several similar episodes
in the past, which had always resolved spontaneously within
two hours. Earlier that day, the patient had exercised strenuously
and did not drink much water afterward. He denied
tobacco, intravenous drugs, cocaine or methamphetamine use,
and drank alcohol only occasionally.

The patient was placed on the cardiac monitor and a 12-lead
ECG was obtained

Atrial Fibrilation with LBBB and rapid ventricular response.