Friendly Advice Goes Awry

ANSWER
The correct interpretation is coarse atrial fibrillation with a rapid ventricular response and left-axis deviation.

Coarse atrial fibrillation is evidenced by the irregularly irregular rhythm with a normal QRS duration and flutter/fibrillation waves arising from the atria. Rapid ventricular response is defined as a ventricular response > 100 beats/min (seen in this case). Finally, an R-wave axis between –30° and –90° is indicative of left-axis deviation.

Correcting the patient’s hypokalemia and hypomagnesemia resulted in a return to normal sinus rhythm. At one-year follow-up, he had had no further episodes of atrial fibrillation.