Euphoric Man, Offbeat Rhythm

ANSWER

This ECG shows atrial fibrillation with aberrancy and a rapid ventricular response, left-axis deviation, and a left bundle branch block (LBBB).

While the physical exam can identify atrial fibrillation with a rapid ventricular response, an ECG is necessary to determine left-axis deviation and LBBB.

Left-axis deviation is evidenced by an R axis of –36°.

Aberrancy is identified by a QRS duration > 120 ms with poor R wave progression in precordial leads V₁ to V₃ and a wide positive R wave in V₅ and V₆.

Of note, the 10th beat on the rhythm strip is narrow and complex and is not aberrantly conducted.