Wide Complexes Intervening Regular Sinus Rhythm - 4

Author(s)	A.A.M. Wilde
NHJ edition:	2008:05,175
These Rhythm Puzzles have been published in the Netherlands Heart Journal and are reproduced here under the prevailing creative commons license with permission from the publisher, Bohn Stafleu Van Loghum.
The ECG can be enlarged twice by clicking on the image and it's first enlargement

Figure 1

A 55-year-old male without cardiac history is complaining of an irregular heartbeat. Physical examination and an echo reveal no abnormalities. His ECG (extremity leads only) is shown in figure 1.

What is your diagnosis?

Answer