An Unexpected Narrow QRS Complex -1-

Author(s)	A.A.M. Wilde
NHJ edition:	2009:08,307
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

A 95-year-old woman presents with palpitations. She has no relevant medical history and the present complaint is several days old. She is not using any medication. Physical examination reveals an irregular pulse and heart beat (pulse deficit 20 beats/min) and no further abnormalities. Her ECG is shown in figure 1 (only the precordial leads are shown).

How would you judge this ECG?

Answer