Ashman phenomenon

The Ashman phenomenon, also known as Ashman beats, describes a particular type of wide complex tachycardia (fast rhythm of the heart) that is often seen in atrial fibrillation. In particular, it is important because it can be misinterpreted as non-sustained ventricular tachycardia.

Ashman beats are described as wide complex QRS complexes that follow a short R-R interval preceded by a long R-R interval. This wide QRS complex represents an abberantly conducted complex that originates above the AV node, rather than a complex that originates in either the right or left ventricle.

Reference

 * 1) Ashman R, Byer E. Aberration in the conduction of premature ventricular impulses. J La State Med Soc 8:62, 1946