According to recent electrophysiological discoveries, atrial fibrilation is triggered by ectopic beats which in most cases originate in the pulmonary veins, in extensions of left atrial myocardium upon these veins, so called myocardial sleeves. This anatomical structure was first descrited in 1836 by a student of medicine in Breslau Ferd.
Raeuschel, under the tutorship of his profesor J.E.Purkyně.