Etienne Jules Marey published the first tracing of irregular arterial pulse consistent with atrial fibrillation in his book, "Physiologie medicale de la circulation du sang," in 1863.
James Mackenzie also recorded tracings of irregular arterial pulse with the polygraph and called them " auricular paralysis ". In his observations, a significant number of patients presented with rheumatic mitral stenosis. These early observations are discussed in the section Sphygmography.
Although techniques of graphic recording of arterial pulse were used with increasing frequency during the second half of the 19th century, atrial fibrillation was not recognized as a distinct electropathological entity until the first decade of the 20th century and the introduction of electrocardiogram.
As mentioned earlier, Einthoven reported the first electrocardiogram of atrial fibrillation in his article "Le telecardiogramme" which was published in 1906. Einthoven did not know the mechanism and clinical significance of this arrhythmia.
In 1909, Carl Julius Rothberger and Heinrich Winterberg from Germany showed the tracing of atrial fibrillation in human and called it "Arhythmia perpetua".
They also defined its characteristics as follows: The absence of P waves, irregular ventricular rate, and the presence of oscillation representing fibrillary waves. A few months later, Thomas Lewis reported his electrocardiographic observations of irregular rhythms attributing them to a condition that he called auricular fibrillation (atrial fibrillation). He also emphasized in his article that this rhythm disorder was a "common clinical condition".