Mechanisms of Atrial Flutter : From MacWilliam in 1887 to Miyauchi in 2005

John Alexander MacWilliam in 1887 was probably the first to describe the abnormal atrial rhythm known as atrial flutter. His work opened the way of correlating clinical electrocardiography with the actual visualization of the abnormal beating in the hearts of experimental animals. In his 1887 article in the Journal of Physiology he described the electrically-induced atria arrhythmias this way: ‘‘The application of the current sets the auricles into a rapid flutter, the rapidity of which largely depends upon the excitability of the auricular tissue and the strength of the current employed. The movements are regular; they seem to consist of a series of contraction originating in the stimulated areas and then spreading over the rest of the tissues. The movement does not show any distinct sign of inco-ordination, it looks like a rapid series of contraction waves passing over the auricular walls.’’ McWilliam also tested the influence of vagal stimulation on AFL and found that ‘‘the fluttering movement of the auricles can be checked or arrested by the influence of the vagus nerve.’’ Most interestingly, McWilliam was perhaps the first to observe an association between cardiac mechanical and electrical activity in the maintenance of an arrhythmia: ‘‘The vagus influence appears to act by weakening the individual contractions [of the atria] to the point of invisibility.’’ It was clear from the MacWilliam’s work that AFL was a rapid ( 300 to 400 beats/min) yet a regular rhythm that could be sustained over the atria causing rapid and regular series of contractions. When Einthoven first introduced the ECG recording technique in man in 1906, he made an actual electrocardiographic recording of AFL. However, it was Sir Thomas Lewis 1909 who recorded a case in a dog of AFL alternating with atrial fibrillation (AF) that he called ‘‘auricular paroxysmal tachycardia.’’ It was only in 1911, that Jolly and Ritchie applied the term ‘‘auricular flutter’’ to the clinical arrhythmia in man and described the characteristic ‘‘sawtooth waves’’ in the inferior ECG leads. Two years later, Sir Thomas Lewis established the diagnostic criteria of electrocardiographic of AFL as ‘‘the restless, sawtooth baseline’’ now known as the F waves, which today are recognized as the principal criterion for the diagnosis of AFL in man. The recognition and the electrocardiographic description of this arrhythmia led to intense efforts to determine the mechanism of the AFL that still continues today. It was in 1920 that Lewis and his colleagues provided the first mechanistic insight into the reentrant excitation pattern causing AFL that in many ways is still valid today. Lewis’ original description of the AFL reads as follows: ‘‘A main excitation wave is propagated through the fluttering auricles via a narrow circular pathway embracing