Atrial Dissociation and Uniatrial Fibrillation

Three cases of atrial dissociation are illustrated with electrocardiograms. The coexisting atrial rhythms observed in published cases permit us to offer a convenient classification. Two possible explanations of this rare phenomenon are discussed. ATRIAL dissociation has been repeatedly observed in the exposed heart of the experimental animal. There is no reason to believe that the phenomenon may not occur spontaneously in the human heart. The purposes of this communication are to present tracings and to draw attention to this little-discussed phenomenon and to include examples of what we have chosen to call uniatrial fibrillation. LITERATURE Numerous authors have claimed to demon-strate independent rhythms in the 2 atria. Hering ' in 1900 first recorded dissociation of the atria in the experimental animal, whereas Wenckebach ' in 1906 was first to report it in man. Neither of these authors illustrated his claim with published electrocardiograms. A number of these publications invite special comment. Schrumpf3 published the first il-lustrative electrocardiogram; his tracing ap-pears reasonably convincing, but Lewis,4 quite properly setting the sceptical pace for all subsequent critics, refused to accept it and pointed out that "it is necessary to be hyper-critical in dealing with exceptional curves of this kind, owing to the important conclusions which they would otherwise justify. " The 3 tracings published by Bay and Adams5 are further good examples of the double P-wave type. As an argument in favor of the reality of atrial dissociation in their cases, they pointed out that the secondary atrial waves in 2 of their records showed a phasic arrhythmia affecting the normal P waves. Condorelli's tracing of simultaneous fibrilla-tion and sinus rhythm6 affords excellent ex-perimental basis for clinical claims of uniatria