The occurrence of simultaneous independent paroxysmal tachycardias is regarded as extremely rare. It is not known, however, whether the incidence of double tachycardias is really low or only apparently so, owing to the difficulty of diagnosis because of superimposition of auricular complexes at a rapid rate on ventricular complexes. In a recent study at the Cook County Hospital we have encountered seven cases of dissociated paroxysmal tachycardias during a 10 month period. In six instances there was a paroxysmal ventricular tachycardia with a simultaneous independent paroxysmal supraventricular pacemaker. Of the supraventricular mechanisms, two were auricular tachycardia and four were auricular flutter. In the seventh case dissociated paroxysmal auricular and nodal tachycardias were present.
The occurrence of auricular fibrillation with ventricular tachycardia is not infrequent, but the incidence of auricular paroxysmal tachycardia or auricular flutter with ventricular (or nodal) tachycardia is rare. In 1930 Strauss,1 reviewing the literature, found 65