title: [Occult ventricular bigeminy. Description of a case with extrasystole variable coupling separated by sinus beats in even or odd numbers].
abstract: We have analyzed an electrocardiogram showing many unifocal ventricular extrasystoles with wide variations of the coupling intervals. Ventricular bigeminy was frequent but in many instances more than one sinus beat occurred between two consecutive extrasystoles. In such a case the intervening sinus beats occurred indifferently both in odd and even numbers. Moreover, extrasystoles preceded by an even number of sinus beats had a relatively long coupling interval whereas extrasystoles that followed and odd number of sinus beats showed shorter coupling intervals. An opposite pattern of the coupling interval was observed with the extrasystoles that followed an interpolated premature ventricular depolarization. In such a case the coupling interval was long after an odd number of sinus beats and vice versa. This mechanism may be interpreted as due to concealed ventricular bigeminy caused by a ventricular ectopic focus which is surrounded by two different zones of block: a proximal zone of 2:1 block, and a distal one in which the block occurs irregularly. Unlike what appears in typical concealed bigeminy, characterized by only odd numbers of sinus beats between consecutive extrasystoles the intervening sinus complexes are indifferently in odd and even numbers. The constant relationship between the coupling interval and the number (odd or even) of sinus beats by which the extrasystole is preceded, allows us to recognize the presence of an atypical form of concealed bigeminy.
mesh_terms: D000368:Aged; D005117:Cardiac Complexes, Premature / Q000503:physiopathology*; D004562:Electrocardiography; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male
vernacular_title: Bigeminismo ventricolare occulto. Descrizione di un caso con extrasistoli a copula variabile separate da battiti sinusali in numero pari o dispari.