Symmetry, broken symmetry, and restored symmetry of apparent pure ventricular parasystole

Agustin Castellanos, Pedro Fernandez, Federico Moleiro, Alberto Interian, Robert J. Myerburg

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Previous reports dealing with the dynamics of "pure" parasystole using mathematic and electronic (pacing-induced) models, respectively, showed that a number of predictions emerged naturally from mathematic analysis.1,2 Therefore, it appeared of interest to determine whether they would also apply to a series of patients with clinical (apparently) "pure" ventricular parasystole who were monitored for relatively long periods of time. In contrast to previous studies, Glass et al1 had the ingenious idea of analyzing the number of sinus beats interposed between 2 consecutive manifest parasytolic beats. They observed that, with the rates being practically constant, a detailed mathematic description could be made using 2 parameters: the ratio of ectopic cycle length to sinus cycle length and the ratio of ventricular refractory period to sinus cycle length. From a correlation of these parameters 3 basic rules emerged: (1) There are at most 3 different values for the number of sinus beats in between parasystolic beats. (2) Only 1 of these values is odd. (3) The sum of the 2 lesser values is 1 less than the larger value.

Original languageEnglish (US)
Pages (from-to)256-259
Number of pages4
JournalThe American Journal of Cardiology
Issue number2
StatePublished - Jul 15 1991

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine


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