Ventricular ectopic beats with exit block: a retrospective Holter monitor study.

A retrospective study was conducted to define the incidence of ventricular ectopic beats with exit block (concealed extrasystoles). Of 904 Holter recordings, 92 were admitted for study on the basis of sufficient ventricular ectopic beats on rhythm strips. Concealed bigeminy conforming to the equation of S = 2n - 1 (where S = the interectopic sinus beat and N = any interger) was the most common and occurred in 42 of 92 (46%) Holters included in this study. Concealed trigeminy was observed in 12 of 92 (13%) studies. These Holters also showed ventricular ectopic beats strongly suggestive of parasystole with entrainment. Of 53 Holters reviewed for parasystole 12 were suggestive of, and five indicated this dysrhythmia. We conclude that: 1. Concealed extrasystoles are more common than previously appreciated. 2. Concealed bigeminy and trigeminy appear together and conversion may not always be associated with a change in heart rate. 3. Recognition of this dysrhythmia is uncommon mostly because of inadequate lengths of rhythm strips. 4. Parasystole with entrainment is suggested as a common dysrhythmia when frequent extrasystoles are present.