Concealed ventricular extrasystoles. A family of premature ventricular complexes with high spontaneous variability.

Background: The term concealed ventricular extrasystoles defines a phenomenon in which premature beats have a cyclical distribution and manifest after a predictable number of intervening sinus beats. The extent of its spontaneous variability as well as the stability of its orderly distribution, however, have not been defined yet. The aim of this study was to assess whether there is any difference between the variability of concealed ventricular extrasystoles and their allorhythmic patterns.

Methods: The distribution of premature ventricular complexes (PVCs) was evaluated in 39 patients with frequent monomorphic PVCs (> 1000/die) during a baseline 24-hour ambulatory monitoring electrocardiogram. Patients were divided into two groups: group A had evidence of concealed ventricular extrasystoles, while in group B PVCs were randomly distributed. All patients underwent a second ambulatory monitoring electrocardiogram within 30-360 days.

Results: The overall number of PVCs did not differ between the groups. Patients of group A showed a very high spontaneous variability (p = 0.006) between the first and the second ambulatory monitoring electrocardiogram, whereas significant differences were not observed among patients of group B.

Conclusions: Concealed ventricular extrasystoles are not casual and transient, but should be regarded as a marker of a "family" of PVCs that have the tendency either to maintain their orderly distribution for long periods or to disappear suddenly.