Concealed ventricular extrasystoles.

AN apparently haphazard distribution of ventricular extrasystoles may not be so haphazard as it appears and indeed may mask an underlying regularity. We previously reported a case in which careful analysis uncovered a simple but remarkable phenomenon, namely, that the interectopic intervals always contained an odd number of sinus beats.1 This was explicable on the assumption that a bigeminal rhythm persisted in a concealed form. Since then we have observed this and related phenomena on many occasions. Our purpose here is to present the concept of "concealed extrasystoles," which has not been previously reported except for brief mention in our earlier communication.