An isolated VEB which occurs without any compensatory pause between two normal sinus beats, but significantly alters the concurrent heart rate. The sequence appears as: "N_NVN_N", where N=Nomal Sinus Beat, V=VEB, and _= the regular R-R interval between the Normal Sinus Beats.

Interpolated VEB. Note the "concealed" condition (hidden P-wave) of the sinus originated beat immediatly following the Interpolated VEB))