These rhythm strips are from 2 different patients. In both there is group beating caused by atrial premature beats. In the upper strip, atrial bigeminy causes groups of 2 beats and in the lower strip, atrial trigeminy results in groups of 3. In each case, the diagnosis is relatively straight forward because the ectopic premature P waves, with wave forms that are clearly different than the non-premature sinus P waves, are quite easily recognized.