Complete compensatory interval and incomplete compensatory interval are terms used on the electrocardiogram. A complete compensatory interval is defined as the time between 1 QRS wave group before and 1 QRS wave group after a premature beat in an ECG with a premature beat that is the same as the time between 3 QRS wave groups without a premature beat. In contrast, an incomplete compensatory interval is the time from 1 QRS waveform cluster before premature beats to 1 QRS waveform after premature beats, which is shorter than the time of 3 QRS waveforms without premature beats. Complete compensatory intervals are usually seen in ventricular premature beats, and incomplete compensatory intervals, are usually seen in atrial premature beats.