Atrial premature beats can be analyzed at two levels. First, atrial premature beats are defined as early atrial excitation, which is manifested as early P waves on the ECG. If the early P wave is not followed by the QRS wave, it means that the atrial premature beats are not effectively transmitted to the ventricles and cause ventricular excitation, possibly because the early atrial premature beats happen to occur during the ventricular excitation non-excitation period, when the ventricles themselves are beating regularly. In other cases, there is already a conduction block between the atria and the ventricles, such as atrioventricular block, so that the premature beats cannot effectively excite the ventricles. For example, if there is a conduction block, but the ventricular rate is still around 60-100 beats/min, the hemodynamic disturbance is actually not significant. Pacemaker.