An ECG P-P interval difference greater than 120, that is, the difference between the longest P-P interval and the shortest P-P interval in the same lead, is greater than 0.12 seconds, suggesting the presence of sinus arrhythmia. The P-P interval, which is the distance between two P-waves in the same lead, is usually measured in seconds and is an important basis for calculating heart rate. In people with sinus arrhythmia, the P-wave to P-wave intervals will vary and may be more than 0.12 seconds apart when the ECG is performed. For people with sinus arrhythmia, it is important to analyze it in conjunction with other clinical manifestations to rule out abnormal heart rhythms caused by drugs, food, exercise, mental overstress, and other factors. For people with symptoms such as chest tightness, palpitations, dizziness, etc., it is necessary to carry out standardized treatment under the guidance of a doctor.