The normal standard for PNN50 is 4.4% to 29%. The normal reference range for PNN50 is 4.4% to 29%, beyond which PNN50 can be considered elevated, which can clinically suggest problems such as sympathetic or vagal balance disorders. PNN50 refers to the percentage of the total number of sinus beats on the electrocardiogram (ECG) in which the difference between neighboring NNs is greater than 50ms, and is a type of heart rate variability (HRV) index. It reflects the state of balance between sympathetic and vagal regulation and is an important test used clinically to prevent cardiovascular events. Therefore, it is important to seek professional help when abnormal results occur. To summarize, the normal standard range of PNN50 is 4.4%~29%, if this abnormality occurs, please consult a doctor in time.