ECG on my 2 y.o. son revealed polytopic supraventricular extrasystoles. Holter analyses will be performed soon. In general, his behaviour is totally normal (no symptoms of fatigue, or other of any kind). No one in family with heart issues. I understand this is little information yet, but how much such ECG is common for 2 y.o. , and how much (in %) could it be a situation to worry about?

Summarized question: What does ECG showing polytopic supraventricular extrasystoles indicate?