Hi My son is 4 yrs 4 months old i feel like he is having fast heartbeat when I touch his heart. i use to check his pulse it says 120 even he sit and watch tv and 140 when he is extremely active. i checked with the doctor he asked for echo and ECG. ECG how's sinus arrhythmia and right ventricular hypertrophy but in Echo everything is normal. Doctor said nothing to worry since echo didn't show any abnormality.. what should I do next .. should i not to worry about his fast heart beats or what should I do next.. kindly help