<s>[INST] My 16 yr old son went to donate blood last week was declined because they said noticed irregular pulse went for sport physical today PA didn t noticed pulse irregular but a pulse of 104 did EKG said sinus rhythm was off but dr. Said that was normal. Yet scheduled him tomorrow for an echocardiogram so just curious what s going on [/INST] Hello, After going through your medical query I understand your concern and I would like to tell you that 104 pulse rate can be normal in 16 year depending on his physical activity, stress and physiological changes. If ECG is sinus then no need to worry. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Bhanu Partap, Cardiologist </s>