My 7yo daughter has the same Reaction as you. Even a small dosage of Ritalin will set her heart racing. She takes intuniv in the evening but hasn’t helped with the rapid heart rate. Resting heart rate when taking Ritalin 5mg is between 125-167bpm. Her normal resting heart rate is around 70-80bpm. We have now stopped Ritalin and only taking Intuniv 2mg but it hasn’t helped with ADHD symptoms. Also looking for solutions. Dr is still puzzled.