Doc fpund a hear murmur on my son who is five uears old. He is on ADHD medication. He never had one before. Could the concerta have caused it.

Echo. A heart murmur. A murmur is just noise. Sometimes serious problems cause a murmur many times a murmur is caused by normal flow. Patients often misctranslate what the dr. Tells them.Ask the doc what it means in your child.
No. It's probably an. Innocent murmur, meaning there's no structural heart disease. Think of hearing water rattle in pipes leading from an old-fashioned boiler. Sometimes my patients aren't quiet & still enough for me to hear a faint murmur till their meds are working well. A pediatric cardiologist can do echocardiogram to rule out a structural defect & an ekg to rule out an irregular heart rhythm, so you know it's ok.
No. In decades of practice I found that if I listen to a kid often enough I will eventually hear some extra heart sound (murmur).Most are innocent flow murmurs when detected at that age. Your doc could either decide it is or do a test to make sure. Concerta has no way to change the structure of the heart although it may trigger it to beat faster.