What could causes a heart murmur in an otherwise healthy 17yr. old?

Murmurs in youth: Healthy young people, especially athletic ones, often have benign heart murmurs. However, this is something that must be evaluated by a doc. A doc needs to hear the murmur, note where it is coming from and possibly do an ultrasound exam of their heart. Especially if this is a new murmur, you need to see your doc.

Could be normal: Thin young healthy teens can have turbulent blood flow heard as a murmur. Heart valve abnormalities can lead to murmurs, but are rare. Sometimes, if a teen is anemic, the increased heart rate from that will cause the murmur. Have the doctor listen carefully, and an echocardiagram may be needed. This is a painless, not invasive test which uses sound waves to look at the heart structure.