Dear Ms. Melisaa
thanks for writing to us.
A flutter /heartbeat which increases on exercise is likely to be a pulsation related to heart or blood vessels. this may be a normal rhythm which you are feeling (thin anxious individuals can feel a lot of pulsation in various body parts) or it can be something not normal. moreover since you have a heart murmur
, an abnormality must be ruled out. since this requires an examination, i would like you to see your doctor. you can revert back to us, once you had a consultation for further clarifications.