The vagus nerve
carries pain sensations to the brain from the heart. It also carries pain senstions to the brain from the esophagus
, portions of the stomach, intestines, lungs and the inside of the chest wall. If he is truly having pain "in his heart" then that pain could be coming from any of those organs. The brain can't tell the difference.
First, a 24-hour event monitor does not rule out serious heart disease
. He should have a much longer monitor with you keeping a good diary. If he has symptoms while the monitor is on, but the monitor shows no changes during those times, then you can be sure that the pain is not from an abnormal heart rhythm. Heart pain can also be from a structural problem rather than a rhythm problem. If his pain is truly heart pain then he should also have an electrocardiogram (EKG) and an echocardiogram
Second, most "heart pain" in kids, by a factor of about 20 to 1 is not heart pain at all, but rather a symptom of anxiety
(mainly normal, but sometimes not). I'd want to keep track of when the pain happened (e.g. before quizzes, before chores) and how you responded as parents (e.g. does he get special attnetion when his "heart" hurts).
Third, keep in mind the other organs attached to the vagus nerve. Might he have some acid reflux? Might he get gas pains or constipation? Might he have a lung disease like asthma? Is his problem with the chest wall lining (e.g. pleurisy
," which has a long name but is not at all serious)?
Check out familydoctor.org and click on "Find a doctor" on the left if you're looking for a qualified doctor who understands all of these conditions and will take you seriously.