A good history and physical examination are helpful in finding the cause of the palpitations.
If the child has fainting along with the racing of the heart, this may indicate a ventricular tachycardia and should be evaluated by a physician right away.
Most children with palpitations will have a normal cardiac exam. If their exam is not normal, the patient may have a structural problem with the heart that may be causing the palpitations (i.e., hypertrophic cardiomyopathy).
The physical exam may also give clues as to the function of the heart, which may be strongly linked with the palpitations.
To diagnose the problem, an electrocardiogram while the patient is having the palpitations will be required. An electrocardiogram done during an office visit will usually not show the rhythm disturbance but will help to rule out any structural reason for the problem.
Portable monitors that record the heart rhythm nonstop over 24 hours (Holter monitor) are usually the most helpful to diagnose the rhythm.
If the doctor suspects the child has ventricular tachycardia, sometimes a more invasive electrophysiology study needs to be done in the cardiac catheterization laboratory to induce the fast heart beat under controlled conditions.
If the symptoms occur during exercise, an exercise test may be helpful in making the diagnoses.