How often must people get an electrocardiogram (ecg)?

Symptoms: One should get an ECG only when they have symptoms suggestive of heart problems: chest discomfort or pain, palpitations or shortness of breath. Otherwise, one can discover incidental findings that would lead to more (often inappropriate) tests.

ECG: Once you have a baseline ecg, you really only need others for changes in status. If nothing new appears to be going on to evaluate, you don't really need another one.

Depends on risk : Factors and underlying cardiac condition or new symptoms.