A test with a Holter monitor is safe, painless and affordable, it allows the doctor to obtain a detailed record of the heart rate for a prolonged period (24 to 48 hours during normal activity), to check the diary with the Holter record helps the doctorto diagnose problems with the heart rhythm.It is usually done after a traditional study to assess the heart rate (electrocardiogram), especially if the doctor was unable to obtain sufficient information about the state of the heart by means of the electrocardiogram.