How are heart rhythm disorders diagnosed?

The mainstay of diagnosis remains the EKG and heart rhythm monitoring. These are often done immediately in the ambulance or upon arrival in the emergency department. Unfortunately, in many patients, the palpitations or symptoms have resolved, and no acute rhythm abnormalities can be found.

Depending on the associated symptoms and the history, observation and monitoring of the heart may occur in hospital or as an outpatient. In patients who are syncopal, meaning that they passed out, and it cannot be explained by a benign diagnosis like vasovagal syncope, admission to the hospital often occurs. Those patients with chest pain and shortness of breath may also be admitted to evaluate their heart; otherwise, monitoring devices that can measure heart rates and rhythms for 24 or 48 hours or longer (up to one month or more) are used. In some instances, rhythm identification is elusive and may take months or years to capture and identify.

If the rhythm is known, then tests to identify potential causes may be done. These are dependent on the specific rhythm abnormality and can range from blood tests to lung evaluations to echocardiograms and electrophysiologic testing.

source: medicinenet