• Sensation of feeling the heart beat (palpitations)
• Light-headedness
• Fainting
• Shortness of breath
• Chest tightness
• Infants may have weight loss and failure to thrive

Additional symptoms that may be associated with this disease:

• Dizziness
• Breathing difficulty, lying down

An examination shows a heart rate of 100 to 180 beats per minute. Blood pressure is normal or low. There may be signs of poor circulation.

Tests that reveal M.A.T. include:

• ECG
• Continuous ambulatory monitoring (24-hour Holter monitor). For hospitalized patients, the heart rhythm is monitored 24 hours a day with telemetry.
• Long-term loop recorders: outpatients who may have M.A.T. not detected during a Holter monitoring session can receive these portable systems, which allow the person to trigger the recording if symptoms appear.
• Electrophysiologic study (EPS). If doubts persist about the the diagnosis, or if there are additional arrhythmias which can complicate diagnosis, your doctor may recommend an EPS. During an EPS, wires are inserted through your veins up to your heart to study the cardiac conduction system.