Tests may include: Electrocardiogram (ECG or EKG): During an EKG, electrodes are placed on your chest to look at the rhythm and electrical activity. Holter monitor: This is a portable machine you wear for a few days to monitor and record your heart rhythm.  Echocardiogram: An echocardiogram is a non-invasive ultrasound test that provides a view of the heart as it works. Stress test: A stress test looks at your heart under exertion, either while exercising or receiving a special intravenous (IV) medication. Event monitor: This is a portable monitor you wear for a month. You can hit the record button when feeling heart palpitations or other symptoms.