How you prepare

Before your doctor decides if you need a pacemaker, you'll have several tests done to find out the cause of your irregular heartbeat. These could include:

• Electrocardiogram. In this noninvasive test, sensor pads with wires attached, called electrodes, are placed on your chest and sometimes your limbs to measure your heart's electrical impulses. Your heart's beating pattern can offer clues to the type of irregular heartbeat you have.

• Holter monitoring. Also known as an ambulatory monitor, a Holter monitor records your heart rhythms for an entire 24-hour period. Wires from electrodes on your chest go to a battery-operated recording device carried in your pocket or worn on a belt or shoulder strap.

  While you're wearing the monitor, you'll keep a diary of your activities and symptoms. Your doctor will compare the diary with the electrical recordings to try to figure out the cause of your symptoms.

• Echocardiogram. This noninvasive test uses harmless sound waves that allow your doctor to see your heart without making an incision. During the procedure, a small instrument called a transducer is placed on your chest. It collects reflected sound waves (echoes) from your heart and transmits them to a machine that uses the sound wave patterns to compose images of your beating heart on a monitor.

  These images show how well your heart is functioning, and recorded pictures allow your doctor to measure the size and thickness of your heart muscle.

• Stress test. Some heart problems occur only during exercise. For a stress test, an electrocardiogram is taken before and immediately after walking on a treadmill or riding a stationary bike. In some cases, an echocardiogram or nuclear imaging may be done.

  Other types of treadmill exercise tests also can be done to evaluate your heart, including an oxygen consumption test that measures how much oxygen your body is using.