Holter monitors sometimes are called continuous EKGs (electrocardiograms). This is because Holter monitors record your heart rhythm continuously for 24 to 48 hours.
A Holter monitor is about the size of a large deck of cards. You can clip it to a belt or carry it in a pocket. Wires connect the device to sensors (called electrodes) that are stuck to your chest using sticky patches. These sensors detect your heart's electrical signals, and the monitor records your heart rhythm.
Wireless Holter Monitors
Wireless Holter monitors have a longer recording time than standard Holter monitors. Wireless monitors record your heart's electrical activity for a preset amount of time.
These monitors use wireless cellular technology to send the recorded data to your doctor's office or a company that checks the data. The device sends the data automatically at certain times. Wireless monitors still have wires that connect the device to the sensors on your chest.
You can use a wireless Holter monitor for days or even weeks, until signs or symptoms of a heart rhythm problem occur. These monitors usually are used to detect heart rhythm problems that don't occur often.
Although wireless Holter monitors work for longer periods, they have a down side. You must remember to write down the time of symptoms so your doctor can match it to the heart rhythm recording. Also, the batteries in the wireless monitor must be changed every 1–2 days.
Event monitors are similar to Holter monitors. You wear one while you do your normal daily activities. Most event monitors have wires that connect the device to sensors. The sensors are stuck to your chest using sticky patches.
Unlike Holter monitors, event monitors don't continuously record your heart's electrical activity. They only record during symptoms. For many event monitors, you need to start the device when you feel symptoms. Some event monitors start automatically if they detect abnormal heart rhythms.
Event monitors tend to be smaller than Holter monitors because they don't need to store as much data.
Different types of event monitors work in slightly different ways. Your doctor will explain how to use the monitor before you start wearing it.
Postevent recorders are among the smallest event monitors. You can wear a postevent recorder like a wristwatch or carry it in your pocket. The pocket version is about the size of a thick credit card. These monitors don't have wires that connect the device to chest sensors.
To start the recorder when you feel a symptom, you hold it to your chest. To start the wristwatch version, you touch a button on the side of the watch.
A postevent recorder only records what happens after you start it. It may miss a heart rhythm problem that occurs before and during the onset of symptoms. Also, it might be hard to start the monitor when a symptom is in progress.
In some cases, the missing data could have helped your doctor diagnose the heart rhythm problem.
Presymptom Memory Loop Recorders
Presymptom memory loop recorders are the size of a small cell phone. They're also called continuous loop event recorders.
You can clip this event monitor to your belt or carry it in your pocket. Wires connect the device to sensors on your chest.
These recorders are always recording and erasing data. When you feel a symptom, you push a button on the device. The normal erase process stops. The recording will show a few minutes of data from before, during, and after the symptom. This may make it possible for your doctor to see very brief changes in your heart rhythm.
Autodetect recorders are about the size of the palm of your hand. Wires connect the device to sensors on your chest.
You don't need to start an autodetect recorder during symptoms. These recorders detect abnormal heart rhythms and automatically record and send the data to your doctor's office.
Implantable Loop Recorders
You may need an implantable loop recorder if other event monitors can't provide enough data. Implantable loop recorders are about the size of a pack of gum. This type of event monitor is inserted under the skin on your chest. No wires or chest sensors are used.
Your doctor can program the device to record when you start it during symptoms or automatically if it detects an abnormal heart rhythm. Devices may differ, so your doctor will tell you how to use your recorder. Sometimes a special card is held close to the recorder to start it.