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Diagnostic Testing & Imaging


What is ambulatory rhythm monitoring?

Ambulatory rhythm monitoring uses a small portable electrocardiograph device to measure the electrical activity of your heart for an extended period of time.

How does ambulatory rhythm monitoring work?

The heart has its own electrical system that synchronizes the heart to contract in rhythm and pump blood. Every heartbeat creates a pattern of electrical activity that can be detected with an electrocardiogram device. Like an electrocardiogram in the clinic, the most common types of ambulatory rhythm monitoring use external leads (small patches that are attached to the skin) to record the electrical activity of the heart. More advanced ambulatory rhythm monitoring equipment may be implanted under the skin for long-term recording.

When ambulatory rhythm monitoring is prescribed, the patient is outfitted with a portable electrocardiograph device in the clinic and asked to keep a diary of certain activities while they are being monitored. This helps cardiologists connect symptoms and abnormal sensations to electrical abnormalities in the heart.

Types of ambulatory rhythm monitoring


There are different types of ambulatory rhythm monitoring that are used for specific heart conditions. Generally, different types of ambulatory rhythm monitoring can be described as either continuous monitoring, event monitoring, or loop recording.


Continuous Monitoring

Continuous monitoring uses an external portable electrocardiogram device called a Holter monitor. The device consists of 3 to 5 electrodes placed on the chest. The electrodes are attached to a cell-phone sized device that the patient carries with them throughout the duration of testing. The electrical activity of the heart is recorded for 24 to 48 hours and then reviewed by a cardiologist.


Event Monitoring (External Loop Recorders)

Like continuous monitoring, event monitoring uses an external portable electrocardiograph device, but only records the heart’s electrical activity when activated. Some devices activate automatically when they detect slow, fast, or irregular heart rates; other devices must be activated by the patient during a symptomatic event. When activated, data is either stored for later review or transmitted to a cardiologist.

Implantable Loop Recorders

An implantable loop recorder is a small device that is implanted in the chest just under the skin that records the electrical activity of the heart when activated. Depending on the device, it may be activated automatically when the device detects an irregular heart rate, or activated by the patient during a symptomatic event by placing an activator over the device.

Ambulatory Rhythm Monitoring

What is ambulatory rhythm monitoring used for?


After an initial electrocardiogram test, your cardiologist may want to monitor the electrical activity of your heart for a longer period of time to help make a diagnosis or guide treatment. Ambulatory rhythm monitoring may be used:


  • When cardiac symptoms are infrequent and do not occur during an electrocardiogram in the clinic

  • To determine the cause of a rapid, strong, or irregular heartbeat (palpitations)

  • To determine the cause of fainting or collapse (syncope)

  • To identify electrical disturbances in patients at risk for sudden cardiac death

  • To identify asymptomatic atrial fibrillation as a source of stroke

  • To evaluate the heart after a recent myocardial infarction (heart attack)

  • When monitoring the effects of drugs and interventions in atrial fibrillation


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[1] Zimetbaum, P., & Goldman, A. (2010). Ambulatory arrhythmia monitoring: Choosing the right device. Circulation, 122(16), 1629–1636.

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