Patient Basics: Holter Monitor and Event Monitor

A Holter monitor is a small, battery-powered ECG (EKG) recorder that you wear for 1 to 2 days, or sometimes up to 2 weeks, to record every heartbeat. An event monitor is worn for up to 30 days and saves your heart rhythm when you have symptoms or when it senses a problem. Both catch rhythm problems that come and go and may not show up during a short ECG at the doctor’s office.

Key points

• These heart monitors help find the cause of a racing or fluttering heartbeat, dizziness, or fainting.
• A Holter monitor records nonstop for a short time. An event monitor covers weeks, so it’s better for symptoms that happen only now and then.
• Wearing one is painless. The main problem is itchy skin under the sticky pads.
• Keep a diary of what you feel and what you’re doing. It helps your doctor match symptoms to your heart rhythm.
• A monitor records your heart but doesn’t treat it. Call 911 for chest pain or fainting, even while wearing one.

Why a heart monitor is used

A regular ECG records the heart’s electrical signals for about 10 seconds. If your symptoms come and go, that short window can easily miss the problem. Your doctor may suggest a portable monitor to:

• Find the cause of palpitations (a pounding, fluttering or skipping heartbeat)
• Look for a rhythm problem behind dizziness, lightheadedness or fainting
• Check for atrial fibrillation (AFib), an irregular rhythm that raises the risk of stroke, including after a stroke with no clear cause
• See how well heart rhythm medicine or a pacemaker is working
• Check your heart rhythm after a heart attack or heart surgery

Holter monitor vs event monitor

The right device depends on how often your symptoms happen.

• Holter monitor. Several sticky pads (electrodes) on your chest connect by thin wires to a recorder about the size of a deck of cards. It records every beat for 24 to 48 hours. Best for symptoms that happen daily.
• Patch monitor. A single wireless patch, stuck to the upper left chest, records every beat for up to 14 days. Many doctors now use these in place of a wired Holter.
• Event monitor. You wear it for up to 30 days. Most types record all the time but save only the stretch around the moment you press a button, plus any abnormal rhythm the device detects on its own. Some older types are held to the chest only when you feel symptoms.
• Mobile cardiac telemetry (MCT). A 30-day monitor that sends your rhythm to a monitoring center over a cell signal. Staff can alert your doctor about a serious rhythm within minutes.
• Implantable loop recorder. A tiny device, about the size of a USB stick, placed just under the skin of the chest through a small cut. It can record for about 3 years and is used when symptoms are rare.

Some smartwatches can record a one-lead ECG and spot AFib. They can be useful, but they don’t replace a medical monitor when your doctor needs a full record.

Getting ready for a Holter monitor

• Shower or bathe beforehand, since you may not be able to get the device wet.
• Don’t put lotion, oil or powder on your chest that day. The pads stick better to clean, dry skin.
• A technician may shave small patches of chest hair and lightly rub the skin.
• Wear a loose, button-front top.
• Bring a list of your medicines.

Wearing a Holter monitor or event monitor

A technician places the pads and shows you how the device works. Fitting it takes about 15 minutes. Then you go home and carry on as usual. Staying active is helpful, because it shows how your heart handles daily life.

• Keep a diary. Write down the time and what you felt (skipped beats, dizziness, chest discomfort) and what you were doing. Many devices also have an app or a button to mark symptoms.
• Press the button on an event monitor each time you have symptoms. Some devices send the recording through a phone app or a home base unit.
• Keep it dry unless you’ve been told it’s water resistant. Many patch monitors allow a quick shower.
• Keep pads in place. If one comes loose, press it back down or replace it as shown.
• Avoid strong magnets, metal detectors and electric blankets, which can disturb the signal. Keep your phone a few inches from the device.

Afterward and possible risks

You return the device in person or mail it back. Heart monitors are very low risk. The adhesive can leave red, itchy skin for a few days, and some people react to it. Tell the clinic if you’ve had a skin reaction to tape before. An implantable loop recorder carries a small risk of infection or bruising where it was placed.

Your results

A specialist reviews the recording, which can take 1 to 2 weeks. If a monitoring service sees a dangerous rhythm, someone will call you or your doctor right away. Common findings include:

• A normal rhythm, even during symptoms. This helps rule out a heart cause.
• Extra beats from the upper or lower chambers (PACs or PVCs). These are very common and often harmless.
• Atrial fibrillation or another fast rhythm, such as supraventricular tachycardia (SVT)
• A slow heart rate or pauses, which may point to a need for a pacemaker

When to call your doctor

• Your skin blisters or a rash spreads under the pads
• The device stops working or keeps showing an error
• Your symptoms change or get worse

Call 911 for chest pain or pressure, fainting, severe shortness of breath, or a fast heartbeat with dizziness. Don’t wait for the monitor results.

Common questions about Holter monitors

Can I shower with a Holter monitor?

Usually not with a wired Holter monitor, because water can damage the recorder. A sponge bath that keeps the chest dry is fine. Many patch monitors and some event monitors are water resistant and allow a short shower. Ask the technician what your device allows.

Can I sleep with a heart monitor on?

Yes, and you should. Nighttime recording can show slow rhythms or pauses that happen only during sleep. Sleep in any position that’s comfortable. Keep the recorder on the bed beside you or clipped to your clothes so the wires don’t pull on the pads.

Does a Holter monitor check blood pressure?

No, a Holter monitor records only heart rhythm. A separate device called an ambulatory blood pressure monitor checks blood pressure over 24 hours with a cuff on your arm. Your doctor may order both if you have dizziness or fainting.

Can a Holter monitor detect a heart attack?

Not reliably. It’s built to find rhythm problems, not blocked arteries. A heart attack needs a 12-lead ECG and blood tests in an emergency department. If you have chest pain while wearing a monitor, call 911 right away.

Questions to ask your doctor

• Which type of monitor is best for my symptoms, and why?
• How long will I wear it?
• Can I exercise, shower or swim with it?
• Who will call me if it records something serious?
• When and how will I get the results?

Learn more

• Holter monitor (24h) (MedlinePlus, U.S. National Library of Medicine)
• Cardiac event monitors (MedlinePlus, U.S. National Library of Medicine)

This guide is general information and doesn’t replace advice from your own doctor. Last updated October 2026.