What Can a 24-Hour ECG Monitor Reveal About Palpitations?

Published: 2 October 2026 · Next review due: 2 October 2027

Palpitations — the awareness of your own heartbeat, whether as a flutter, a thud, a racing sensation, or a missed beat — are among the most common reasons people seek a cardiac assessment. In many cases, they have a benign cause, such as caffeine, stress or tiredness. In others, they may reflect an underlying heart-rhythm disturbance that warrants further investigation. A 24-hour ECG monitor is one of the most practical tools for capturing what your heart is doing during everyday life, when symptoms are most likely to occur.

Quick Answer: A 24-hour ECG monitor — also called a Holter monitor — continuously records your heart's electrical activity over a full day and night. It can detect rhythm irregularities that may not appear on a standard resting ECG, including some types of arrhythmia. However, not every cause of palpitations will be captured within a single 24-hour period, and a normal result does not rule out every possible heart-rhythm condition. Whether this test is appropriate depends on your individual symptoms, history and clinical findings.

In summary, a 24-hour ECG monitor can:

• Record continuous heart-rhythm data during normal daily activity
• Detect intermittent arrhythmias that may be missed on a brief resting ECG
• Identify patterns such as ectopic beats, atrial fibrillation, or episodes of fast or slow heart rate
• Correlate symptoms with rhythm changes when the wearer keeps a symptom diary

It cannot:

• Assess the structure of the heart (an echocardiogram is used for this)
• Guarantee detection of an arrhythmia that did not occur during the recording period
• Provide a standalone diagnosis without clinical interpretation

What Is a 24-Hour ECG Monitor?

A 24-hour ECG — short for electrocardiogram — monitor is a small, portable device worn close to the body that records the electrical signals produced by your heart continuously over 24 hours. It is sometimes called a Holter monitor, after the scientist who developed the technology in the 1960s.

Unlike a standard resting ECG, which records only a brief snapshot of heart activity — typically around 10 seconds — a Holter monitor captures rhythm data throughout an entire day and night. This is important because many arrhythmias are intermittent, appearing only at certain times, during physical activity, after meals, at rest, or during periods of stress or sleep.

Wearing the monitor involves small adhesive electrodes placed on the chest, connected by wires to a recording device clipped to a belt or placed in a pocket. It is lightweight and designed to be unobtrusive, allowing you to carry out most normal daily activities. You are typically asked to keep a written diary during the recording period, noting the time and nature of any symptoms you experience. This diary is used alongside the recorded trace when a clinician reviews the results.

For those whose symptoms occur less frequently, longer-duration monitors — such as 48-hour, 72-hour or seven-day recorders — may be considered. In some cases, a longer-term implantable loop recorder may be discussed. The most appropriate monitoring duration depends on symptom frequency and clinical assessment.

Information about the different types of ambulatory ECG monitors used to investigate heart-rhythm symptoms is also published by Cardiologist London, which provides educational resources on a range of cardiovascular investigations.

What Can It Detect? Understanding Common Findings

When a cardiologist or cardiac physiologist reviews a 24-hour ECG trace, they are looking for any deviation from a normal, regular heart rhythm. Several findings can emerge from this analysis.

Ectopic Beats

One of the most frequently detected findings is ectopic beats — heartbeats that occur earlier than expected in the normal rhythm cycle. These can originate from the upper chambers of the heart (atrial ectopics) or the lower chambers (ventricular ectopics). They are responsible for the familiar sensation of a “skipped beat” or sudden thud in the chest, often followed by a short pause and then a stronger beat. Ectopic beats are extremely common and, in many people with no underlying heart disease, are considered benign. However, their frequency and pattern should be assessed in context.

Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained heart-rhythm disturbance seen in clinical practice. It causes the upper chambers of the heart to beat chaotically rather than in an organised rhythm, resulting in an irregular and sometimes fast heart rate. Symptoms include palpitations, breathlessness, fatigue and light-headedness — though some people experience no symptoms at all. Because AF can come and go (paroxysmal AF), a 24-hour recording has a meaningful chance of capturing an episode if one occurs during the monitoring period. Early identification of AF is clinically relevant because it is associated with an increased risk of stroke and requires assessment and management.

Cardiologist London provides further reading on heart palpitations and when they may require specialist assessment, including information about how arrhythmias are investigated.

Supraventricular Tachycardia (SVT)

SVT is a group of conditions causing episodes of rapid heart rate originating above the ventricles. Episodes can start and stop abruptly and may cause a racing heart, dizziness, breathlessness or chest discomfort. A 24-hour monitor can capture an SVT episode if it occurs during the recording window.

Bradycardia and Pauses

Ambulatory monitoring can also identify episodes of an unusually slow heart rate (bradycardia) or pauses in heart-rhythm activity that may be responsible for symptoms such as light-headedness, near-fainting or blackouts.

Normal Variation

It is important to understand that many recordings show findings that fall within normal variation — particularly in younger, otherwise healthy individuals. A clinician will interpret results in the context of your specific symptoms, medical history and any other investigations.

When Should Palpitations Be Assessed by a Clinician?

Palpitations do not always signal a serious problem, but there are patterns that merit a clinical review rather than simply monitoring at home.

You should seek a medical assessment if palpitations:

• Occur frequently or are becoming more regular over time
• Last for a prolonged period rather than a brief moment
• Are accompanied by breathlessness, chest discomfort, dizziness or light-headedness
• Cause you to feel faint or result in loss of consciousness
• Occur during exercise or exertion
• Are associated with a family history of heart disease or sudden cardiac events
• Cause significant anxiety or affect your daily quality of life

A standard resting ECG is often a first step, but because many arrhythmias are intermittent, a 24-hour or longer-duration monitor may provide a more informative picture.

If you are unsure whether your symptoms warrant assessment, NHS 111 can advise on the appropriate next step.

What Happens After the Recording?

Once the monitoring period is complete, the device is returned and the recorded data is analysed. This process can involve reviewing hundreds of thousands of individual heartbeats. Modern analysis software assists with identifying rhythm abnormalities, but clinical interpretation by a trained professional remains essential.

Results are typically reviewed in the context of:

• The symptom diary you kept during monitoring
• Your medical history and any existing conditions
• The findings of other investigations, such as a resting ECG, blood tests or echocardiogram
• Any relevant risk factors, including age, blood pressure and family history

A normal 24-hour ECG result is useful information, but it does not exclude every possible heart-rhythm condition — particularly those that occur infrequently. If symptoms persist despite a normal result, a clinician may recommend a longer monitoring period or alternative investigations.

Cardiologist London provides educational information about what a standard electrocardiogram test involves and when it is used, which may be useful for readers wanting to understand how these assessments are used in specialist practice.

Are There Other Investigations That Might Be Considered?

A 24-hour ECG monitor is a valuable tool, but it is one of several investigations that may be relevant when palpitations are assessed. Depending on the clinical picture, other tests might include:

• Resting 12-lead ECG — a brief recording providing a baseline rhythm trace
• Echocardiogram — an ultrasound scan of the heart assessing its structure and function, which can identify conditions such as valve disease or cardiomyopathy
• Blood tests — to check for thyroid dysfunction, anaemia, electrolyte imbalances or other factors that can contribute to palpitations
• Exercise stress test — to assess heart-rhythm response and any ischaemic changes during exertion
• Event recorder or loop recorder — for infrequent symptoms that are unlikely to be captured during a short monitoring period
• Implantable loop recorder — a small device inserted under the skin for longer-term monitoring, typically reserved for unexplained syncope or very infrequent episodes

Not every patient requires all of these tests. The choice of investigation depends on the nature of the symptoms, the clinical findings and the overall assessment of individual risk. A clinician will advise on the most appropriate pathway.

Supporting Your Heart Health

Whilst awaiting assessment or after receiving results, evidence-based lifestyle measures support long-term cardiovascular health. These include:

• Reducing caffeine and stimulants, which are known to increase the frequency of ectopic beats in some individuals
• Limiting alcohol, which can trigger episodes of atrial fibrillation and other rhythm disturbances
• Maintaining a healthy weight, as excess weight is associated with higher risk of AF and other cardiovascular conditions
• Managing stress and sleep, both of which influence heart-rhythm regulation
• Not smoking, given the well-established cardiovascular risks of tobacco
• Staying physically active in line with general guidance, unless a clinician advises otherwise based on your specific findings

These are general population-level measures. Do not change prescribed medication or begin a new exercise programme without advice from the clinician responsible for your care.

When to Seek Emergency Help

Some symptoms associated with the heart require immediate emergency care rather than routine clinical assessment.

Call 999 immediately if you experience:

• Sudden chest pain or pressure that does not settle
• Pain spreading to the arm, jaw, neck, back or stomach
• Chest discomfort combined with sweating, nausea or breathlessness
• Sudden severe breathlessness
• Collapse or loss of consciousness
• Sudden facial weakness, arm weakness or difficulty speaking

Do not drive yourself to hospital if you have these symptoms.

Frequently Asked Questions

Will I need to stay in hospital to wear a 24-hour ECG monitor?

No. A Holter monitor is worn at home during your normal daily routine. Electrodes are attached at the start of the monitoring period, and you return the device once the recording is complete. You can continue most everyday activities whilst wearing it, though you should avoid getting the device wet.

Does the monitor record what I am doing as well as my heart rhythm?

The device records your heart's electrical activity only. You are asked to keep a written symptom diary noting times and descriptions of any symptoms or activities. This diary is compared with the rhythm trace during analysis to see whether symptoms correlate with any rhythm changes.

What if my palpitations did not occur during the recording period?

This is a common outcome, particularly for infrequent symptoms. A normal result in this context means no arrhythmia was detected during that recording window — it does not exclude every possible rhythm condition. Your clinician may discuss whether a longer monitor, an event recorder, or alternative investigations are appropriate.

Can a 24-hour ECG detect atrial fibrillation?

It can detect AF if an episode occurs during the monitoring period. Because paroxysmal AF comes and goes, a single 24-hour recording may not capture every episode. Longer-duration monitoring or repeated recordings can increase the detection rate in those with suspected but unconfirmed AF.

Are there any risks associated with wearing a Holter monitor?

The monitor itself is non-invasive and carries no significant risk. Some people experience mild skin irritation from the adhesive electrodes, particularly those with sensitive skin. This is temporary and resolves once the electrodes are removed.

Do I need a referral to have ambulatory ECG monitoring?

In the NHS, a GP referral is the usual route to ambulatory monitoring. In a private setting, you can typically discuss your symptoms directly with a cardiologist, who will advise on the most appropriate investigations based on your history and clinical assessment. If you are considering a private specialist opinion, confirm current referral arrangements directly with the relevant provider.

Further Cardiology Information

At My Heart Clinic, we offer a range of cardiovascular services for patients seeking assessment and investigation of heart-related symptoms. Please contact us directly to confirm current service availability and to discuss whether an appointment may be appropriate for your circumstances.

Readers may also find it useful to consult Cardiologist London, an independent private cardiology clinic led by Dr Ravi Assomull at Harley Street, offering integrative cardiac assessment and ambulatory monitoring. You can read more about its private cardiology assessment services.

This article provides general information and does not constitute individual medical advice, diagnosis or treatment. Cardiovascular symptoms can have several possible causes and should be assessed according to individual circumstances. Seek advice from an appropriate healthcare professional if symptoms persist or worsen. Call 999 immediately if you may be experiencing a heart attack, stroke or another medical emergency.