Cardiac test · Clinically reviewed
Ambulatory ECG monitoring, from 24-hour Holter to 14-day patch monitors and implantable loop recorders.
A wearable ECG monitor records the heart rhythm continuously for 24 hours to 14+ days. Used to diagnose arrhythmias, palpitations, unexplained syncope and atrial fibrillation. Modern patch monitors (Zio) and implantable loop recorders capture events that traditional 24-hour Holters miss.
Why trust this guide
- 01
Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
- 02
Sourced, not summarised
Every claim is checked against NICE, ESC or a peer-reviewed source you can see at the end.
- 03
Updated for 2026
Reflects current UK and European guidance on ambulatory ECG selection, duration and interpretation.
Key facts
Ambulatory ECG at a glance.
The essentials, in plain English — what it is, which device fits which question, and what a modern report can tell you.
-
What it is
Continuous ambulatory ECG recording — a wearable monitor that captures every heartbeat outside the clinic.
-
Device options
24-hour Holter, 7–14 day patch monitor (such as Zio), or an implantable loop recorder for months to years.
-
Diagnostic yield
Yield rises with recording duration — longer monitoring picks up more paroxysmal arrhythmias.
-
Patch vs Holter
Modern patch monitors (Zio) are more sensitive than a 24-hour Holter for infrequent events.
-
Loop recorder
An implantable loop recorder is used for infrequent, high-risk symptoms — including unexplained syncope.
-
Symptom diary
Integrated with a patient symptom-diary so palpitations and dizziness can be correlated with the rhythm.
How it works
From consultation to a reported trace.
The steps a UK cardiology service will normally follow, in order — so you know what to expect and why.
Phase 1 · Setup
Consultation, device selection and fitting
Phase 2 · Wearing
24 hours to 14+ days of continuous recording
Phase 3 · Report
Upload, analysis and cardiology report
- 01
Setup
Cardiology consultation
A referral or private cardiology assessment establishes the clinical question the monitor needs to answer.
- 02
Setup
Select the right device
Holter, patch monitor or implantable loop recorder — chosen for how often symptoms occur and the level of risk.
- 03
Setup
Skin prepared and electrodes applied
The chest is cleaned, electrodes or the patch are positioned and secured for the full recording period.
- 04
Wearing
Wear for the prescribed duration
Normal daily activity is encouraged — exercise, sleep and routine, so any triggers can be captured.
- 05
Wearing
Symptom diary maintained
Palpitations, dizziness, chest discomfort and syncope are logged with the exact time, for later correlation.
- 06
Report
Device returned or uploaded
A Holter is returned to the clinic; patch monitors post back for analysis; loop recorders transmit wirelessly.
- 07
Report
Cardiology report within 5–7 days
A consultant cardiologist reviews the trace and issues a written report with a clear next step.
Typical end-to-end: 1–3 weeks depending on the device chosen.
What it shows
The rhythms an ambulatory ECG is designed to catch.
Ambulatory monitoring exists to answer one question — what is the heart actually doing when the symptom happens.
-
Atrial fibrillation
The single most important arrhythmia to catch — often paroxysmal and missed on a resting ECG.
-
Supraventricular tachycardia
Sudden-onset regular fast rhythms — captured with symptom correlation for ablation planning.
-
Ventricular ectopy burden
Quantifies how often the ventricle fires early — clinically important above roughly 10 %.
-
Non-sustained ventricular tachycardia
Short runs of ventricular tachycardia — a marker of structural heart disease that needs review.
-
Sinus pauses and bradycardia
Long pauses or a slow rate at rest — relevant if paired with dizziness, presyncope or syncope.
-
Heart block
Second-degree Mobitz II or third-degree AV block — often an indication for pacing.
-
Symptom-rhythm correlation
The whole point of ambulatory ECG — matching the diary entry to what the heart was actually doing.
-
Red flag: sustained VT or complete heart block with syncope — urgent cardiology admission
Do not wait for a routine slot. Go to A&E or call 999.
Next steps
What follows the report.
The management options a cardiologist chooses from, matched to what the monitor actually found.
-
Reassurance if normal
A clean, symptom-negative trace is a diagnosis in itself — often the reassurance patients need.
-
Rate control (AF)
Beta-blocker or rate-limiting calcium-channel blocker to control the ventricular rate in atrial fibrillation.
-
Rhythm control (AF)
Anti-arrhythmic drugs or cardioversion where sinus rhythm is the goal — chosen on symptom burden and AF pattern.
-
Anticoagulation per CHA₂DS₂-VASc
Stroke-prevention anticoagulation in AF, guided by the CHA₂DS₂-VASc risk score.
-
Electrophysiology referral
Specialist review for SVT, pre-excitation, unexplained syncope or complex ventricular arrhythmia.
-
Cardiac ablation
Catheter ablation for symptomatic AF, SVT and selected ventricular arrhythmias — often definitive.
-
Pacemaker
For symptomatic bradycardia, sinus pauses with syncope, and high-grade AV block.
-
Implantable defibrillator (ICD)
For sustained VT, resuscitated cardiac arrest and high-risk cardiomyopathy — a device that treats life-threatening rhythms.
What this guide is based on
The sources behind every claim on this page.
UK and European guidance and specialist society standards, current at the time of last review.
Key references
Guidelines and standards we relied on.
A quiet reminder
This guide is for information, not medical advice.
Your cardiologist knows your history and can tell you which parts apply to you. If you have new palpitations, syncope or chest pain, seek assessment.
-
National Institute for Health and Care Excellence (NICE). Atrial fibrillation: diagnosis and management (NG196).
-
European Society of Cardiology. Guidelines on the management of cardiac arrhythmias.
-
American Heart Association. Ambulatory ECG monitoring — scientific statement.
-
British Cardiovascular Society. Standards for ambulatory ECG reporting.
Red flags
When an ambulatory ECG finding becomes an emergency.
Most reports are reassuring. These are the findings — and the personal-history triggers — where you should act today, not next week.
-
Sustained ventricular tachycardia
A broad-complex tachycardia lasting more than 30 seconds — a life-threatening rhythm.
-
Complete heart block
Third-degree AV block — especially with symptoms — needs urgent pacing assessment.
-
Pause > 3 seconds with syncope
A prolonged pause paired with loss of consciousness is a pacemaker indication until proven otherwise.
-
New AF with stroke symptoms
FAST signs alongside newly documented atrial fibrillation — call 999.
-
Wolff-Parkinson-White with AF
Pre-excited AF can degenerate to ventricular fibrillation — urgent electrophysiology review.
-
Long QT with syncope
QT prolongation and blackouts point to torsades risk — urgent cardiology assessment.
-
Brugada pattern
A type-1 Brugada ECG pattern — needs specialist inherited-arrhythmia review.
-
Congenital heart disease with arrhythmia
Any new rhythm in adult congenital heart disease needs specialist input.
-
Family history of sudden cardiac death
A first-degree relative with sudden cardiac death under 40 — screening and specialist review are indicated.
Frequently asked
Everything we get asked about ambulatory ECG.
Quick answers on device choice, wearing time, reporting and what happens if the monitor catches a dangerous rhythm.
-
What is an ambulatory ECG?
A wearable ECG monitor that records the heart rhythm continuously outside the clinic — from 24 hours (Holter) up to 14 days (patch monitor), or months to years (implantable loop recorder).
-
Which is better — a 24-hour Holter or a Zio patch?
For infrequent symptoms, a 7–14 day patch monitor such as Zio is more sensitive than a 24-hour Holter because it records for far longer. For daily symptoms, a Holter is often enough.
-
When is an implantable loop recorder used?
For infrequent, high-risk symptoms — most commonly unexplained syncope — where months or years of monitoring are needed to catch the event.
-
Can I shower or exercise with a patch monitor?
Most modern patch monitors are water-resistant and designed for normal daily activity, including light exercise. Follow the specific device instructions given at fitting.
-
How quickly will I get the report?
A cardiology-reported ambulatory ECG report is typically available within 5–7 days of the device being returned or uploaded.
-
What if the monitor shows a dangerous rhythm?
Sustained ventricular tachycardia or complete heart block with syncope are cardiology emergencies. The reporting clinician will arrange urgent hospital assessment — you should not wait for a routine appointment.
Related tests
Looking for a different test?
-
24-hour ABPM
Ambulatory blood-pressure monitoring — the vascular equivalent.
Learn more -
Cardiac MRI
A detailed look at heart muscle and function.
Learn more -
Cardiopulmonary exercise test
CPET — exercise capacity and the heart under load.
Learn more -
All tests
Browse every test and procedure we cover.
Learn more -
Hypertension
Related condition guide.
Learn more -
Atrial Fibrillation
Related condition guide.
Learn more -
Coronary Angioplasty
Related treatment option.
Learn more -
Coronary Artery Disease Treatment
Related treatment option.
Learn more
In practice, in London
How ambulatory ECG tends to unfold when you go private
With ambulatory ECG, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. The wait for ambulatory ECG on the NHS depends heavily on where you live and how urgently the referral is graded. Central and West London private clinics can normally book within a week, with imaging or a procedure slot to follow shortly after. It’s worth being honest about the reason for going private: usually it’s time, not a fundamentally different test.
Once you’re in the private system for ambulatory ECG, the pace picks up noticeably. Consultant slots run to time, imaging is usually available in the same building or a short walk away, and the report comes back typed and detailed. It’s the coordination that tends to feel different — one person on the other end of the phone, not a switchboard. For ambulatory ECG specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
There are a lot of consultants in London who can technically handle ambulatory ECG. Fewer who do it week in, week out for the exact question you’re bringing. We spend most of our time working out which is which — and being straight when a different test or a different specialist would serve you better. Everything runs to CQC, GMC and Royal College standards; the choice is about fit, not floor.