Can a Smartwatch Detect Atrial Fibrillation? When to Use Holter, Patch or an Implantable Loop Recorder (ILR)

Are you wondering whether your smartwatch can detect atrial fibrillation (AF) or rythm disorders? Or whether you might actually need an ILR (implantable loop recorder)? This guide gives you a clear, updated overview of what smartwatches can and cannot do when it comes to heart rhythm - and when a Holter monitor, patch monitor or ILR is the right choice. The article is written for patients, but is also relevant for GPs and healthcare professionals.

Are ILR useful in assessing palpitations?

A Practical Guide for Patients (and Clinicians)

Smartwatches and fitness trackers are now part of everyday life. Palpitations is a very common symptom and you can read more about what it may be, here. Many people ask: "Do I have atrial fibrillation?""Is this dangerous?""Should I get a loop recorder?"

In clinical practice, patients often request an ILR because they expect it to “solve” their palpitations. But the truth is more nuanced. Here is what you need to know.

1. How good are smartwatches at detecting atrial fibrillation?

A 2025 meta-analysis (26 studies, 17,349 participants) found the following:

• Sensitivity: ~95%

• Specificity: ~97%

• AUC: 0.97

In other words: Smartwatches distinguish AF from normal rythm very well in research settings.

There are differences between brands (Apple, Samsung, Withings), but all are now approaching medical-grade accuracy for AF screening. Both PPG (optical pulse) and single-lead ECG–based devices performed similarly in the analysis. They are excellent for screening, but cannot replace medical ECG diagnostics.

2. High accuracy does NOT mean zero problems

Even with good numbers, there are important limitations:

• False positives are more common in low-risk individuals → unnecessary worry and extra doctor visits

• Subclinical AF: We still do not know which short episodes truly require treatment

• Digital health anxiety: False alarms can increase fear, especially among younger users

• Older adults may misunderstand alerts or use the technology incorrectly

This is why smartwatch findings should always be reviewed by a clinician.

3. When is your smartwatch actually useful?

For patients:

A smartwatch is helpful if:

• You have symptoms (palpitations, dizziness)

• You can record an ECG during symptoms

• You use the watch as a supplement, not a replacement for medical evaluation

For healthcare professionals:

Smartwatch recordings can be useful:

• As documentation of rhythm irregularities

• To determine whether more formal monitoring is needed

But: Every recording must be interpreted critically, ideally by a clinician.

4. What about ILRs?

ILRs (implantable loop recorders) are most useful when:

• The patient has unexplained syncope

• After cryptogenic stroke, where they substantially increase AF detection

→ However: More AF detection does not automatically translate into fewer strokes or deaths.

For palpitations alone, ILRs often lead to overdiagnosis

• They record one ECG lead → P-waves are often unclear

• Cheaper, simple options (Holter, patch) often provide the same useful information

• Even when rhythm irregularities are recorded, the ILR cannot always clarify the exact arrhythmia mechanism

Therefore, ILRs should be reserved for specific high-risk cases, not routine palpitations.

5. Smartwatch vs ILR - competitors or complementary tools?

They may complement each other:

Smartwatches

• Screening

• Symptom correlation

• Low threshold for use

• Practical for long-term self-monitoring

ILRs

• Long-term monitoring for serious or rare events

• Detection of intermittent bradyarrhythmias or AF after stroke

  
  

A smartwatch may alert you that “something is happening”, but an ILR (or medical-grade ECG) is needed when treatment decisions depend on the diagnosis. However, even though an event is registered on a ILR, interpretation of rhythm disorder might still be challenging and uncertain. In practice, watches often undercount the pulse during premature beats, because these are not always detected by optical sensors.

6. What should patients know before asking for an ILR?

• An ILR is not more advanced than other EKG tools, it simply records over a much longer period, in one lead

• The procedure is minor, but still invasive

• It does not always provide answers, recorded rythms might still be difficult to interpret.

• Most patients with palpitations get sufficient information from a smartwatch + 1–2 weeks of external monitoring (Holter or patch)

• ILRs are very expensive and follow-up in clinical practice is quite demanding compared to the quality of information given by these device, particularly in case of palpitations.

  
  

7. Summary for 2025

Smartwatches

• High AF detection accuracy in studies

• Useful for screening and symptom documentation

• Findings must be confirmed with medical ECG

External monitoring (Holter/patch)

• First-line choice for palpitations

• Non-invasive, high-quality data

ILR

• Most useful for:

  • Unexplained syncope

  • Cryptogenic stroke

• Not first choice for isolated palpitations

  
  

Bottom line: A thorough clinical evaluation and a 12-lead ECG during symptoms remain the gold standard. Monitoring should be chosen based on symptoms, risk, and how the findings will influence treatment.

Frequently Asked Questions (FAQ)

Can my smartwatch detect atrial fibrillation?

Yes, modern smartwatches (Apple Watch, Samsung Galaxy Watch, etc.) have high accuracy in studies.They can detect irregular rhythms and record ECGs. But findings must always be reviewed and confirmed by a clinician.

Should I get an ILR if I have palpitations?

Not necessarily. ILRs are most useful for unexplained fainting or stroke of unknown cause.For palpitations alone, a smartwatch or 1–2 weeks of external monitoring is usually enough.

What’s the difference between a smartwatch and an ILR?

A smartwatch monitors your rhythm without any procedure. An ILR is a small implant placed under the skin that monitors your rhythm continuously for months or years. It is used only in select high-risk situations.

Can my smartwatch give false alarms?

Yes. Especially in healthy young users, normal rhythm variations can be misinterpreted as AF.This can lead to unnecessary worry, which is why confirmation is essential.

Why do I need a doctor when the watch says “possible AF”?

A smartwatch is a warning system, not a diagnostic tool. To decide whether you need treatment (for example, blood thinners), a doctor must assess the rhythm and your overall risk.