Atrial fibrillation screening: pulse checks, ECGs and smartwatch alerts
Atrial fibrillation (AFib) is a common irregular heart rhythm in which the upper chambers quiver instead of contracting in an organized way, and you may not be aware of it. (MedlinePlus AFib) It raises the risk of blood clots and stroke. (NHLBI AFib) For adults without symptoms, the USPSTF found the evidence insufficient to recommend for or against screening. (USPSTF, 2022)
Are adults without symptoms screened?
- USPSTF (2022): for adults 50 and older without signs or symptoms of AFib and without a past stroke or TIA, the evidence is insufficient to weigh benefits against harms (I statement). Its review also looked at blood pressure cuffs, pulse oximeters, smartwatches and smartphone apps, and still did not find enough evidence. Clinicians use their judgement about whether and how to screen. (USPSTF, 2022)
- The pulse check is already routine: the USPSTF considers feeling the pulse part of usual care. (USPSTF, 2022) NHLBI says screening steps may be part of regular care if you are 65 or older or have other risk factors, and your provider may check your pulse for an irregular speed or rhythm even if you have no symptoms. (NHLBI AFib diagnosis)
- ACC/AHA (2023): screening has been studied mostly in people over 65; longer or repeated ECG recordings find more AFib, but it is not yet established that screening people at high risk improves stroke, embolism or survival outcomes. (ACC/AHA, 2023)
AFib becomes more common with age, from under 0.2% of adults younger than 55 to about 10% of those 85 or older. (USPSTF, 2022) The one-line summary of this, alongside other heart tests, is on heart screenings by age.
Possible harms: the USPSTF says an ECG or wearable monitor causes no significant harm in itself, but an abnormal result may cause anxiety, a misread result may lead to a wrong diagnosis and unnecessary treatment, treatment carries its own risks such as bleeding, and an ECG can turn up other findings, true or false, that lead to more tests. (USPSTF, 2022) More on this: false positives and overdiagnosis.
What each check involves
Screening can be a one-time check at a visit, or brief recordings repeated several times a day or week on a portable device. (USPSTF, 2022)
| Check | What it involves | Source |
|---|---|---|
| Pulse check | Your provider feels your pulse to find out how fast your heart is beating and whether the rhythm is irregular, and listens to your heart. The USPSTF counts feeling the pulse as part of routine care, not as a separate screening test. | NHLBI AFib diagnosis USPSTF, 2022 |
| 12-lead ECG | Sticky patches called electrodes on your arms, legs and chest record the heart's electrical activity while you lie still. An ECG may show AFib or atrial flutter. More on the test: ECG at a checkup. | MedlinePlus ECG MedlinePlus AFib |
| Holter monitor | Patches on your chest are wired to a small recorder you carry for 24 to 48 hours while you keep a diary of activities and symptoms. It is painless; the patches can occasionally irritate the skin. | MedlinePlus Holter MedlinePlus AFib |
| Patch monitor | An adhesive patch on the chest, with no wires, records continuously, for 14 days in MedlinePlus's event monitor article and 1 to 2 weeks in its AFib article. | MedlinePlus event monitors MedlinePlus AFib |
| Event monitor | A device you carry or wear for up to 30 days that saves your heart rhythm when you feel symptoms, and in some models starts on its own if it detects an abnormal rhythm. | MedlinePlus event monitors |
| Implanted loop recorder | A small monitor placed under the skin of the chest, with a small cut under local numbing, that can record heart rhythm for 3 or more years. | MedlinePlus event monitors |
| Smartwatch or phone ECG | A consumer device uses ECG technology to record your heart rhythm. FDA rules describe this device type as giving information for identifying heart rhythm problems and say it is not intended to provide a diagnosis. | 21 CFR 870.2345 USPSTF, 2022 |
| Irregular rhythm notification | A watch or phone uses light sensors (photoplethysmography) to read the pulse and flags an irregular rhythm. FDA rules describe this device type the same way: information for identifying irregular rhythms, not a diagnosis. | 21 CFR 870.2790 ACC/AHA, 2023 |
The routine 12-lead ECG and why it is not advised for everyone: ECG at a checkup.
What a smartwatch or phone alert does and does not mean
- It is not a diagnosis. FDA rules classify both over-the-counter ECG software and light-sensor rhythm software as giving information for identifying heart rhythm problems, and say neither is intended to provide a diagnosis. (21 CFR 870.2345) (21 CFR 870.2790)
- Light-sensor alerts can prompt an ECG. The 2023 ACC/AHA guideline says photoplethysmography may alert people to get an ECG tracing, but is not reliable enough to establish AFib. (ACC/AHA, 2023)
- A clinician confirms it. The same guideline recommends that a first AFib diagnosis be made by a clinician looking at the ECG signals, whatever device recorded them, because automated algorithms vary in accuracy. (ACC/AHA, 2023) NICE uses a 12-lead ECG to confirm AFib, to avoid relying on less accurate devices such as mobile and lead-I ECG devices. (NICE NG196)
- Read the device labeling. FDA rules require the labeling to state the situations in which the device may not work as expected, what it measures and shows, and guidance on what results mean, and require testing that users understand when to seek medical care. (21 CFR 870.2345) (21 CFR 870.2790)
- No alert is not a guarantee. Some people with AFib have no symptoms and do not know they have it, and episodes can come and go. (MedlinePlus AFib topic) (MedlinePlus AFib)
- Mass screening finds little. The ACC/AHA guideline notes that population screening with a smartwatch app only rarely found new AFib. (ACC/AHA, 2023)
What happens after a positive screen
In general terms: a provider diagnoses AFib from your medical and family history, a physical exam and an ECG, and possibly other tests. (NHLBI AFib diagnosis) If the rhythm comes and goes, you may wear a monitor for a while. (MedlinePlus AFib) Blood tests, such as potassium and thyroid hormone, and an echocardiogram (heart ultrasound) can look for a cause, and the provider assesses your risk of blood clots. (NHLBI AFib diagnosis)
Your doctor decides what your result means for you. This page does not give treatment advice. If you were told a result was abnormal, see after an abnormal screening result for questions to ask.
Symptoms are different
Screening advice is for people without symptoms. MedlinePlus lists these possible symptoms of AFib: a pulse that feels rapid, racing, pounding or thumping, fluttering, irregular, or too slow; feeling your heartbeat (palpitations); confusion; dizziness or lightheadedness; fainting; fatigue; weakness; loss of ability to exercise; shortness of breath and anxiety; sweating; and chest pain or pressure, which may be a sign of a heart attack. (MedlinePlus AFib)
MedlinePlus: "Call 911 or the local emergency number right away if you have chest pain or pressure."
When to contact a medical professional: "Contact your provider if you have symptoms of AFib or flutter." (MedlinePlus AFib)
Where they differ:
- USPSTF: evidence insufficient for adults 50 and older without symptoms (I statement, 2022). (USPSTF, 2022)
- AHA and American Stroke Association: as the USPSTF summarizes them, active screening in primary care for people older than 65, by pulse check followed by an ECG as indicated, can be useful. The American Academy of Family Physicians supported the 2018 USPSTF statement on ECG screening for AFib. (USPSTF, 2022)
- ACC/AHA (2023): benefit of screening people at high predicted risk is not yet established. (ACC/AHA, 2023)
- UK: the UK NSC does not recommend a national screening program, because it is unclear whether all types of AFib carry the same stroke risk, how well treatment works in people found by screening, and whether screening beats current detection; it plans to review again after the SAFER trial. (UK NSC) NICE advises a pulse check when AFib is suspected, for example with breathlessness, palpitations, fainting or dizziness, chest discomfort, or a stroke or TIA, then a 12-lead ECG if the pulse is irregular. (NICE NG196)
Questions people ask
Should adults over 50 without symptoms be screened for AFib?
The USPSTF found the evidence insufficient to weigh the benefits and harms of screening adults 50 and older who have no signs or symptoms (I statement, 2022), so clinicians use their judgement about whether and how to screen. Feeling the pulse is already part of routine care. (USPSTF, 2022)
My watch said my rhythm was irregular. Do I have AFib?
Not necessarily. FDA rules say these devices are not intended to provide a diagnosis, and the 2023 ACC/AHA guideline says light-sensor (photoplethysmography) alerts are not reliable enough to establish AFib; they may prompt an ECG, and a first AFib diagnosis is made by a clinician looking at the ECG tracing. Tell your provider about the alert. (21 CFR 870.2790) (ACC/AHA, 2023)
If my watch never alerts, does that mean I do not have AFib?
No. FDA rules require these devices to list situations in which they may not work as expected, some people with AFib have no symptoms, and AFib can come and go, which is why longer monitors are sometimes used. (21 CFR 870.2790) (MedlinePlus AFib) (MedlinePlus AFib topic)
What is subclinical AFib?
AFib picked up by an implanted or wearable device in someone without symptoms and without earlier ECGs showing it. The USPSTF says the stroke risk of short, device-detected episodes is less well understood than for AFib found in the clinic. (ACC/AHA, 2023) (USPSTF, 2022)
Who is more likely to get AFib?
MedlinePlus lists getting older, especially over 65, family history, heavy alcohol use, smoking and some drugs, and conditions such as high blood pressure, diabetes, heart failure, heart valve disease, obesity, an overactive thyroid, chronic kidney disease, lung disease and sleep apnea. (MedlinePlus AFib topic)
Does the UK screen for AFib?
No national program. The UK NSC does not recommend one, after its 2019 review, and will look at the evidence again after the SAFER trial. NICE advises a pulse check when AFib is suspected and a 12-lead ECG to confirm it. (UK NSC) (NICE NG196)