Wearable Tech and Atrial Fibrillation: A New Frontier in Heart Monitoring

Three recent clinical trials have investigated the use of consumer wearable devices—including smartwatches and smartphone apps—for detecting and managing atrial fibrillation (AF). Published across multiple medical journals, the studies evaluated different technologies and patient populations, producing varied results regarding diagnostic accuracy, clinical utility, and operational feasibility.

Smartphone Monitoring for Cardioversion Cancellation

A study published in JAMA Cardiology tested a smartphone-based heart rhythm monitoring system to reduce same-day cancellations for electrical cardioversion in AF patients. The trial was conducted at Danderyd Hospital in Stockholm, Sweden, between 2022 and 2025.

Participants and Method

206 patients were randomized to active monitoring or standard care. Active monitoring used a smartphone app (CORAI) based on photoplethysmography (PPG) to detect normal heart rhythm early.

Key Results

The same-day cancellation rate was 4.8% in the monitored group compared to 23.2% in the control group.

Cancellations due to spontaneous return to normal rhythm occurred in 1.0% of the intervention group versus 18.2% in the control group, representing a 94.7% relative risk reduction.

In the control group, only 3 patients proactively contacted healthcare providers about cancelling their procedure, despite many having normal rhythm confirmed on later recordings.

Researcher Statements

Jonatan Fernstad, researcher and founder of Corai Medicinteknik AB, stated the method could help avoid unnecessary visits. Johan Engdahl, professor at Karolinska Institutet, noted that 99% of participants owned a smartphone (median age 70), suggesting broad potential for access. He added that future research will study detection of unknown atrial fibrillation.

Funding and Disclosures

The study was funded by Vinnova and the Swedish Heart-Lung Foundation. Jonatan Fernstad has a financial interest in Corai Medicinteknik AB. Other authors reported receiving fees or grants from pharmaceutical and medtech companies.

Smartwatch Monitoring in High-Risk Older Adults (EQUAL Trial)

The randomized EQUAL trial, conducted by researchers at Amsterdam UMC and published in the Journal of the American College of Cardiology (JACC), examined the use of Apple Watches for AF detection in patients aged 65 and older with elevated stroke risk.

Participants and Method

437 patients (mean age 75 years) with a CHA₂DS₂-VASc score of at least 2 for men and 3 for women were enrolled across two secondary care centers in the Netherlands. 219 participants were assigned to wear an Apple Watch (Series 5 or 8) for at least 12 hours daily while awake, while 218 received standard care. Smartwatch users were prompted to record a 30-second ECG upon symptoms or irregular pulse notifications, with recordings transmitted to a telemonitoring app.

Key Results

After six months, AF was detected in 21 patients in the smartwatch group (9.6%) compared to 5 patients in the standard care group (2.3%), representing a hazard ratio of 4.40.

Of the smartwatch-detected cases, 57% were asymptomatic, while all cases in the control group were symptomatic.

The absolute increase in AF detection was 7.3%, with a number needed to screen of 14.

Diagnostic Accuracy

Of 37 patients with an initial smartwatch ECG labeled as AF, 20 were diagnosed with clinical AF, yielding a positive predictive value of 54%. All patients diagnosed with AF initiated oral anticoagulation.

Additional Observations

The study observed a numerically, but not statistically significantly, lower rate of emergency department visits in the smartwatch arm (5.9% vs 8.3%). The trial was not powered to detect differences in clinical outcomes.

Researcher Statements

Michiel Winter, cardiologist at Amsterdam UMC, stated that the results provide evidence that wearables are suitable for long-term screening and increase the detection rate of heart arrhythmias. He noted that the most important achievement was demonstrating the feasibility of population-based screening using smartwatches in a high-risk AF population.

Nicole van Steijn, PhD candidate at Amsterdam UMC, noted that while wearables combining PPG and ECG functions have existed, their effectiveness in real-world screening had not been previously investigated.

Future Research

Investigators noted that embedding consumer wearables into telemonitoring workflows offers a scalable model for integrating digital screening into routine cardiology practice. The clinical impact of treating screen-detected or subclinical AF requires further confirmation from ongoing outcome trials such as REGAL, SAFER, and Heartline.

Smartphone App and Bed Sensor System (CARE-DETECT Trial)

The CARE-DETECT trial, published in Scientific Reports, investigated the combination of a smartphone app with a bed-based heart rhythm sensor for detecting irregular heartbeat rhythms in high-risk cardiac patients following invasive procedures.

Participants and Method

This investigator-initiated, prospective, randomized, open-label, single-center study was conducted in Finland. It enrolled 150 patients hospitalized for coronary artery disease or valvular heart disease who were undergoing invasive cardiac procedures. All participants had high risk for AF and strokes (CHA2DS2-VASc score ≥4 or ≥2 with enrichment criteria). Recruitment was halted at 150 patients after an interim analysis indicated a high number of device alerts not resulting in confirmed AF diagnoses.

The intervention group (n=78) used a bed sensor (EMFIT QS) for overnight ballistocardiogram monitoring and performed twice-daily smartphone recordings using the CardioSignal app for three months post-discharge. The control group (n=72) received usual care.

Key Results

New AF within three months was detected in 6 of 78 patients (7.7%) in the intervention group, compared to zero of 72 control patients (absolute risk difference 7.7%, p=0.029). Five of these six AF episodes occurred after discharge, with a median time to diagnosis of 34 days.

False Alarm Rate

Among intervention patients completing follow-up, 33 of 68 (48.5%) experienced device alarms that did not lead to ECG-confirmed AF.

A total of 47 long-term ECG Holter recordings were triggered, equating to 7.8 Holters per true AF diagnosis. Most alerts were attributed to sinus arrhythmia or supraventricular or ventricular ectopic beats rather than AF. The patient-level positive predictive value among those with at least one alert was 15.4%.

Implications

While the intervention improved AF detection, investigators noted that some differences might reflect greater surveillance rather than a true incidence difference, given the absence of continuous rhythm monitoring in the control group. The study was not powered to assess stroke outcomes or the net clinical benefit of anticoagulation. High exclusion and withdrawal rates in the intervention arm, partly due to device burden, raised questions about scalability.

Conclusions

The trial indicated that patients at high stroke risk following cardiac procedures may be a suitable population for targeted AF screening. However, with a positive predictive value of 15.4%, the current multi-device strategy was not considered suitable for routine clinical implementation. Future research is needed to reduce false alerts, clarify the AF burden threshold for treatment, and evaluate overall cost-effectiveness.

Summary of Findings Across Studies

The three trials demonstrate that consumer wearable devices can increase detection of atrial fibrillation in various clinical contexts.