The use of devices like Apple watches may offer a more affordable and less burdensome modality to diagnose atrial fibrillation.
By the year 2030, it is estimated that 12.1 million people in the US will be diagnosed with atrial fibrillation (AF).1,2 AF is the most common sustained arrhythmia with more than 5.6 million Americans currently diagnosed. In 2015, an estimated 591,000 cases of undiagnosed AF were reported; however, discovering the exact prevalence of undiagnosed AF can be challenging.
With the prevalence of AF continuing to increase, the importance of early detection will be imperative for preventing the onset of stroke and heart failure.3 A 12-lead electrocardiogram (ECG) is the current gold standard for the diagnosis and management of AF; however, patients may experience barriers to care such as cost, scheduling, and transportation. The use of a wearable wrist monitoring device may be an alternative, less burdensome modality to diagnose AF.
Smartphone and a smart watch | Image credit: Halfpoint | stock.adobe.com
One in 3 Americans utilize a wearable device to track health and fitness data.4 As new advances in technology arise, companies producing these devices continue to test the limits. Each new model brings a new design, updated software, and capabilities that were never thought possible. Many wearable devices are equipped with the technology to measure heart rate and rhythm by utilizing ECG or photoplethysmography (PPG). ECG is still considered the gold standard for heart rate and rhythm measurement; however, PPG is increasingly gaining more evidence and popularity. Traditionally, ECG refers to a 12-lead ECG; however, other portable devices, such as a Holter monitor, are able to record electrical activity of the heart.
More recently, smartwatches have developed the capability of recording an ECG. Although chest-strap monitors and ECG patches may provide a more reliable measurement of the heart’s electrical activity, smartwatches may prove to be a more convenient method. As smartwatches are only able to record a single-lead ECG, they may not be preferred in the diagnosis of more complex conditions but can still be useful to diagnose simple and common arrhythmias such as AF.5
Although not as accurate as ECG, PPG can also be used to measure heart rate and detect certain arrhythmias, especially when used with single-lead ECG. PPG is a simple and low-cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue.5 Even in combination with single-lead ECG, PPG has limitations. The PPG sensor must be in direct contact with the skin, which can be difficult to achieve. Skin moisture, color, and the presence of tattoos may also affect PPG accuracy.6
The Apple Heart Study was conducted to determine the ability of a PPG capable smartwatch and a connected application to identify AF. Researchers recruited 419,297 participants without a known history of AF from the US. Participants wore a PPG-enabled Apple Watch and were monitored using an Apple iPhone app that notified participants of an irregular pulse. If AF was detected, a telemedicine visit was initiated, and an ECG patch was mailed to the participant to be worn for up to 7 days. The objectives of the study were to estimate the proportion of notified participants with AF shown on an ECG patch and the positive predictive value of irregular pulse intervals.7
Irregular pulse notifications were received by 2161 participants (0.52%). The probability of receiving an irregular pulse notification was low. Among participants who received a notification of an irregular pulse, 34% had AF on subsequent ECG patch readings and 84% of notifications were concordant with AF. It is important to note that patients who were alerted of irregular pulses but subsequently had no findings of AF on the ECG may have also had paroxysmal AF. Overall, this study showed that although the Apple Watch was not entirely accurate, it played a part in alerting patients to actively seek medical attention for further evaluation.7
The Apple Heart study took place from November 2017 to August 2018. At that time, the most current series of the Apple Watch was the Apple Watch 3, which only had PPG capabilities. The HEARTLINE trial is a current ongoing trial investigating the Apple Watch 4 or newer models, which have combined PPG and ECG capabilities. This study is the first randomized trial investigating whether detecting symptomatic and asymptomatic AF with the use of an Apple Watch 4 or a newer model is achievable. The trial aims to evaluate whether AF detection with a wearable device would improve clinical AF diagnosis, reduce cardiovascular outcomes, and increase compliance with anticoagulation therapy.8
More recently, the company Withings conducted a prospective nonrandomized open-label comparative multicenter study to evaluate the diagnostic performance of their product, ScanWatch. The study had 262 participants and took place between December 2019 and April 2021 in Paris, France. The ScanWatch is a smartwatch that possesses 30-second single-lead ECG technology. Data from the watch were uploaded to an app and classified as AF, normal sinus rhythm, noise, or other by a designated algorithm. The ScanWatch ECG readings were simultaneously taken with a reading from a 12-lead reference ECG and independently compared by 3 blinded, board-certified cardiologists.9
The results of this study showed that the sensitivity for AF detection when considering all 4 diagnostic categories was 0.77 (95% CI lower bound 0.675), and the specificity was 0.924 (95% CI lower bound 0.912). In contrast, the Apple Watch sensitivity for AF detection was 0.852 and the specificity was 0.905.9 In other words, 33% of patients with AF were not identified as having AF by the ScanWatch and 7.6% of patients who were identified as having AF did not have AF. The Apple Watch has greater sensitivity as only 14.8% of patients with AF were not identified as having AF.8,9
Rachel Barker, PharmD, is a PGY-2 ambulatory care pharmacy resident at AdventHealth Celebration.
Raechel Lozano, PharmD, BCACP, is a clinical pharmacist and PGY-2 ambulatory care pharmacy residency program director at AdventHealth Celebration.
Kimberly Finley, PharmD, BCACP, is clinical pharmacy manager and PGY-1 ambulatory care pharmacy residency program director at AdventHealth Celebration.
Hypertension accounts for approximately 1 in 5 cases of AF and is a leading cause of morbidity and mortality.6,10 Utilizing a wearable device for accurate home blood pressure monitoring has the potential to improve screening and management of hypertension and, therefore, reduce the risk of developing AF. The Omron HeartGuide is the first clinically accurate, wearable blood pressure monitor designed in the form of a wristwatch. The HeartGuide was utilized in the first study comparing a wearable watch-type blood pressure monitor with a conventional ambulatory blood pressure monitoring (ABPM) device in both in-office and out-of-office settings. A total of 50 participants were included, and at least 4 blood pressure readings were taken throughout the day, 10 minutes apart. Although the study had a small patient population, the results were promising. The mean difference (±SD) in systolic blood pressures (average of 2 readings) between the HeartGuide and ABPM device was 0.8 ± 12.8 mmHg (p = 0.564) in the office and 3.2 ± 17.0 mmHg (p < .001) outside of the office.11 Authors concluded that the difference between the 2 devices was acceptable both in and out of the office. Further studies are likely warranted prior to recommending devices like the HeartGuide for the screening and management of hypertension.
Currently, there are no regulatory oversight policies governing commercial wearable devices; however, the FDA may provide approval if a 501(k) premarket submission is made and demonstrates that the device to be marketed is as safe and effective as a legally marketed device. A 510(k) must provide a comparison between the device to be marketed and one or more similarlegally marketed devices to support the substantial equivalence claim.6 No wearable wrist devices for monitoring or identifying AF or any other medical conditions have been granted FDA approval, only FDA clearance (Table 1). Based on the results of the HEARTLINE trial, there is a possibility that the Apple Watch series 4 and higher may receive FDA approval.
As technology is ever evolving, advances are being made in improving the capabilities of wearable monitoring devices. Further clinical trials are required to demonstrate that wearable monitoring devices are as capable as the current standard of care in medical device monitoring. Although devices with technology like the Apple Watch may not have previously been able to accurately diagnose AF, there is hope that in the future newer technology will be able to diagnose AF more accurately or, at the very least, continue to notify patients of potential arrhythmias and lead them to seek medical care.
