Clinical evaluation and diagnostic yield following evaluation of abnormal pulse detected using Apple Watch

“Apple Watch (Apple Inc, Cupertino, CA) is the most popular smartwatch on the market, with newer versions having the capability to alert users of an abnormal pulse and capture a single-lead electrocardiogram (ECG). The U.S. Food and Drug Administration (FDA) has granted clearance for the optical abnormal pulse detection and ECG features. In both clearances, false positive results leading to additional unnecessary medical procedures were identified as risks.

[..] Atrial fibrillation is the most common cardiac arrhythmia, affecting over 30 million people worldwide; however, as many as one-third of cases may be asymptomatic. Atrial fibrillation is associated with an increased risk for stroke and death. Current strategies for management of atrial fibrillation attempt to mitigate these risks; however; the optimal management of silent atrial fibrillation, including cases detected using Apple Watch, remains unclear.

[..] The Apple Heart Study aimed to prospectively assess the ability of Apple Watch to detect asymptomatic atrial fibrillation. Postenrollment study exclusion and dropout rates were high. Eighteen percent of patients who initiated a study visit because of an initial irregular pulse notification reported a preexisting diagnosis of atrial fibrillation or atrial flutter, leading to study exclusion. Abnormal pulse alerts were triggered for 2161 (0.52%) participants. Among patients with an initial alert who complied with study procedures, only 34% were diagnosed with atrial fibrillation. Among patients with a previous alert, positive predictive value of a subsequent alert for detection of atrial fibrillation by single-lead ECG was 0.84. A total of 57% of participants who were alerted of an abnormal pulse reported seeking care from a local medical provider. A total of 36% of these patients were recommended to undergo additional testing, but the specific testing performed was not reported.

[..] Clinical notes from all Mayo Clinic sites, including those in Minnesota, Arizona, Florida, Wisconsin, and Iowa, between December 6, 2018, and April 2, 2019, were queried using an internal cohort discovery tool (“Advanced Text Explorer”) to identify notes that included the term “Apple Watch.”

[..] Abnormal pulse detection using Apple Watch was noted for 264 patients who were included in the analysis. The analysis included 41 (15.5%) patients whose records explicitly noted an abnormal pulse alert (“alert”) and 223 (84.5%) patients whose records indicated abnormal pulse detection but did not explicitly mention of an alert (“no alert”). Median patient age was 55 (interquartile range, 37.75-69) years. Most patients were symptomatic at the time of abnormal pulse detection (26 [63.4%] alert patients and 151 [67.7%] no alert patients).

[..] The most common department where patients initially presented was cardiology, in which the patient had a preexisting relationship. Among patients who presented to the emergency department, 14 (33%) had received an abnormal pulse alert, only 1 of whom was asymptomatic. Approximately half of patients (n = 129, 48.9%) had a preexisting cardiovascular diagnosis, with the most common being atrial fibrillation (n = 58, 22%), followed by supraventricular tachycardia (n = 25, 9.5%) and sinus bradycardia (n = 17, 6.4%).

[..] The most commonly performed testing included 12-lead ECG (n = 158, 59.8%), Holter monitor (n = 77, 29.2%), and chest x-ray (n = 64, 24.2%). [..] Patients seen in the emergency department were more likely to undergo 12-lead ECG, chest x-ray, or bloodwork compared with patients seen in primary care or by a cardiologist (P < .001 for all).

[..] A clinically actionable cardiovascular diagnosis of interest was established in 30 (11.4%) patients (atrial fibrillation in 13 [4.9%]), including 6 of 41 (15%) patients who received an abnormal pulse alert. Therefore, for patients who experienced an abnormal pulse alert and presented for medical evaluation, 7 (95% confidence interval, 3.5-14.5) patients needed to be evaluated to establish 1 diagnosis of clinically actionable cardiovascular disease. Among the 15 asymptomatic patients who presented following an abnormal pulse alert, only 1 was diagnosed with a clinically actionable cardiovascular diagnosis, yielding a number needed to diagnose of 15 (95% confidence interval, 2.9-286.5).

[..] the true rate of clinically actionable cardiovascular diseases of interest among the study population cannot be known, as atrial fibrillation can be paroxysmal and may not be detected on follow-up evaluation, especially with short-duration follow-up. Another limitation was our lack of access to claims data to assess the actual costs of evaluation. Furthermore, a standardized approach to medical evaluation was not taken. Therefore, some patients with clinically actionable cardiovascular disease may remain undiagnosed because of incomplete evaluation by the treating provider.

[..] Regulatory trends have shifted from reliance on large-scale prospective, randomized trials to the use of observational studies capturing “real-world evidence.” The present study and the Apple Heart Study both have important limitations that constrain our ability to draw generalizable conclusions regarding the utility of the abnormal pulse detection feature of the Apple Watch. Despite these limitations, it is important to acknowledge that even false positive rates that are low in relative (ie, percentage of users) terms may translate to high absolute numbers (ie, total number of users) and yield significant healthcare overutilization.”

Full article, Wyatt KD, Poole LR, Mullan AF et al., JAMIA 2020.9.25