Apple Watch's abnormal pulse feature driving many unnecessary healthcare visits, Mayo Clinic researchers say

It takes roughly seven patients presenting after an abnormal pulse alert to establish one clinically actionable cardiovascular diagnosis, according to the researchers' chart review.
By Dave Muoio
02:34 pm

A new review of Apple Watch-related presentations suggests that the device's abnormal pulse detection feature may be fueling unnecessary healthcare utilization.

"The observation that new clinically actionable cardiovascular diagnoses of interest were diagnosed in only 11.4% of patients following medical evaluation as directed by the treating provider suggests a high false positive rate as a screening tool for undiagnosed cardiovascular disease," Mayo Clinic researchers wrote in the Journal of the American Medical Informatics Association. "False positive screening results have the potential to lead to excessive healthcare resource utilization and anxiety among the 'worried well.'”

The retrospective look at clinical documentations also suggests that a sizable portion of those presenting used the Apple Watch's feature "in a manner inconsistent with FDA guidance." The abnormal pulse detection feature is accessible across all generations of Apple Watch devices, and is not to be confused with the ECG atrial fibrillation tool introduced with the Series 4 Apple Watch.

The researchers reported no relevant conflicts of interest, but noted that their employer does have a partnership with competing consumer ECG vendor AliveCor. Both the Mayo Clinic and AliveCor did not have a role in the study, they wrote.


Among 264 patients whose clinical documentation was included in the study, 15.5% had records explicitly noting an abnormal pulse alert generated by the feature. The remainder included reference to the watch and detection of abnormal pulse but did not explicitly mention that the user had received a generated alert, which the researchers noted could be a result of either incomplete documentation or the patient's manual use of the Apple Watch's heart monitoring application.

Patients who experienced symptoms were more likely to undergo diagnostic testing as part of their evaluation (78.5% versus 60.9%; p = .004). There was no significant difference in the proportion of patients with or without a documented abnormal pulse alert from the watch who underwent diagnostic testing.

Overall, 11.4% of patients received clinically actionable diagnoses. This diagnosis rate rose slightly to 15% among those documented to have received the 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 [one] diagnosis of clinically actionable cardiovascular disease," the researchers wrote. "Among the 15 asymptomatic patients who presented following an abnormal pulse alert, only one was diagnosed with a clinically actionable cardiovascular diagnosis, yielding a number needed to diagnose of 15 (95% confidence interval, 2.9-286.5)."

Also of note were the patient populations included in the analysis. Twenty-two percent had pre-existing atrial fibrillation and 8.7% were younger than 22 years – both of which would exclude these patients from the FDA's guidance for this feature.

"Stricter access controls are encouraged to ensure real-world use conforms with FDA guidance," the researchers wrote.


The researchers queried clinical notes from all Mayo Clinic sites between December 6, 2018 and April 2, 2019 for those including the term "Apple Watch" (n = 598). After excluding 64 who declined the use of their records for research, the researchers manually reviewed the remaining records to cut out another 270 that did not suggest use of the smartwatch's abnormal pulse detection capabilities.

Among the remaining 264 patients, the researchers extracted data on the patients' demographics, clinical characteristics, performed evaluations and eventual diagnoses. Diagnoses of atrial fibrillation, atrial flutter, atrioventricular block, supraventricular tachycardia, ventricular fibrillation and ventricular tachycardia were all considered to be "clinically actionable cardiovascular diagnoses of interest" for the purpose of the study.


The irregular rhythm detection feature received FDA De Novo clearance and launched alongside Apple's ECG functionality in late December 2018. At the time, the company highlighted data suggesting strong agreement between simultaneous use of the irregular notification feature and a worn ECG patch. Still, the FDA and others noted that unnecessary healthcare visits could be a risk of the new feature, and that real-world data does not always paint the same picture as a trial.

The years since have seen more and more health sensors and features land on the consumer smartwatch. As of earlier this month, this includes blood oxygenation and VO2 Max values.


"The FDA and Apple must carefully consider the unintended consequences of widespread direct-to-consumer screening for asymptomatic atrial fibrillation, including overutilization of healthcare resources owing to false positive screening results and use of screening tools by users in whom they have not been adequately studied," the researchers wrote.


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