Cleveland Clinic Studies Accuracy of Apple Watch 4 for Atrial Fibrillation Detection

Watch display only picked up 41% of AFib occurrences in hospitalized patients, additional waveform PDF detected 98% of occurrences

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Cleveland Clinic researchers have found that the Apple Watch 4 (AW4) identified only 41% of atrial fibrillation (AFib) instances when viewing the watch display alone. In addition to the watch display, the AW4 provides a downloadable PDF to detect AFib, which detected AFib – a type of irregular heartbeat – 98% of the time.

Marc Gillinov, M.D.

In the study, researchers compared both types of readings to a telemetry electrocardiogram (EKG or ECG), which is a test that continuously measures the electrical activity of the heartbeat while the patient is the hospital.

“A standard ECG remains the gold standard for detecting Afib,” said Marc Gillinov, M.D., Cleveland Clinic chair of thoracic and cardiovascular surgery and the Judith Dion Pyle Chair in Heart Valve Research. “At this point, consumer wearables and watches don’t have the accuracy to replace the ECG. A diagnosis of Afib requires input from a physician.”

The study was published today in Circulation.

The study looked at 50 postoperative cardiac surgery patients at Cleveland Clinic on telemetry ECG monitoring. Heart rhythm assessments were obtained three times a day (morning, early/late afternoon, and early/late evening) over two days, resulting in six assessments per patient. Of the possible 300 rhythm assessments, researchers obtained 292 readings. Two patients were discharged before the completion of the study. The researchers chose to study cardiac surgery patients because these patients frequently develop Afib while in the hospital. Afib is a common after cardiac surgery.

Milind Desai, M.D.

“The data suggests that further technological advances are necessary before these wearables can be fully incorporated into current clinical management,” says Milind Desai, M.D., Cleveland Clinic cardiologist and director of clinical operations and Haslam Family Endowed Chair in cardiovascular medicine.

During each reading, patients were provided an Apple Watch 4 at random and provided with instructions on how to activate the heart rhythm reading on the app. At the same time, an automatically-generated PDF of the waveform on the Apple Health App was exported and a rhythm strip were saved.  The ECGs were generated and viewed by a cardiologist according the instructions provided by Apple.

Half of the patients had more than one AFib occurrence during their hospital stay. The telemetry ECG picked up all 90 AFib instances.

The results:

  • AW4 app display only
    • Correctly identified 34 of the 90 (41%) instances of atrial fibrillation
    • In the 25 patients who had more than one instance of AFib, AFib was identified in 19
    • In patients whose hearts were in sinus, or normal rhythm, there were no notifications of afib, indicating there were no false positives
  • AW4 with a retrievable PDF of the waveform strips
    • 284 rhythm assessments were gathered
    • In eight instances a reading failed to generate, this was counted as incorrect rhythm interpretations
    • Correctly identified 84 of the 90 (96%) instances of atrial fibrillation
    • In the 25 patients who had more than one instance of AFib, AFib was shown in 24
    • In patients whose hearts were in sinus, or normal rhythm , zero instances of Afib were picked up, indicating there were no false positives

According to the American Heart Association, about 2.7 million Americans are living with AFib.   Atrial fibrillation (AF or AFib) is the most common irregular heart rhythm that starts in the atria. Some people live for years with atrial fibrillation without problems. Atrial fibrillation is associated with an increased risk of stroke, heart failure and even death.

About Cleveland Clinic

Cleveland Clinic is a nonprofit multispecialty academic medical center that integrates clinical and hospital care with research and education. Located in Cleveland, Ohio, it was founded in 1921 by four renowned physicians with a vision of providing outstanding patient care based upon the principles of cooperation, compassion and innovation. Cleveland Clinic has pioneered many medical breakthroughs, including coronary artery bypass surgery and the first face transplant in the United States. U.S. News & World Report consistently names Cleveland Clinic as one of the nation’s best hospitals in its annual “America’s Best Hospitals” survey. Among Cleveland Clinic’s 67,554 employees worldwide are more than 4,520 salaried physicians and researchers, and 17,000 registered nurses and advanced practice providers, representing 140 medical specialties and subspecialties. Cleveland Clinic is a 6,026-bed health system that includes a 165-acre main campus near downtown Cleveland, 18 hospitals, more than 220 outpatient facilities, and locations in southeast Florida; Las Vegas, Nevada; Toronto, Canada; Abu Dhabi, UAE; and London, England. In 2019, there were 9.8 million total outpatient visits, 309,000 hospital admissions and observations, and 255,000 surgical cases throughout Cleveland Clinic’s health system. Patients came for treatment from every state and 185 countries. Visit us at clevelandclinic.org. Follow us at twitter.com/CCforMedia and twitter.com/ClevelandClinic. News and resources available at newsroom.clevelandclinic.org.

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