Apps can detect atrial fibrillation, but benefits and harms are uncertain

- Kenny Lin, MD, MPH

The March 15 issue of AFP included a recommendation statement from the U.S. Preventive Services Task Force (USPSTF) and Putting Prevention Into Practice case study on screening for atrial fibrillation with electrocardiography (ECG). The USPSTF concluded that current evidence is insufficient to assess the balance of benefits and harms of testing for atrial fibrillation in primary care patients without suggestive symptoms. In an accompanying editorial, Drs. John Mandrola and Andrew Foy discussed several potential downsides of ECG screening for atrial fibrillation: low prevalence, a high number needed to screen to prevent one stroke, high costs, false positive results, and uncertainty about the effects of anticoagulants in persons with subclinical atrial fibrillation.

At the American College of Cardiology meeting last week, Dr. Mandrola interviewed Dr. Mintu Turakhia, a co-principal investigator of the Apple Heart Study, regarding initial findings reported at the conference. More than 400,000 U.S. adults with Apple Watches installed an app that used an algorithm to analyze heart rate variability and notified users if five out of six samples over a 48-hour period suggested an irregular heart rate. Of the 2100 individuals (~0.5%) who received these notifications, the positive predictive value for ECG-confirmed atrial fibrillation was 84%. The app's sensitivity and false negative rate are unknown because users who did not receive notifications did not have ECG monitoring. Also, the study was not designed to evaluate health outcomes.

A planned pragmatic randomized trial will enroll adults age 65 years and older to determine if screening for atrial fibrillation and other heart rhythm abnormalities using the Apple Watch app leads to reduced stroke rates and/or improved cardiovascular health. In the meantime, family physicians will likely start seeing more patients for evaluation of possible cardiac rhythm abnormalities detected by wearable devices. A recent JAMA article reviewed the limitations of such devices at detecting atrial fibrillation, tachycardia, and bradycardia and offered a suggested approach to evaluation and management.