Advantages and limitations of mobile monitoring for cardiac arrhythmias

During the first wave of the pandemic, when hydroxychloroquine was still thought to be an effective treatment for hospitalized patients with COVID-19 (subsequent studies have shown otherwise), some U.S. hospitals used personal electrocardiogram (ECG) devices to monitor these patients for drug-induced QT interval prolongation to conserve personal protective equipment and telemetry monitors. Such devices were already being used by patients with known cardiac conditions to monitor their heart rhythms in out-of-office settings.

As I discussed in a previous AFP Community Blog post, wearable devices such as the Apple Watch are also being studied to detect atrial fibrillation in asymptomatic primary care patients. In a 2019 study of more than 400,000 U.S. Apple Watch wearers with no self-reported history of atrial fibrillation, about 1 in 200 individuals received an irregular pulse notification and were scheduled for a telemedicine visit with a clinician to confirm study eligibility and triage those with urgent symptoms to the emergency department. Participants without urgent symptoms were mailed an ECG patch to wear for up to 7 days and then mail back to the study center.

Of the 450 participants who returned an ECG patch, 34% were confirmed to have atrial fibrillation, with a higher diagnostic yield in persons age 65 years or older. Of the 86 patients whose watches generated irregular pulse notifications when they were wearing the ECG patch, the positive predictive value for atrial fibrillation was 84%. In a survey completed at 90 days by patients who received an irregular pulse notification, 28% reported being prescribed a new medication, 33% were referred to a specialist, and 36% were recommended to have additional testing.

In the November 1 issue of American Family Physician, Dr. Madhavi Singh and colleagues reviewed the diagnostic test features of KardiaMobile, a $99 single-lead device that connects wirelessly to a smartphone app to generate an ECG tracing with automated interpretation. In studies of patients with known or suspected arrhythmias, KardiaMobile had greater than 90% sensitivity and specificity for atrial fibrillation or atrial flutter compared to a standard 12-lead ECG. However, no studies have compared its accuracy with a Holter or event monitor, and effects on patient outcomes are uncertain, particularly in populations at low risk for arrhythmias. (In 2018, the U.S. Preventive Services Task Force found insufficient evidence to assess the balance of benefits and harms of screening for atrial fibrillation, which has several potential downsides.) The authors concluded that similar to the Apple Watch, "further studies are needed before KardiaMobile can be recommended for use in seemingly healthy patients."