Six-Lead ECG Device Highly Accurate for Atrial Fibrillation Detection

A study was conducted to compare 3 ECG-based devices to determine how accurately they detect atrial fibrillation.

The Kardia Mobile 6-lead electrocardiogram (ECG) device is superior for detecting atrial fibrillation (AF) when compared with a pair of single-lead smartwatches according to cardiologists’ interpretation. These findings were published in the American Heart Journal.

A prospective, nonrandomized study compared ECG-based devices for AF detection at a nonacademic, regional hospital in Blaricum, the Netherlands. The study cohort included adult patients admitted for electrical cardioversion for AF or atrial flutter (AFL) from February 2020 to March 2021.

Standard 12-lead ECGs were recorded in the supine position. This was followed by consecutive, supervised 30-second ECGs by different devices before and after the electrical cardioversion.

The participants were randomly allocated 1:1 to have a single-lead II ECG with the Withings Move ECG (Withings) or Apple watch series 5 (Apple Inc). The Withings or Apple watch was placed on the left knee and held with the right hand. The Kardia Mobile 6-lead (AliveCor) was placed on the left knee with both thumbs on the device to simultaneously record a 6-lead ECG.

A total of 220 patients were included in the study (aged 70±10 years, 35% women), and 415 12-lead ECGs were recorded (45% sinus rhythm [SR], 45% AF, 10% AFL). Repeat ECGs were not available in 25 patients.

In the 3 devices studied, there were the following comparable proportions of uninterpretable ECGs (P >.05 for all comparisons in percentage uninterpretable):

  • The Withings lead I: 20% (12% inconclusive, 4% high heart rate, 2% low heart rate, 1% unclassified)
  • The Apple lead I: 20% (11% inconclusive, 6% high heart rate, 3% low heart rate)
  • The Kardia 6-lead: 24% (15% inconclusive, 3% high heart rate, 1% low heart rate, 4% unclassified)

The sensitivity and specificity of the AF detection algorithms were 91% to 99% when excluding uninterpretable ECGs, which were similar for all devices (P >.05 for all head-to-head comparisons in accuracy).

The cardiologists’ interpretation of the Withings leads I and Apple lead I had a sensitivity and specificity of 94% to 96%. The Kardia 6-lead had significantly better accuracy (sensitivity 99% and specificity 97%; correct classifications 97.9%; 95% CI, 96.8%-99.0%; P =.013 vs Withings, P =.024 vs Apple).

An average of the 2 cardiologists’ interpretations revealed a correct AFL diagnosis in 28% of cases for the Withings lead I and 33% for the Apple lead I. The Kardia 6-lead device was the most accurate in differentiating among SR, AF, and AFL, with a correct diagnosis of AFL in 63% of all cases (P <.001 compared with Withings and Apple).

Study limitations include that it has a single-center design with patients with AF who were scheduled for electrical cardioversion in a regional hospital with a uniform protocol and high inclusion rate. Also, the study does not evaluate devices used by patients themselves at home, and false classifications may be more prevalent in patients with symptomatic premature atrial contractions or other types of supraventricular tachycardias.

“Our findings suggest Kardia 6L [6-lead] has clinical benefit compared to the single-lead devices, but only when reviewed by cardiologists,” the researchers wrote. “In comparison to single-lead ECGs, a 6-lead device can more accurately diagnose AF and may lead to less health care utilization when uncertainty remains after cardiologists’ interpretation.”


Scholten J, Jansen WPJ, Horsthuis T, et al. Six-lead device superior to single-lead smartwatch ECG in atrial fibrillation detection. Am Heart J. Published online July 16, 2022. doi: 10.1016/j.ahj.2022.06.010