Victorian cardiologists evaluate smartwatch ECG function

The case for wearable technology like smart watches being used to screen for AF has been bolstered with new Australian research showing that a recent FDA-approved device accurately picked up the abnormal rhythm in 94% of patients who simultaneously had 12-lead ECGs.

Key findings from the study were presented at the European Society of Cardiology scientific meeting in Paris.

Speaking to the limbic ahead of the meeting, study lead Dr Andrew Teh, cardiologist at Box Hill Hospital in Melbourne, said the findings will help doctors gain an understanding of how trustworthy the single-lead ECG readings from such devices are.

“As cardiologists many of us have had had patients present with readings from their watches and we haven’t really known if we could trust those readings so these kinds of validation studies are really critical so that we, and our patients, have that information.”

Dr Teh and colleagues recruited 200 hospital patients for the multicentre validation study and recorded a 30-second smartwatch ECG tracing alongside a simultaneously recorded 12-lead ECG, which was reviewed by a cardiologist.

The FDA gave the green light for the specialised wristband used in the study, Kardiaband, to be marketed as a heart-monitoring wristband for the Apple Watch early last year.

The wristband, when paired with the Apple Watch, can record a 30 second single lead ECG when the wearer places a finger from the opposite hand onto a metal sensor attached to the band, which it then interprets as sinus rhythm, AF or unclassified.

In the current study, Dr Teh said the device identified 38 patients to be in AF, including two new diagnoses, and 162 patients in sinus rhythm.

“Of the patients who had AF, the watch picked up 94% of those accurately and when it reported that the rhythm was normal it was very accurate as well with only 1.6% of those patients actually having AF.”

But he said one limitation of the technology at the moment remains that the watch could not classify a proportion of tracings – around 20%.

According to Dr Teh, sensitivity for AF and sinus rhythm using the wristband was 89.5% and 92.9% respectively. This improved to 94.4% and 98.3% when excluding unclassified readings, which were reviewed by two electrophysiologists (EP) who were blinded to the 12-lead ECG readings.

Their review revealed comparable testing parameters to the smartwatch diagnoses with an overall sensitivity of 87.8% (EP1: 3 false positives, 1 false negative) and 90.2% (EP2: 2 false positives, 1 false negative).

Dr Teh said while wearable devices are shaping up as a cost-effective screening tool for AF, the technology still has a way to go in terms of accurately monitoring heart rate when a person is in AF.

In a separate study, Dr Teh found the device significantly underestimated heart rate while patients were in AF.

“We found a difference of almost 20-25 beats a minute when patients were in AF with the watch giving a much lower value than a 12-lead ECG and that’s probably because pulse strength for instance is variable when you’re in this irregular rhythm – it’s not as strong so the reading of the pulse rate is not as accurate.”

“What’s great about these devices is they can be directly purchased by the consumer and so in this workflow the patient can get their own data themselves and then present to the doctor for interpretation or management of the data; it’s quite a different paradigm to current healthcare practices … can you trust the devices enough to be able to act on the diagnosis that it provides? I’m not sure if we’re quite there yet.”

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