The function is present in the last generation of the clock. The Apple Watch Series 1,2 and 3 may also detect arrhythmias, although with less accuracy
European users of the latest version of Apple’s smart watch, the Apple Watch Series 4 , you can make an electrocardiogram – a measurement of the electrical activity of the heart – with the clock starting today if you update your iPhone and the clock to the latest version of the operating system.
The tool, one of the main novelties of the device launched in September last year , was until now limited to EE models. UU., The only territory in which Apple Watch had the necessary medical certification to perform these measurements. Now Apple has also obtained the necessary medical certification to perform it in several European countries, including Spain.
The electrocardiogram works thanks to electrodes installed in the base of the device, which makes contact with the skin, and in the crown itself.
To take a measurement, the user must select the corresponding application and touch the crown of the watch with the index finger to close the circuit. The Apple Watch will then send, for 30 seconds, a small electric current – imperceptible to the user – that will allow the elaboration of a detailed graph of cardiac activity . The option is only available to Apple Watch users who are over 22 years old.
Once the measurement is taken, the symptoms that the user feels at that moment can be added manually . These measurements are stored in the iPhone’s Health application and can be exported in PDF or mailed to the doctor. Apple has no access to them at any time .
ALSO IN THE PREVIOUS APPLE WATCH
The software update will also allow older models (except Series 0) to detect possible atrial fibrillation using the optical heart rate sensor already present in these devices. It will do so thanks to a predictive model trained by machine learning techniques and artificial intelligence.
“We believe that the ability to perform these measurements will help users to have more information about their health status when talking with their doctor,” says Dr. Sumbul Desai , vice president of the company’s health area.
These functions are not intended to replace traditional medical diagnostic tools and – this is important – can not predict or detect heart attacks , only atrial fibrillation, which is the most common type of heart arrhythmia and often happens unnoticed because it can be asymptomatic, hence the importance of being able to monitor it periodically.
An atrial fibrillation may be indicative of a future cardiac episode or a stroke but it is not necessarily a condition that requires immediate admission and in some people may occur sporadically.
Speaking to EL MUNDO, Desai explains that these tools should not be used for self-diagnosis but as a support to a conventional diagnostic process. “They are one more fact to be taken into account by a professional,” he clarifies.
Several doctors point in the same direction. “Although this type of measurement can not replace more conventional techniques, it has the potential to monitor those who have a greater predisposition to this type of problem and reduce the number of undiagnosed cases of atrial fibrillation,” says Dr. Gregory M. Marcus, director of medical research at the department of cardiology at the University of California.
As part of the clinical trials to develop these new tools, Apple carried out studies with 2,000 patients in the case of the sensor for electrocardiograms and a control group of 2,300 users and 500 patients diagnosed with atrial fibrillation for the detection algorithm of that condition .
In the first case, the tests showed a sensitivity of 98.3% of the electrocardiogram sensor when detecting atrial fibrillation and a sensitivity of 99.6% when detecting a sinusoidal heart pattern – which indicates a correct electrical activity–, compared to a twelve-point medical electrocardiogram, the typical medical diagnostic tool.
In the case of the optical sensor (less accurate), the software of the watch was able to correctly identify 80% of cases of atrial fibrillation. Of all the notifications launched, however, in 98% of the cases there was an underlying medical condition that legitimized the alert. Apple has published the results of the study on its website.
THE LARGEST STUDY ABOUT THE HEART
The function comes just after the University of Stanford has made public the results of the largest study on cardiac activity ever performed, which has had more than 400,000 participants .
The study, conducted in collaboration with Apple, used the Apple Watch as a sensor to try to see if this type of device can be used as a reliable medical diagnostic tool but did not include the latest model, the only one capable of performing electrocardiograms.
The results complement Apple’s clinical tests – performed independently – and suggest that wearables or wearable electronics devices can be an important ally in the future for medical professionals. In 84% of the cases in which an irregular pulse notification was received, the patient presented atrial fibrillation at the time of measurement.
One of the concerns of doctors, however, is that this type of tool saturates the consultations of patients concerned about an alert received on the device that turns out to be a false positive or does not require urgent intervention. The study points out that this scenario is unlikely. Only 0.5% of the more than 400,000 participants received notification and only 57 of them sought medical attention.
Still, there are doctors who believe that these types of diagnostic tools may present problems and that the Stanford University study has not clarified the usefulness of this type of device. “Several types of arrhythmias were not identified and we have not learned anything particularly important from this study,” explains cardiologist Milton Packer.
Only in 34% of the participants who received a notification and accepted to wear a patch for electrocardiograms during the following weeks, an arrhythmia was detected, an expected result given that atrial fibrillation usually occurs intermittently.
Other doctors have also criticized the study as being unrepresentative of the real population . Requiring the use of Apple devices has introduced a bias in the universe of participants. 70% were white and 80% were younger than 55 years and only 13% had high risks of cardiovascular diseases.
Apple, in any case, has taken precautions when writing notifications to try to explain concisely what they mean, what importance they may have and what steps the user should follow. The language of them has been careful not to generate an unnecessary sense of alarm. The company has also indicated that it will continue working on new studies in collaboration with the medical community.