mHealth: Atrial fibrillation detection – App supports heart health

Atrial fibrillation is the most common type of persistent cardiac arrhythmia (irregular heart rhythm). Researchers estimate that 1.8 million Germans are presently affected by this disease. The condition is difficult to diagnose, frequently goes undetected and may result in a stroke. A new smartwatch medical app is designed to help patients detect atrial fibrillation before it’s too late.

In this MEDICA.de interview, Professor Marcus Dörr explains how the smartwatch app works, describes the gap this app could close in healthcare, and reveals why it is accurate and reliable.

Professor Dörr, how does the new smartwatch app work?

Prof. Marcus Dörr: The smartwatch we used in this study uses a so-called photoplethysmographic (PPG) sensor that records pulse signals. Many of today’s smartwatch models have this type of built-in sensor. It is based on light emission and reflection. You've probably noticed a glowing green light on the back of a watch. This sensor scans the pulse and detects the amount of blood flowing through your wrist – this is called photoplethysmography.

What are the advantages of this app for patients with cardiac arrhythmia?

Dörr: Unlike other methods, this app is essentially available all the time. You can wear a smartwatch night and day. Patients can regularly track and analyze their heart rate while they sleep. Another benefit is that the app is not restricted to an operating system. It also works with smartphones for both Android and iOS operating systems. The app is affordable and can also easily be used by high-risk patients.

The app is suited for smartwatch and smartphone use. How does a smartphone measure heart rate?

Dörr: The smartphone uses the built-in camera to monitor the heart rate. You simply place your fingertip on the smartphone’s camera. We all know that we can feel our pulse at our wrist and notice whether it is regular or irregular. Meanwhile, the smartphone is able to detect signals that are much more delicate and records a pulse wave. This is possible because the heartbeat creates a pulse wave as blood is carried to parts of the body. Basically, you can envision this as taking a video with the smartphone that records the pulsation of capillary blood flow at the fingertip. The heart rate is synchronized with the pulse. This film is being evaluated and the pulse waves are reconstructed and subsequently analyzed using mathematical algorithms. This analysis determines whether the heart rate is normal and whether there is any abnormality in the pulse wave that might indicate heart rhythm disturbances such as atrial fibrillation.

There has been a study to verify that the smartwatch app is able to accurately detect atrial fibrillation. What was the result of the study?

Dörr: The study concluded that the diagnostic accuracy of the app was very good compared to the so-called single-lead ECG. Patients with and without atrial fibrillation were accurately identified. This makes the app a promising method that could facilitate continuous screening in patients at an increased risk of arrhythmia.

A long-term ECG can detect an increased risk of atrial fibrillation. If the result is negative, a cardiac event recorder is implanted just under the skin of the patient’s chest for long-term monitoring. Why should patients use the smartwatch app instead of the implant?

Dörr: When atrial fibrillation is suspected in patients, the standard practice is a long-term ECG over 72 hours. You can also surgically implant a cardiac event recorder that is active over a longer period of time. The implant can also be used for other indications – to identify the cause of unconsciousness or fainting spells for example. However, once atrial fibrillation has been detected, it is typically immediately treated with blood thinners. Ideally, this lowers the patient’s risk of stroke. The diagnostic tests are usually complete once no atrial fibrillation has been detected.

One issue here is that a cardiac event recorder implant is very costly and is typically not covered by health insurance providers - at least not in Germany. Once the typical 72 hours have passed, this gap can be closed by using outpatient mobile monitoring options that are quite simple and affordable - like this app. Ideally, this allows the detection of atrial fibrillation without the use of invasive methods. From this vantage point, you might say that the app is a potential alternative to the implant.

How long will it take before the new smartwatch app can be used in routine clinical practice?

Dörr: The app’s smartphone version is already available on the market. Meanwhile, the smartwatch version still requires further clinical trials, some of which are already underway. They need to show that the smartwatch app is able to correctly detect more patients with atrial fibrillation than the conventional methods. We expect more results in early 2020.

There are a variety of healthcare application on the market today. Why should patients use this specific app?

Dörr: This app was developed by a startup company in Jena. The company’s objective is to only bring scientifically validated apps to market. Currently, there is a wide range of healthcare apps on the market. However, the problem is that patients usually don’t know whether these apps are science-based and have scientific validation. Meanwhile, the app we tested is supported by clinical trials that were conducted prior to its introduction, which makes it very unique. The benefit of this app is that it will only be launched if the scientific data supports its validity and reliability.