Although not as accurate diagnosing atrial fibrillation (AFib) as a medical-grade 12-lead ECG monitor, especially on edge cases, the Apple Watch single lead ECG (Electrocardiogram) is still able to accurately detect and diagnose the vast majority of AFib cases (QH). In one study using a 12-lead ECG as a reference device, researchers found that the Apple Watch ECG monitor could detect AFib with nearly perfect accuracy approaching 99% among roughly 600 subjects split evenly between those with and without AFib. Based on results like this, the Apple Watch irregular rhythm notification feature received FDA clearance for users 22 years and older with no prior history of AFib (Figure 1). Such a notification could be followed up by further testing to confirm the presence of AFib or some other heart arrhythmia.
This success may represent the beginning of the Apple Watch becoming increasingly important in the medical domain. Although conceived of as a consumer device, the Apple Watch is used by more and more doctors to evaluate certain medical conditions, most notably those related to the heart. A recent Wall Street Journal article describes this trend in an article titled: "Apple Watch Is Becoming Doctors’ Favorite Medical Device." In particular, it is being applied not only as a diagnostic tool but also to manage AFib even though not cleared by FDA to do this (WSJ):
"Doctors are using the Apple Watch as part of how they diagnose and help their patients manage disease—whether or not it’s been specifically approved for such applications by the Food and Drug Administration or other regulatory bodies....There’s a large and growing body of research on how the Apple Watch is being used informally in medical care, despite other approved devices being available to track the same metrics."
Informal use is also termed off-label use which describes how doctors will prescribe drugs for conditions that have not been officially approved by the FDA. For example, a cancer drug may have been approved to treat non-small cell lung cancer, but then a doctor may use it on a different tumor say a glioma brain tumor if there are reports in the literature of potential benefits even though there has not yet been a large clinical trial and application for this novel use case:
“From the FDA perspective, with few exceptions, healthcare professionals generally may choose to prescribe or use a legally marketed human drug or medical device for an unapproved or uncleared use when they judge that the unapproved use is medically appropriate for an individual patient,” says an FDA spokesman.”
More specifically, the FDA has cleared the Apple Watch to notify users without a history of atrial fibrillation about potential AFib episodes, but it has not cleared this notification function for those who have already been diagnosed (Figure 1). In other words, it can't be used to help AFib patients manage their condition. For example, based on the number of notifications a patient may decide to take less (or more) of a blood thinner as a precautionary measure. Or if alerted to an episode, the patient may go to the emergency room. Neither of these scenarios has been cleared by the FDA, but some doctors have recommended that their AFib patients get an Apple Watch to give them this additional information.
The above off-label use may seem limited, but in the big picture it is a harbinger of things to come. The Apple Watch is bristling with medical sensors, and there are plans to add even more. Importantly, it continuously gathers this medically-relevant information (e.g. heart rate, activity, etc.) which can be a gold mine for assessing one's physiologic state.
A major concern arising from the massive volume of data produced by Apple Watches and other wearables is the potential for a high number of false positive results. In the WSJ article, cardiologist Ethan Koster highlights that with tens of millions of these devices in use, the possibility of inaccurate alerts signaling potential health issues becomes significant. This could lead to an unprecedented surge of individuals seeking medical attention and undergoing potentially unnecessary and expensive diagnostic tests.
In response to this risk, regulatory bodies like the FDA must play a crucial role in ensuring the accuracy and reliability of medical devices. It is important to balance the potential benefits of wearable health technology with the need for accuracy and responsible implementation.
In summary, the Apple Watch possesses a bright future in the medical domain but with some caveats. Imagine an Apple Watch capable of diagnosing and monitoring a wide range of health conditions. This potential could be realized if the sensors are sufficiently accurate, the analysis of the sensor data has been clinically validated, and the resulting information is communicated in a timely fashion to medical professionals. The wealth of data collected by the advanced sensors of the Apple Watch could revolutionize personalized healthcare.
Figure 1. Irregular heartbeat notification on an Apple Watch. Some doctors have recommended off-label use of this notification for patients already diagnosed with atrial fibrillation (AFib) to help manage the disease by providing more information on AFib episodes.
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