Sudden death in the era of smartwatches

Waiting for the first media report

Smartwatches have evolved considerably over the past few years, from a device used mainly by athletes to a common consumer tool, and are becoming reasonably common in use, possibly 10% of the population of the United States having access to one.

This being the case, it is highly probable that at least one or two sudden deaths have occurred where the deceased was wearing a smartwatch. Presumably, the data from such a situation would be valuable in providing some clue as to cause of death.

It is remarkable that no cases have been reported up until now.

This 2020 study describes two cases where an Apple Smartwatch detected a potentially lethal arrhthymia. They comment:

The second function provided by the smartwatch is a single-lead ECG capture. Operation of the ECG requires the subject to activate the program and to touch the electrode on the device with the opposite hand. As shown in the cases described herein, the resulting recording may be of sufficient quality to make a provisional arrhythmia diagnosis in addition to changes in the QRS axis (the waveform on the Apple Watch is similar to precordial lead 1). The important point, however, is that activation of the ECG required the subject’s awareness of a symptom and the ability to perform at least 2 steps.

This 2021 study mentions the potential for smartwatches to be inaccurate in the instance of some arrhythmias, and describes the case of a 36 year-old woman whose smartwatch did not detect an arrhythmia, even while her heart rate was over 200 beats per minute. The authors point out that she was able to record the elevated heart rate using a pulse oximeter. They caution:

Patients using smartwatches for ambulatory heart monitoring should be aware that the absence of an irregular pulse notification does not exclude possible arrhythmias. The algorithm is designed to reduce the chances of incorrect HR readings; a common strategy is to stop recording when high levels of motion interference are detected. Unfortunately, this means that there is a high chance that a true cardiac arrhythmia will be interpreted as motion interference. It is essential to understand the limitations of these technologies to avoid inappropriate reliance on them for diagnostic purposes.