The Apple Watch Series 4 has been redesigned with a feature that could potentially disrupt the field of heart rhythm monitoring.

The redesigned watch includes a sensor that can take an electrocardiogram (ECG) reading in 30 seconds and classify whether the heart is beating normally or there are signs of atrial fibrillation (AF). The recordings are stored in the health app in a PDF file that can be shared with physicians.

It is important to diagnose conditions such as AF which can increase a person’s risk of stroke and can early blood thinning can reduce this to near zero. However, the potential for misdiagnosis is real and will likely spawn more referrals to cardiology to clear up whether or not there is a genuine arrhythmia – usually by performing more tests which carry their own risks. There is also a concern that the watch will detect short runs of AF, in younger patients who are otherwise fit and well – will blood thinners be appropriate in this low-risk group?