ESC 2022 – Preventicus gets halfway there

Using a smartphone app to monitor patients’ heartbeats can double the rate of detection and treatment of atrial fibrillation compared with conventional screening, according to a study presented at the ESC meeting at the weekend. But with no improvement in stroke or other outcomes yet proven, it is unclear how the research might affect the app’s developer, Preventicus.

The private German group has other problems. A vast trial set for next year will look at whether the Apple Watch – which is already FDA-cleared to detect abnormal heart rhythms – can help patients already diagnosed with AF to minimise use of blood thinners. And the perennial questions around how these apps are paid for will also weigh on Preventicus.

The EBrave-AF trial enrolled 5,551 people aged 50-90 without an AF diagnosis but who were at elevated risk of stroke. Participants were randomly assigned to six months of digital or conventional atrial fibrillation screening. Those in the digital arm downloaded Preventicus’s Heartbeats app to their own smartphone; the app measures pulse wave irregularities using the phone’s photoplethysmographic sensor – in simpler terms, the user places a finger on the phone camera lens and light is used to measure the pulse through the skin. 

Finger on the pulse

Subjects in the app arm measured their pulse in this way for one minute, twice a day for 14 days, then twice a week, with push notifications used as reminders. If an abnormal rhythm was detected, the user was posted a patch to record a 14-day electrocardiogram that they then returned by post.

The researchers evaluated the trace, and, if an arrhythmia was detected, sent the results to the study participant and asked them to consult their local physician. The doctor then made a treatment decision but was not involved in the study.

In the digital arm 38 subjects (1.3%) had newly diagnosed AF that led to their doctors prescribing oral anticoagulants, the study’s primary endpoint, versus 17 (0.6%) of those monitored via conventional means. This yielded an odds ratio of 2.12 and a p value of 0.01.

Subjects who did not reach the primary endpoint in the first six months were then invited to join a second study phase in which they would be crossed over into the other monitoring group; 4,752 participants did so. Again, digital screening beat conventional methods, with 33 subjects in the app group having newly diagnosed and treated AF, versus 12 in the control group. There the odds ratio was 2.75 and the p value 0.001.

The app is available for both Apple and Android phones; there are no data on whether it is equally accurate on both systems. 

Hard data

The importance of clinical data to back efforts to gain approval and reimbursement of healthcare apps has become increasingly obvious of late (Better Therapeutics banks on data and partnerships, August 18, 2022). But in Preventicus’s case, this data might not get it much further forward. 

For a start, apps to detect arrythmias already exist; the Apple Watch has been an approved medical device for four years now thanks to its ECG capabilities, and even that was not the first (Apple takes a bite out of Alivecor, September 13, 2018).

Arguably the Apple Watch is a more useful tool, since it can detect arrythmias in a passive way; all the user need do is switch the option on in the settings. Preventicus’s app requires what Professor Axel Bauer of Innsbruck Medical University, presenting the EBrave-AF data at the ESC meeting on Saturday, called “active willingness” to take repeated measurements. 

Secondly, and more importantly, none of these technologies has been proven to decrease the risk of stroke – the most damaging of AF’s sequelae. Prof Bauer concluded his presentation by saying that future studies would be needed to test whether digital screening for AF leads to better treatment outcomes. 

The React-AF trial is intended as a step in this direction. An academic trial slated for next year, React-AF will compare current standard of care – continuous therapy with oral anticoagulants – with short bursts of anticoagulant drugs taken only when an Apple Watch detects prolonged atrial fibrillation. The notion is that this should maintain the benefits of the blood thinners while limiting the risk of bleeding they carry – not to mention the expense. 

This is the kind of use to which passive surveillance, running constantly in the background on a wearable device can be put; it would not be possible with something like Preventicus’s app. 

Heartbeats is free to download, but operates on a subscription model – in the UK it costs £4.99 per month or £24.49 per year. It is not clear if reimbursement is available or whether users simply pay out of pocket. The EBrave-AF data are certainly unlikely to persuade payers to fork out.