In this three part series, we’ll look first at current screening strategies and some of the limitations that create an opportunity for emerging tools. Then we’ll dive into some of the tools that will define the next generation of atrial fibrillation screening. This is Part 1.
When it comes to screening for atrial fibrillation, there is little guidance currently from professional societies reflecting the historical lack of data demonstrating efficacy of traditional screening techniques. The ACC/AHA/HRS guidelines on atrial fibrillation management do not make reference to screening1. The ESC guidelines recommend opportunistic screening for patients above the age of sixty five2. In large part, this is related to the lack of data on effective screening strategies – a 2013 Cochrane review on screening for atrial fibrillation found one randomized controlled trial for inclusion3.
One of the simplest screening techniques is simply palpating a pulse; that’s the strategy evaluated in the SAFE trial by Fitzmaurice et al; its on the basis of that trial that the ESC recommendations are made. Here, pulse palpation as the initial screening modality proved to be as effective as EKG screening in detecting atrial fibrillation in outpatients over the age of sixty five. However, here were significant issues with the accuracy of pulse palpation as well as clinician interpretation of EKGs, even with trained healthcare professionals. Its also worth noting that about 50% of patients randomized to EKG screening and 65% of patients randomized to pulse screening actually completed it4.
And recently, two major clinical trials evaluated the use of continuous cardiac monitoring in patients with recent cryptogenic stroke. In the EMBRACE trial, patients were monitored for thirty days with a wearable event monitor5. In the CRYSTAL-AF trial, patients received an implantable Reveal XT loop recorder and were monitored for as long as a year6. In EMBRACE, about 10% of patients in the intervention arm were found to have atrial fibrillation, defined as episodes greater than 2.5 minutes, compared to 2.5% in the control group. As a result, the use of oral anticoagulant (OAC) therapy nearly doubled in the intervention arm. In CRYSTAL-AF, 12% of patients in the intervention arm were found to have atrial fibrillation, defined as episodes greater than thirty seconds, in comparison to 2% in the control arm at one year. There was a similar effect on the use of OAC therapy as that seen in EMBRACE.
There were also important limitations in more recent studies evaluating prolonged cardiac monitoring in post-CVA patients. In EMBRACE, the monitoring device was a chest band attached to a belt-clipped event recorder. Its worth noting that of the patients enrolled in prolonged monitoring, only about 60% of eligible patients completed the full four week monitoring period.
In contrast, CRYSTAL-AF used Medtronic’s Reveal XT implantable loop recorder was used; therefore compliance was far less of an issue. However, the list price of about $5,000 will likely to lead to a some difficult economics when it comes to cost effectiveness. In addition, there are complication risks when considering an implantable device. In CRYSTAL-AF, there was a 2.4% rate of device removal due either to infection or pocket erosion.
These trials both highlight interesting opportunities for improving detection of atrial fibrillation in a high risk population. When tied to the availability of novel OACs with improved efficacy and safety profiles over warfarin, that convergence creates a unique opportunity to make a big impact on the morbidity associated with atrial fibrillation.
The limitations of the screening modalities used in the trials described above are ones that can be addressed remarkably well with emerging mobile health tools. Usability and cost are two factors to which mobile health, as an industry, pays particular attention. In our next two pieces, we’ll look at some of the emerging tools that could be the go to strategies when it comes to screening for atrial fibrillation.