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In this 3-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 3.

Atrial fibrillation is an increasingly prevalent arrhythmia; it currently affects 3 to 6 million of Americans and that number is expected to rise. And unlike many other medical conditions, it is often silent until discovered either incidentally or after a serious complication like a stroke.

Recently, the and trials looked at the use of continuous long-term cardiac monitoring in a high-risk patient population -- individuals with recent cryptogenic cerebrovascular accident (CVA). Both trials found an increase in the detection of atrial fibrillation as well as the use of oral anticoagulant therapy.

There were however notable limitations in the screening strategies used. In EMBRACE, patients had to wear a cumbersome chest strap with several wires attached to a belt-clipped event monitor. Not unexpectedly, the compliance rates were less than stellar. In CRYSTAL-AF, the $5,000 price-tag of the Reveal XT monitor coupled with its complication rate, albeit low, are important limitations when considering whether this strategy can be applied on a large scale.

Here, we'll look at some of the growing cadre of wearable devices that can provide continuous cardiac monitoring options to address those limitations.

Low Profile, Durable

There are a number of emerging options that have become available that could help address these concerns by using low-profile, wearable patches. While there isn't yet much data available in using these devices for atrial fibrillation screening, they certainly have advantages when it comes to their cost and the burden imposed on patients compared with Holters and event monitors.

One option is the . A low-profile patch free of wires or a bulky controller unit, the monitor is certainly sleek in appearance. The elegantly designed Zio patch is also water resistant and can be worn for up to 14 days. It includes a button on the patch that patients can use to mark symptoms and events. The Zio is mailed back to iRhythm for processing and interpretation.

A similar option is the , now owned by Medtronic. Also water-resistant with a low-profile design, Piix patch is another great example of a usable device. The device also includes a button on the patch that allows patients to mark events and symptoms. Data collected by the patch is then transmitted wirelessly via a base station usually kept at home. Now that the company has been acquired by Medtronic, the data can be captured through the CareLink telemonitoring system used for Medtronic's other implantable devices.

Unlike Zio and Piix which are both single-lead monitors, the from a company based in Australia provides a three-lead tracing. While the design is larger than that of the Zio or Piix, it does shed most of the wires of traditional Holters and event monitors. It's also waterproof. Similar to to the Piix patch, data is transmitted wirelessly via a cellular-enabled controller unit. The V-Patch can be worn for up to 7 days at a time. Currently, the V-Patch is not available in the U.S. although it has received 510(k) clearance.

The common feature among these devices is their design. All place a premium on low-profile design to help drive compliance with prolonged monitoring. To be fair, these device are not without their issues. For example, they rely on adhesives to stick the skin, which carries obvious challenges. And while they do attempt to embrace connectivity, both the V-Patch and Piix require a separate unit to collect and transmit the data even if that entire process is wireless. However, the here may make those weaknesses far more palatable -- the Zio patch runs about $500.

The Gap Between Detection and Benefit

With any screening modality, both the accuracy of the technique and reaching as many appropriate patients is critical to making a meaningful positive impact on health. These devices can help lower the cost of screening, increase the penetration of screening programs, and improve compliance with screening. The benefits, however, rest in the systems built around these screening programs to help shorten the loop from detection to intervention. The value of detecting atrial fibrillation is lost if patients aren't started on anticoagulation and other appropriate therapies.

There are a variety of strategies that could be employed to help achieve that benefit. For example, trying to focus screening efforts on patients who are eligible for anticoagulation could help simplify the process of initiating therapy after detection. Similarly, pairing screening with multimodality educational material to help patients understand atrial fibrillation and the associated risks and benefits of therapy could allow patients in whom atrial fibrillation is detected to make informed decisions more expeditiously about starting anticoagulant therapy.

So while there is a great deal of hype around many of these devices, much work remains to be done to help realize the promise they hold.

Med Tech Review, a look at mobile apps and other technology useful in clinical practice, is produced by in partnership with 番茄社区.

Satish is a cardiology fellow at the Johns Hopkins Hospital in Baltimore. He is a founding partner and managing editor at iMedicalApps. He believes that mobile technology can change the way healthcare is delivered and that iMedicalApps is a platform through which clinicians can be empowered to lead the charge.

From the American Heart Association:

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