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It has been over 100 years since the first ECG was recorded, yet it is only in the past few years that the evolution of mobile health technologies has led to a change in the way that ECGs are recorded, stored and used. In 1901, Willem Einthoven published his work on the string galvanometer,1 a device that required a person to place an arm and leg in baths of saline. The device weighed 600 pounds, occupied two rooms and required five personnel to operate it. It took several decades before the device became small enough to move to a patient's bedside and to make the 12-lead ECG become a vital part of cardiac diagnostics.
Recently, the miniaturisation of computing technology has led to the invention of small handheld ECG devices that allow a quick rhythm analysis on a patient in the clinic. These devices have been of variable quality and with limited battery life, storage and review options.
In 2007, the launch of the Apple (California, USA) iPhone transformed the smartphone market and led to a change in the way that we use our mobile phones. Current devices have more processing power than desktop computers of just 12 years ago. It is estimated that in 2014 there were around 1.75 billion smartphone users in the world and 100 000 mobile health applications available for download.
In 2008, Dr David Albert (the former chief clinical scientist at GE Cardiology) predicted that the smartphone would become an ubiquitous disruptive technology. He created the AliveCor (California, USA) Heart Monitor that could record a single-lead ECG through a case that attached to a smartphone (figure 1). In July 2014, AliveCor announced that more than one million ECGs had been recorded using their devices in the 18 months since the device was launched.
One of the interesting features of the device and software is a cloud-based storage system. As soon as you make a recording, the data are transmitted online to a user account, using either the phone's data connection or Wi-Fi. The ECG recordings can then be reviewed, printed or shared by email. Automatic software algorithms can detect atrial fibrillation (AF). Even more helpfully, the user can be invited to link their account to their cardiologist's account so that they can share their recordings along with relevant clinical information (eg, time, symptoms, medications).
We have been using the AliveCor in clinical practice since it became available in the UK in early 2013. There are a number of clinical scenarios where we have found it particularly useful. Take a common clinical encounter of a young patient with infrequent but symptomatic palpitations and negative Holter. Although we may be suspicious of a re-entrant tachycardia the patient often does not have the monitor on, or has an ECG recorded during an attack. Instead of further prolonged monitoring or implantable devices we can now recommend a device that the patient can make recordings with. They always have their phone with them so now they always also have an ECG event recorder at hand. Patients take responsibility for capturing an episode and alert the provider, once they have uploaded a recording, for the ECG to be evaluated remotely (figure 2). This type of use will undoubtedly result in fewer clinic visits and lower the cost of monitoring while increasing the speed and accuracy of diagnoses.
Other potential uses include monitoring the patient with intermittent giddiness or presyncope who can be rapidly diagnosed to have bradycardia and therefore receive early definitive treatment with a pacemaker prior to sustaining injury from syncope (figure 3).
After catheter ablation, patients occasionally have symptoms of palpitation that are usually innocent but can sometimes be due to an arrhythmia recurrence or a new arrhythmia. It can be frustrating trying to chase these symptoms using conventional ECG monitors and event recorders, but devices such as AliveCor allow the patient to take charge of their medical symptoms and diagnosis. A series of recordings can be made and the cardiologist alerted by text or email when they are ready for review. This can take place at a time of the clinician's choosing and can obviate the need for further direct clinical contact.
Additionally, asymptomatic patients noted to have an irregular pulse in the community can be screened quickly using a physician's or nurse's device. Several screening projects have shown that these handheld ECGs can identify silent AF in the general population (figure 4).2–4 This is of particular importance given the morbidity of cerebrovascular events that often occur as a result of previously undiagnosed atrial arrhythmias. A diagnosis of AF can now be made within seconds, resulting in immediate patient counselling and arrhythmia management.
A rapidly growing number of digital health devices are coming into the market. Thanks to new data acquisition technologies, people are able to measure multiple modalities of their daily life using devices such as wearable sensors, cameras, data-loggers and Global Positioning System. Companies including Apple, Google, Microsoft and Samsung have all launched digital health platforms to try and entice new users, software and hardware developers. A recent report from PricewaterhouseCoopers suggests that one in five Americans owns a wearable device and one in ten uses them daily.5 The majority of the people surveyed used these devices to track and collect health information. The worldwide financial impact of these technologies is enormous with revenues from sports, fitness and activity tracking devices expected to be worth US$1 billion in 2014 with predicted growth of nearly 50% by 2019.
So how will the mobile ECG fare hereafter? The recent launch of wearable watch technologies that can link digital health devices may result in the next step in health and ECG monitoring. Embedded sensors can help record heart rate profiles and trigger alerts during periods of suspected arrhythmia, bradycardia and tachycardia. Biosensor patches may perhaps permit single lead recordings using locally linked disposable devices for continuous multilead ECG analysis. These data may link to sophisticated data centres offering patients diagnostic and treatment options. Patient portals will continue to become acceptable ways for patients to store their medical information and share their results with clinicians around the world.
As algorithms for the analysis of ECG rhythms become more sophisticated, the applications or devices themselves may soon be offering highly accurate diagnoses and treatment options without the need for clinician input.
At the moment, patients ask their doctors, but soon they may be asking their devices.
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