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Increasing and Evolving Role of Smart Devices in Modern Medicine

Today is an age of rapid digital integration, yet the capabilities of modern-day smartphones and smartwatches are underappreciated in daily clinical practice. Smartphones are ubiquitous, and smartwatches are very common and on the rise. This creates a wealth of information simply waiting to be accessed, studied and applied clinically, ranging from activity level to various heart rate metrics. This review considers commonly used devices, the validity and accuracy of the data they obtain and potential clinical application of the data.

In case of an emergency presentation, such as a cardiac arrest, physicians can easily access this information on a patient's phone and directly call a patient's emergency contact to notify them of the patient's condition and obtain more history. A medical ID takes only a minute or two to set up, yet this feature is underutilised by both patients and clinicians. How far do we go with information on a smartphone-based medical ID? Is this a legal document?
What if a patient's medical ID states 'do not resuscitate'? These are questions that need to be addressed today because these scenarios exist. We must not only consider these dilemmas, but also those that have not yet presented themselves.
Patients are also able to enter their own biometric information (e.g. weight and BP) for storage and easy review (Figures 1 and 2).
Many scales and BP cuffs can automatically upload information to smartphones. Home BP monitoring is recommended for patients with hypertension, including the use of a BP journal to assist with ongoing management. 3 We have all had patients come into the clinic carrying a few scraps of paper with their BP readings on them. Now, for most patients, we can instruct them how to log these in their phones, solving the problem of patients who leave their paper-based BP log at home while rushing to make their appointment, because they rarely forget to bring their phone. In addition, such logging allows providers to see BP displayed as a graph over time, including ranges ( Figure 1), and allows for better identification of temporal trends in BP for safer and more effective titration of BP medication. It also more actively engages patients in their own healthcare and has the potential to help increase adherence.

Addition of Sensors to Smartphones
In addition to smartphones being able to acquire primary data, they serve as a hub allowing for additional sensors to be used. AliveCor offers a small hand-held device (Kardia), which allows for on-demand, single-lead ECG recording. The device is small enough to be attached to a smartphone or can easily be kept in a pocket or purse. Patients can record a 30-second Lead 1 ECG tracing simply by placing their fingers on the contacts. This tracing is then reviewed by an algorithm to distinguish AF or other heart rhythms from sinus rhythm. Combining physician review with the algorithm increases accuracy, especially in the case of AF. 4 To date, over 30 million ECGs have been recorded using the AliveCor device. Recently, AliveCor has released the Kardia 6L, which can record 6 leads in a simple-to-use device using just the hands and a thigh.
These devices could replace traditional ambulatory ECG monitoring in some patients with palpitations. Because the device is owned by the patient, they can keep it with them indefinitely, allowing for longer-term monitoring without using intermittent monitors for a patient trying to capture a rare episode of palpitations. In some instances, this may potentially save patients from having a loop recorder implanted. It can even be used in guest mode on a friend or bystander who may be having symptoms.

Smartwatches
Currently, smartwatches are perhaps the best additional sensors to be added to a smartphone. Smartwatches have grown immensely in popularity, and Apple quickly dominated the entire watch industry, not just the smartwatch industry. In fact, Apple shipped more watches in the last quarter of 2016 than the entire Swiss watch industry combined, including Rolex and Swatch. Apple Watch quickly became the leading device, with 49% market share in 2016. 5  Men's Health journal estimated that one in five Americans wears a fitness tracker. 6 These data confirm the large size of this sector in technology, and the eagerness to use such devices by the general public. This is where it becomes our responsibility as clinicians to help guide patients in using the devices effectively and to their fullest.
The addition of a smartwatch adds significant information without the need to carry a phone. A user with an Apple Watch, for example, will readily have metrics available, including steps, flights of stairs climbed, distance walked, stand hours, estimated energy expenditure (EE) and HR. These metrics are also available via Fitbit, Samsung and Garmin devices ( Figure 4).

Accuracy and Validity of Smartwatch Data
Prior to discussing the use of smartwatch data in daily practice, a review of accuracy is warranted, especially as it pertains to HR and EE. Several studies have shown that in sinus rhythm there was strong agreement between ECG HR and that recorded by the Apple Watch and Fitbit. 7,8 The Apple Watch demonstrated the strongest agreement with ECG across a variety of activities, including sitting, walking, running and cycling, within 5-10% of the ECG. In the setting of faster HRs and atrial arrhythmias, there was some underestimation of HR with smartwatches compared with ECG. Predictors of increased error in HR measurement include darker skin tone, larger wrist circumference and higher BMI. Several other studies have validated the accuracy of wrist-worn devices for HR assessment. [9][10][11] The data tell a different story regarding EE. Compared against a reference standard of indirect calorimetry by expired gas analysis, all wrist-worn devices tested had a large margin of error of approximately 27%, typically overestimating expenditure. 8  The inaccuracy of EE does not render this information useless.
A study with over 2,000 participants using Fitbits over 6 months showed that a higher number of steps per day and highly active minutes per week were predictors of increased weight loss. 13 For example, patients walking <5,000 steps a day lost an average of 3.7% body weight, whereas those who walked >10,000 steps a day lost an average of 9% body weight. These metrics are easily measured by any modern activity tracker, and it appears that there may be benefit in having patients track this information. Furthermore, we as healthcare providers may review this information quickly and easily, allowing us to help patients play an active role in their health while holding them accountable to reach achievable goals. The study by Painter et al. also demonstrated that a high frequency of weighins (three per week) was associated with increased weight loss at 6 months. 13 Such information is easily obtained by a scale at home and can be entered into health apps for easy tracking of progress, which is shown to correlate with achieving weight loss goals. 13 Smartwatches also use gentle cues to nudge the wearer to live a more active life. They provide stand reminders every hour to help reduce sedentary behaviour; they also keep an easily accessible historic log of activity levels, which opens the door to many clinical applications.
The use of step count has been studied as a potential marker of clinical improvement in treating patients with angina. 14 Another novel  PPG-based detection of AF has been validated with high accuracy. 15 A user can be notified that they may be in AF, and those with a Series 4 or 5 Apple Watch can immediately obtain a single-lead ECG right on the watch, for more accurate determination of the rhythm. "My Apple Watch says I may have AF," has become a chief complaint from patients arriving at the emergency department or general practice or cardiology appointments. There are presumed benefits to early detection, such as more effective stroke risk reduction and prevention, given that one in five patients presenting with ischaemic stroke is newly diagnosed with AF. 16 The recent Apple Watch Study demonstrated that the technology was rapidly mobilised to enrol over 419,000 participants in 8 months to determine whether the irregular pulse watch notification was able to identify AF on the watch and an ECG patch. 17,18 The notification occurred in 0.52% of participants, and AF was identified in 34% of the 450 who used the patch, resulting in a positive predictive value of 71%.
Although promising, there is concern about the potential for falsepositive heart rhythms, and increased testing and anxiety for patients, but this was prior to the release of the Series 4 and 5 devices and their built-in ECG confirmation of rhythm, which will improve positive predictive value. This technology is not intended to monitor the burden of AF. Knowing these limitations should not deter use, but rather encourage it in an appropriate manner.

Novel Applications
The use of smartwatches is most common in the young to middleaged population, but the advanced features of the Apple Watch Series 4 and 5 make it very appealing for use in the elderly, who are at increased risk for both falls and AF. When a fall is detected, the watch will display an alert that can be used to contact emergency services with a tap or may be dismissed if the fall was detected in error or assistance is not needed. The watch can also contact emergency services automatically if a fall is detected and there is no movement for about a minute. This feature can offer some piece of mind to families caring for members who may be alone and are at risk for falling, but the availability of this feature is probably not known to most family caregivers.

Limitations for Use
Limitations do exist, of course. The use of this technology is intimidating to some patients and physicians who may not consider themselves tech savvy and may not be comfortable reviewing these novel data sources. Patients need to be capable of understanding how to use the devices and apps and, unfortunately, the less likely users are often the same patients who may benefit the most from such monitoring, such as those who are less educated or some of the elderly population. As in every area of medicine, patient selection is key, and it comes as no surprise that frequent monitoring and availability of biometric data may be anxiety provoking for some. 19 These challenges should not be used as reasons to avoid utilisation.
As our population ages, we will continue to see more patients who are more tech savvy, and the proportion of patients uncomfortable with this technology should decline.
An additional limitation relates to the amount of data. There is, of course, the potential for artefact and false-positive abnormalities.
Furthermore, how do we deal with a potentially overwhelming number of patient requests to review biometric data? Data overload and patient misunderstandings in what this information means are certainly issues that will become more common, and as physicians we should be proactive in educating patients and setting achievable expectations.
In one study, 58% of smartphone users surveyed had downloaded a health app onto their device, with fitness and nutrition being the most common types of apps. 20 Not surprisingly, younger age, higher income and higher education level predicted higher-level use of such apps.
Obesity was also a predictor of the use of these apps, suggesting that this subgroup of users is interested in health improvement. Some concerns among users included cost, burden of data entry and security of health information. 20

Patient Recommendations
Because almost all patients carry a smartphone, as providers we can educate patients and encourage higher-level use of the devices they already have. A simple use may include showing a patient with poorly controlled hypertension how to enter home BP values into the iOS Health app for easy review at follow-up visits. Patients seeking to improve their fitness level may use smart devices to track activity and progress with real-time feedback.
A HR monitoring smartwatch may be helpful for patients who have AF, especially with rapid HR or palpitations, because it would allow for simple, continuous HR monitoring. A Fitbit or Garmin account may be accessed from a computer or other smartphone, allowing for remote monitoring of HR and activity data. This may be particularly useful for family and caregivers to keep an eye on elderly loved ones. Smartphones and watches also have shortcuts to allow easy access to emergency services, as noted above.
Of course, this is not an exhaustive list of uses, but rather the tip of the iceberg.
Although this is not intended to be a product review, it is important for clinicians to be familiar with common devices, their limitations and how to combine the cost and feature set of the watch to help patients select a device that will serve them well. In general, the Having a smartwatch capable of constant HR monitoring is becoming the norm, and the technology continues to evolve. There are prototypes of wrist-worn devices that can sense radial artery pulsation and use the data to estimate central aortic pressure (e.g. BPro Cardio Pulse-Wave Device). Further work is being done to extrapolate BP from PPG-based data and blood glucose via optical sensors of various wavelengths. It is quite plausible that, in the not-too-distant future, a smartwatch will be capable of reading HR, rhythm, BP and blood glucose, all non-invasively and in the background.

Conclusion
Only a few years ago it was hard to believe that a smartwatch no larger than a typical watch would be able to make phone calls, send and receive text messages, track sleep and activity, record HR in the background and record a single-lead ECG, but this technology is readily available and becoming increasingly affordable. In addition to their amazing capabilities today, these devices hold great potential for tomorrow as technology advances, allowing for more capabilities while we continue to study and learn how to use these metrics to improve patient care. This is the new era of medicine, and there is a plethora of untapped information waiting to be studied and applied. Limitations do exist, but they are recognisable and not prohibitive to use.
Perhaps 'physical examination' should now include looking for and asking whether patients are wearing a smartwatch and exploring and recording the data reported on these devices. Device interrogation now has a new meaning and is no longer limited to pacemakers, ICDs and loop recorders. This opportunity to pick such low-hanging fruit should not be missed. The information is there; we simply need to know how to review it. It is our responsibility as clinicians to understand the meaningfulness and limitations of smart devices and to be able to counsel our patients and use this information in daily practice. Not doing so leaves a wealth of unused information and potential on the table.