Smartphones are turning out to be an exciting weapon against the scourge of cardiovascular disease, which is considered by the World Health Organization (WHO) to be the most common cause of death worldwide.
Reasons for such a development are varied. Smartphones bristle with sensors like cameras and accelerometers which can be used for making, storing and transmitting diagnostic measurements. Smartphones are also small, mobile and capable of being paired with wearable devices such as wristbands, watches, skin patches etc.
Real-time and continuous measurement
The concept of always-on continuity, enabled by smartphones, makes sense in several cardiovascular health-related contexts. To date, most authoritative studies in this field are based on questionnaires, and focused on variables like diet, exercise, sleep etc. They have also relied almost wholly on participant recall.
By contrast, the sensors in mobile smartphones allow for real-time and continuous measurement of a range of factors. This can make a major difference.
For instance, high blood pressure (hypertension) is known to be a leading cause of strokes and heart attacks. However, blood pressure is very difficult to measure precisely. It can vary widely over just one day, and increase if one simply dangles one’s feet off a table, or for that matter becomes stressed by the exam itself. In this case, a wearable which monitors blood pressure through the day and night, and provides an average over time to compare with those from previous days or weeks, has clear advantages over the spot metric offered by blood pressure measurement at a physician’s clinic.
Applications in atrial fibrillation
Elsewhere, smartphone apps are now targeting the diagnosis of irregular heart rhythms, which can indicate atrial fibrillation (AF), another major cardiovascular risk. Such irregularities need not be symptomatic, but can be all the more dangerous because of that.
In 2014, the US Food and Drug Administration (FDA) approved the AliveCor Heart Monitor, which consists of a smartphone app plus a phone case fitted on its back with special sensors. Touching the sensors allows visualization of cardiac electrical activity on the phone screen.
Currently, a host of other smartphone apps alert users about potential AF without requiring any special sensor-equipped case. Though yet to be cleared by the FDA, reports suggest they might be similar in accuracy to AliveCor.
Migration from fitness to the medical
Another approach to arrhythmia has been taken by the Media Lab at the Massachusetts Institute of Technology (MIT). The latter’s Cardiio spin-off also illustrates the potential for migrating smartphone apps from fitness monitoring to the medical. In 2012, Cardiio launched an eponymous fitness app to measure heart rate based on facial light reflection, given that a beating heart pumps and increases blood volume in the vessels. On its part, blood hemoglobin absorbs light, and this decreases the amount of light reflected by the skin. Though such tiny changes in reflection are invisible to the human eye, they can be sensed by smartphone cameras and interpreted by apps.
Cardiio recently deployed its light-reflection system in another app, which detects the irregular heartbeat patterns of atrial fibrillation.
An electrocardiogram (ECG), which involves the attachment of electrodes to the chest to measure electrical impulses in a heartbeat and detect irregularities, remains the standard for AF-detection. However, as in the case of the blood pressure variations mentioned above, clinicians are aware that an ECG might not pick up an AF, should the heart rhythm irregularity be sporadic. Indeed, in some cases, irregularities are discovered only after patients suffer a stroke. One of the most common of these is known as paroxysmal AF, which causes spontaneous irregular heartbeats that are not straightforward to diagnose.
Supplementing traditions, new frontiers
In general, no one believes that smartphones will replace diagnosis by traditional medical devices. However, they have begun to supplement the latter, and are expected to continue doing so. Such a process is taking smartphones into ever-newer frontiers.
For example, engineers at the California Institute of Technology (Caltech) have demonstrated a smartphone app which measures ‘left ventricular ejection fraction’ (LVEF). LVEF is the volume of blood pumped by the heart per beat as the arteries expand and contract, and is one of the principal measures of heart health. It is typically assessed by ultrasound, which can take hours and be performed only by technicians.
The Caltech app requires patients to hold a smartphone camera against the carotid artery in their neck. This feeds directly into the heart and provides especially accurate information. The procedure, which lasts under two minutes, involves the camera measuring the expansion and contraction of the carotid artery’s walls. An algorithm in the app uses this data to calculate blood flow from the heart. According to some reports, the app provides LVEF data which is as accurate as an ultrasound.
Many industry experts foresee that next generation wearables will have ECG and pulse oximetry capabilities, with some going as far as predicting that wearables, supported by sensors embedded discretely in clothing, could be used for continuous blood glucose and blood pressure monitoring.
Part of wider mHealth drive
As smartphones begin to be seen as a strategy to fight cardiovascular disease, many manufacturers and app developers have sought to commercially capitalize on the wider mobile personal health (mHealth) movement. Indeed, it is now becoming accepted that mobile devices and apps can provide data to make meaningful and informed clinical decisions.
For some cardiovascular conditions, mHealth is also seen as enhancing the ability for pre-emptive intervention by giving patients more accessible diagnostic tools and information.
Indeed, CVD prevention represents an ideal zone for propagating and popularizing mHealth. Cost‐efficient and scalable approaches can yield large scale insights into behaviours shaping/adversely impacting on cardiovascular health. Such solutions, in turn, can provide the raison d’etre for interventions which seek to change risky behaviour.
To make this work in the long term, however, providers, payers and professional societies concerned with cardiovascular health need to closely partner with mHealth developers. So too should regulators, especially given the emergence of a growing body of evidence about the benefits of smartphone-driven mHealth – not least in areas such as cardiovascular health.
Universities join industry in research
Until now, the gap in conclusive evidence has largely been on the clinical side, and there have been calls for more research to see how viable – and valuable – such solutions really are.
In January 2017, the authoritative ‘Journal of the American Medical Association’ published the results of a smartphone-centric cardiovascular study in the US, with physical activity patterns tracked and identified through cluster analysis and correlated with self-reported disease. The study found that a pattern of lower overall activity with more frequent transitions between active and inactive states was associated with the prevalence of equivalent self-reported cardiovascular disease as a function of higher overall activity with fewer transitions.
The JAMA study also drew several other conclusions. The first was confirmation of the existence of a sufficiently large smartphone-using population, who could be engaged to demonstrate cardiovascular health status using smartphones. Secondly, it showed that large-scale, real-time data could be gathered from mobile devices, stored, transferred and shared securely. The authors also noted that more data than any previous collected about the standard six-minute walk test could be generated in weeks.
Industry is enthusiastically upporting these efforts. The Apple Watch app Cardiogram, for example, has presented results saying that it could diagnose atrial fibrillation with 97 percent accuracy. Cardiogram had collaborated with the University of California San Francisco as part of Heart eHealth, the largest study to date on mHealth and heart disease. Apple recently announced it would be partnering with Stanford University researchers to run a study targeted at investigating AF.
Europe launches apps aimed at patients and professionals
In Europe, the European Society of Cardiology (ESC) has funded the creation of two AF apps targeted at patients, and at healthcare professionals.
The patient app provides education on AF, including sections on pathology, symptoms, prognosis, associated co-morbidities, management strategies and practical self-care tips. It is also designed to present information on individual stroke risk and provide a personal health record and symptom diary. On their part, patients fill in sections about their relevant health histories, which can facilitate consultation when shared with their healthcare professionals.
The professional app is designed as an interactive management tool incorporating new ESC Practice Guidelines on AF, and allows both conventional viewing of guideline text and recommendations, as well as interactive treatment algorithms. It is also aimed at improving consultation efficiency, via the provision of a patient register, pre-filled with data supplied by the patient app mentioned above.
Need for caution remains
In spite of all the buzz around smartphones and cardiovascular health, several experts have also been urging caution.
Major issues include a lack of representativeness. The bulk of smartphone users, not least those willing to experiment with new apps, are young, while cardiovascular disease risks rise in older age groups. In the US, for example, only 12% of adults aged over 65 years are estimated to own a smartphone.
Some studies in Europe have found such trends to be reversing. For example, a survey by consultants Deloitte in the UK last year indicates that 71% of 55-to-75 year olds now own an app-capable handset, and this age group has seen a faster adoption rate than any other over the past five years. However, members of the demographic tended to use their smartphones less than younger people.
Finally, younger users can also be fickle, with a steep drop-off in engagement over time. One survey found that only 80% of consumers continued to use their wearables regularly after three months. Such factors can produce major risks for data integrity in a study.
The limits of mass consumer technology
Another problem is technology. In spite of dramatic progress in recent years, an Apple Watch is easy to cheat.
Accuracy is another drawback. One smartphone app to measure blood pressure required users to place a smartphone against their chest and a finger over the camera. However, it was discovered to have missed high blood pressure in as many as eight of 10 patients. This was also the problem with a phone case which sought to measure blood pressure at the fingertip, but studies were inconclusive about whether the case was good enough for use in a home environment.
Healthcare professionals point to some more serious limitations. Devices checking heart rates infer rhythms from the pulse, and it is possible to have a normal pulse with an abnormal heart rhythm.