From applications that diagnose irregular heart rhythms to cases of phones that aim to measure blood pressure, there has been a wave of technology that promises to use our everyday devices, smart phones and portable devices, to combat heart disease. But, why the health of the heart and how much can these devices really do?
Heart disease is the most common cause of death worldwide, according to the World Health Organization, so companies want to work on a problem that could have a big impact and bring a lot of money. Apple, for example, launched a study to identify irregular heart rhythms with its Apple Watch. In addition, many sensors and portable devices lend themselves especially well to help with cardiovascular problems, says Greg Marcus, a cardiologist at the University of California at San Francisco.
Heart disease is the most common cause of death worldwide
Many phones, for example, already have accelerometers that measure physical activity, such as steps taken, while devices such as Apple Watch and Fitbits use sensors to measure heart rate. This type of information is crucial when it comes to heart health. (These fitness trackers, however, are not very accurate).
Cardiac irregularities can be dangerous without causing obvious symptoms, so smartphones that can diagnose them could be useful as a prevention strategy. Technology companies are working hard on this, but the big gap is now on the clinical side, and there needs to be more research to see if these solutions are really valuable.
Here is a general description of the latest developments in this area:
IRREGULAR CARDIAC RATE
The most common irregularity of the heartbeat is called atrial fibrillation or atrial fibrillation. Afib happens when the two upper chambers of the heart do not synchronize with the two lower chambers, and can increase the risk of everything from a heart attack to kidney disease or dementia. But it can be difficult to detect. There are several sensors, such as the Zio or LifeWatch patch, but it is annoying to use them continuously. "If your watch can detect it based on the rates it could measure, then it could allow you to receive early treatment and prevent that stroke," says Eric Peterson, a professor of medicine at Duke University and a member of the American. Association of the heart.
Last May, the Apple Watch Cardiogram application presented results indicating that it could diagnose atrial fibrillation with 97% accuracy. Cardiogram had collaborated with Marcus, the UCSF cardiologist, as part of the Heart eHealth Study, the largest study in the field of mobile health and heart disease. And in November, Apple announced it would partner with researchers at Stanford University to carry out the Apple Heart Study to investigate the AFIB. (Stanford will collect data from Apple until January 2019).
Image: Courtesy of Cardiogram
All this is very promising, but smart watches also have their limitations. The Apple Watch, for example, is touted as an important health tool, but it is easy to cheat. And while smartphones are extremely common, few people have smart watches, and those who do are likely to be richer than the general population. With devices that use heart rate, the rhythm is inferred from the pulse, and it is possible to have an abnormal heart rhythm with a normal pulse, says Marcus. In addition, there is a great variability in the amount of readings you can get, depending on the movement and constant contact with the skin, and we need more research to understand how these devices can be used to make the information more accurate from the point of view doctor.
HIGH PRESSURE SANGUINEA
High blood pressure or hypertension can cause strokes, heart attacks and kidney failure. The problem is that blood pressure is notoriously difficult to take, even with standard cuff devices in your doctor's office.
Blood pressure varies a lot during the day and may rise if you are stressed or just hang your feet off the examination table. Therefore, having a portable device that can monitor blood pressure throughout the day, and even at night, would definitely help doctors better identify at-risk patients and find the right therapy. The biggest challenge, however, is accuracy, says Bruce Alpert, a pediatric cardiologist who has done many validation studies for manufacturers of automatic blood pressure devices.
"Many new methods of technology have been invented in the last five years, especially as smartphones have become smarter and smarter," he says. "To date, none of them has proven to be accurate."
This smartphone sleeve with 3D printing aims to measure blood pressure when a user presses a finger with a finger.Photo: A. Chandrasekhar et al., Science Translational Medicine (2018)
A smartphone application called Instant Blood Pressure, for example, asked users to place their smartphone against their chest and a finger on the camera to take a measurement. But it was discovered that it omits high blood pressure in eight out of ten patients. A new phone case says to measure blood pressure from the tip of the finger, but an early study did not really show if the case is accurate enough to use at home. And there's also a variety of wristbands to measure blood pressure, says Peterson at Duke. The problem is always the same: precision.
One challenge is that all these non-cuffed devices do not measure blood pressure per se, which is taken by squeezing an artery near your elbow, as has been done for decades. They measure the blood pulse on your finger or wrist, and then use algorithms to correlate those numbers with the measurement of traditional blood pressure. That approach leaves a lot of room for mistakes.
People must also be trained to take their own blood pressure correctly. At the doctor's office, you are asked to place your arm on a table at the same level as your heart, your back supported and your feet resting on the floor. That's because blood pressure can increase with the simplest movements. A wearable that takes action while you run to take the subway or cook dinner will not be accurate.
"The point is: stop measuring your blood pressure!"
Also, for people with hypertension, measuring blood pressure in itself can be stressful. Peterson says there is a joke among doctors: when patients take their blood pressure and see that it is high, they get stressed. Then they keep taking their blood pressure, and the numbers keep going up, because they get even more stressed. "The point is: stop measuring your blood pressure!" Says Peterson.
A portable device that gives a reading every hour could stress people, leading again to inaccurate results.
More than 30 million Americans have diabetes, which means that their blood sugar levels are too high. Over time, diabetes can damage the kidneys, nerves and eyes. It can also increase the risk of heart disease and stroke, especially since diabetes often comes with other risk conditions such as hypertension and obesity. In fact, adults with diabetes are two to four times more likely to die of heart disease than adults without the condition, according to the American Heart Association.
People with the disease have to regularly measure their blood glucose, regulate what they eat or even inject the hormone insulin if necessary. At this time, the way to do it is invasive: patients have to prick their fingers to draw blood or get a small tube that is placed under the skin to measure the glucose in the fluid between the cells.
Technology companies have been trying to create portable devices that can control blood sugar without the use of needles. Google worked on a contact lens to detect glucose in tears, but the project is moving slowly. And it was rumored that Apple was also developing a kind of wearable without a needle. "It's an incredibly difficult problem," Mark Rice, an anesthesiologist and diabetes expert from Vanderbilt University told The Verge last year. "Everyone thinks they have a way of doing it, and everyone, until now, has failed."
"Everyone thinks they have a way of doing it, and everyone, until now, has failed."
Glucose is a difficult molecule to detect, it has no distinctive characteristics. So, current tests use chemical reactions to convert glucose into a drop of blood into molecules that are easier to track. For starters, there is not much sugar in the blood, and if the levels go down dangerously, it will not spill into tears, spit, sweat or urine. So that makes any bodily fluid other than blood an unlikely candidate to measure glucose.
Scientists are looking for other innovative ways to detect glucose by observing how infrared light shines through a thin patch of skin, such as an earlobe, for example. By calculating how much light glucose molecules absorb or disperse, a device could measure blood sugar levels, at least theoretically. Analytical chemist Mark Arnold of the University of Iowa created this device and appears to be working on the skin of rats.
There's only one problem: "It's about the size of a small refrigerator," he told The Verge last year. "It's not a device that can work on someone's wrist."
OTHER CONDITIONS RELATED TO THE HEART
Earlier this week, makers of AliveCor KardiaBand, a sensor compatible with Apple Watch, presented results that indicate they can use a heart read to detect dangerous levels of potassium in the blood. (The US Food and Drug Administration has not yet approved KardiaBand for this purpose, although the company says it is working on it.)
This condition, called hyperkalemia, can be caused by diabetes, dehydration and chronic kidney disease, among other things. It can cause kidney and heart failure. In general, hyperkalemia does not cause obvious symptoms, but it interferes with cardiac activity, which can appear in an electrical reading of the heart (called an electrocardiogram or ECG).
The KardiaBand is a sensor that fits the Apple Watch wristband and can take an ECG and send that information to an application. The team trained its AI with a data set of 2 million ECGs linked to 4 million potassium values, all from Mayo Clinic. He learned to diagnose hyperkalemia with 90 to 94 percent accuracy.
Because people sometimes have hyperkalemia with a normal ECG, KardiaBand will not detect hyperkalemia for everyone, says William J. Brady, a professor of internal medicine at the University of Virginia School of Medicine. But in general, he says, hyperkalemia will produce an obvious abnormality in the ECG, and he has initiated treatments in patients based on the ECG before having a blood test to confirm. "I put a lot of trust and faith in the ECG in this regard," he adds, although novice doctors or those who are not used to reading ECGs may find this type of interpretation more difficult.
And last year, Caltech engineers showed that a smartphone app can accurately measure how much blood the heart pumps with each beat, called the "left ventricular ejection fraction" (LVEF), as the arteries expand and they contract. LVEF is an important measure of heart health and is usually evaluated by ultrasound. Ultrasounds take a couple of hours and only technicians can do it.
The application asked patients to hold a smartphone camera (an iPhone 5) up to their neck for less than two minutes. (The neck houses the carotid artery, which is fed directly into the heart, so the information there is the most accurate). The camera of the smartphone measures the expansion and contraction of the arterial walls and the algorithm within the application analyzes the information to calculate the flow of blood from the heart. The application was as accurate as an ultrasound, but not as accurate as a brain scan, which is the most accurate way to measure LVEF.
This technology could be very important for children receiving chemotherapy. Chemotherapy can affect the heart, so patients often need an ultrasound every two weeks to determine if the dose should decrease. But this can be difficult for those who could live in rural areas, or whose parents can not take them. "The idea here is to make sure that this type of diagnosis is available to the masses," says study co-author Morteza Gharib.
It remains to be seen if technology companies will be able to decipher the code behind the monitoring of the most challenging heart diseases. The future is definitely promising. But as more and more gadgets flood the market, it's important that these devices are tested properly to show that they really can work, says Peterson.
"At the moment, we are in a stage where technology advances much faster than what is used in practice, in tests," he says. Therefore, before buying a portable device and blindly trusting it to control your health, always make sure that the company has shown that the device is accurate. "Then, be careful, buyer!" Adds Peterson.
Additional reports by Rachel Becker.