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Move over Holter? Heart Monitoring in the mHealth Era

Posted on by Dr. Francis Collins

Man wearing a blue patch on his chest, another man wearing 5 patches and a monitor around his neck.

Caption: New patch (left) and traditional Holter (right) for monitoring heart rhythms
Credit: iRhythm Technologies (left); Misscurry,Wikimedia Commons (right)

There are thousands of “wellness” apps for smart phones and other mobile devices that will help you count calories, calculate your BMI, monitor your meds, boost your fitness routine, or quit smoking. These are now commonly referred to as “mHealth,” where the “m” stands for mobile technology. While these gadgets may encourage a healthier lifestyle, few of them have been tested rigorously for improved health outcomes over time, and they won’t necessarily keep you out of the ER.

Some of the most dramatic leaps in mHealth will arise when we have small, inexpensive wireless devices with sensors that can monitor your physiology—heart rate, blood pressure, blood sodium and glucose levels, breathing patterns, brain waves, and so on—and then transmit those data to your physician, who can then take actions that may spare you a trip to the hospital or even save your life.

Efforts to develop and test such innovative devices are already underway. In fact, I’d like to share the results of recent a clinical trial that compared a wireless adhesive patch designed to monitor the heart’s rhythms with more traditional technology [1]. The new monitor, which resembles a 2- by 5-inch adhesive bandage, is stuck to a patient’s upper left chest, where it detects and records heart beats. You can wear this water-resistant patch for up to two weeks while doing almost anything—eating, sleeping, walking, running, bicycling, even taking a shower!

But why would anyone want to wear it? One important reason is to detect irregularities in heart beats called arrhythmias. Those are particularly challenging to diagnose when they occur episodically and therefore aren’t captured during a visit to the clinic. Such abnormal heart rhythms, which may be sensed as palpitations, are often benign.  But if the heart is truly beating too fast or too slowly, serious consequences can result: dizziness, fainting, or even sudden death.

The classic way of measuring heart activity is an electrocardiogram (EKG)—either at rest or during a stress test performed in a medical setting. But arrhythmias aren’t known for performing on command, and we all know that walking on a treadmill in a doctor’s office for 15 minutes with electrodes attached to your body isn’t quite the same as experiencing physical and mental stress in daily life.

For more than 50 years, physicians have relied upon a portable device called the Holter monitor to record patients’ heart activity as they go about their everyday activities. This monitor uses five to seven electrodes attached to the chest to measure electrical signals from the heart and record the data on a device hung around the neck or on a belt. The Holter is typically used to record about 24-hours’ worth of heart activity and then has to be physically delivered to a cardiac center to be analyzed. The device can be worn longer if taped in place, but most people don’t like the way it feels and alter their lifestyles while wearing it. The ideal monitor would be something that people wouldn’t mind wearing for a week or two—because that’s how long it can take to detect some infrequently occurring, but potentially dangerous, arrhythmias.

In a new study, NIH-funded researchers from the Scripps Translational Science Institute, La Jolla, CA, compared the arrhythmia-detecting abilities of the classic Holter monitor with that of the new Zio Patch, an FDA-cleared wireless adhesive device made by iRhythm Technologies [1]. Researchers asked 146 patients who were referred for evaluation of cardiac arrhythmia to wear both types of monitors for 24 hours. The Holter was then removed and the volunteers were asked to continue wearing the adhesive patch monitor for as long as they could tolerate.

During the first 24 hours, the Holter detected about 15% more arrhythmia events than the adhesive patch: a difference that researchers attributed mainly to problems with the algorithm used to interpret the patch’s data rather than actual detection problems. However,  because patients could tolerate wearing the adhesive patch monitor for a relatively long period of time—about 11 days on average—the new device was ultimately able to detect a significantly greater number of arrhythmia events (96) than was the Holter (61).

Pretty amazing stuff, but it will take a lot more than sheer ingenuity to move these devices from the inventor’s bench into the real-world settings. That’s why NIH is encouraging researchers, technology developers, and software designers to pull together to find ways of not only creating, but rigorously evaluating the benefits and risks associated with mHealth technologies. A new health gadget may sound cool, but you’d want to know that it’s been shown to produce better health outcomes before you invest your money (and maybe even your life) in it. Another challenge that calls for research is how to maintain the privacy and security of mHealth data. How do we protect trial participants and ordinary consumers without adversely affecting research and quality of care? Who will set rules for mHealth data?

All of these are crucial issues to think about as we move ahead into this exciting new era of digital, personalized health care.


[1] Comparison of 24-hour Holter Monitoring with 14-day Novel Adhesive Patch Electrocardiographic Monitoring. Barrett PM, Komatireddy R, Haaser S, Topol S, Sheard J, Encinas J, Fought AJ, Topol EJ. Am J Med. 2014 Jan;127(1):95.e11-7.


Eric Topol, Scripps Translational Science Institute, LaJolla, CA

Arrhythmias. (National Heart, Lung, and Blood Institute/NIH “Spotlight on Research”)

Atrial Fibrillation. (NHLBI/NIH “Health Topics”)

NIH support: National Center for Advancing Translational Sciences 

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