Can smart watches and other fitness and wellness trackers do more harm than good for some people?

Investigators evaluated the functioning of CRT devices from three leading manufacturers while applying electrical current used during bioimpedance sensing. Bioimpedance sensing is a technology that emits a very small, imperceptible current of electricity (measured in microamps) into the body. The electrical current flows through the body, and the response is measured by the sensor to determine the person's body composition (i.e., skeletal muscle mass or fat mass), level of stress, or vital signs, such as breathing rate.

"Bioimpedance sensing generated an electrical interference that exceeded Food and Drug Administration-accepted guidelines and interfered with proper CIED functioning," explained lead investigator Benjamin Sanchez Terrones, PhD, Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, USA. He emphasized that the results, determined through careful simulations and benchtop testing, do not convey an immediate or clear risk to patients who wear the trackers, but noted that the different levels emitted could result in pacing interruptions or unnecessary shocks to the heart. Dr. Sanchez added, "our findings call for future clinical studies examining patients with CIEDs and wearables."

The interaction between general electrical appliances, and more recently smart phones, with CIEDs has been subject to study within the scientific community over the past few years. Nearly all, if not all, implantable cardiac devices already warn patients about the potential for interference with a variety of electronics due to magnetic fields -- for example, carrying a mobile phone in your breast pocket near a pacemaker. The rise of wearable health tech has grown rapidly in recent years, blurring the line between medical and consumer devices. Until this study, objective evaluation for ensuring safety has not kept pace with the exciting new gadgets.

"Our research is the first to study devices that employ bioimpedance-sensing technology as well as discover potential interference problems with CIEDs such as CRT devices. We need to test across a broader cohort of devices and in patients with these devices. Collaborative investigation between researchers and industry would be helpful for keeping patients safe," noted Dr. Sanchez Terrones.