Non-Invasive RF Technology Enables Long-Term Cardiac Monitoring

Cardiovascular diseases (CVDs) are the leading global cause of death, responsible for approximately 17.9 million deaths each year. The growing aging population has further contributed to the rising prevalence and mortality rates associated with CVDs. Studies show that early detection and timely intervention can significantly reduce the occurrence of cardiovascular illnesses. However, current detection methods such as electrocardiograms (ECG) and Holter monitoring are accurate but have limitations. The electrodes used in ECG and Holter devices can cause discomfort, making them impractical for long-term use. While wearable devices offer greater convenience, they tend to be less precise and more susceptible to environmental interference. Now, researchers have made a significant advancement in cardiovascular monitoring with the development of a non-invasive radio frequency (RF) based system that can accurately measure heart rate variability (HRV) over extended periods.

The RF-HRV system, developed by a team at the University of Science and Technology of China (USTC, Anhui, China), addresses interference caused by respiratory motion in far-field conditions by analyzing RF signals. The system utilizes a signal selection algorithm that identifies signals containing rich heartbeat information from multiple reflected sources. It then applies the variational mode decomposition (VMD) algorithm to extract high-frequency components, enabling the system to accurately capture clear heartbeat patterns. By combining adjacent heartbeat harmonics, the system generates specific patterns corresponding to the heart rate, which are then used to calculate HRV.

In addition, the researchers tested the system in a large-scale outpatient setting involving 6,222 participants, as well as in a long-term daily scenario involving continuous multi-night sleep monitoring. The study, published in Nature Communications, demonstrated that in the outpatient setting, the system's median real-time inter-beat interval (RT-IBI) error was 26.1 milliseconds, and in the daily monitoring scenario, the error was 34.1 milliseconds—both showing significant improvements over existing systems that focus only on signals from the heart rate frequency band. The system also performs well in automatically detecting heartbeat abnormalities and offers performance comparable to clinical-grade 12-lead ECG systems.

This study's innovation lies in its departure from traditional signal processing methods. By utilizing high-frequency ranges, beyond 10th-order heartbeat harmonics, the system effectively isolates heartbeat signals and overcomes the challenges posed by respiratory motion interference. This breakthrough establishes a strong foundation for the use of millimeter-wave radar in cardiac monitoring, enabling long-term, non-invasive monitoring without the need for electrodes or frequent adjustments. This advancement promises to provide a more comfortable, practical solution for cardiovascular care.