A Wearable Dual-Band Radio-Frequency Sensor for Continuous Beat-to-Beat Left Ventricular Volume Monitoring

Objective: Real-time and continuous monitoring of cardiac volume offers transformative potential in cardiac health, yet its ambulatory and non-invasive assessment remains elusive. This work presents a novel dual-band near-field radiofrequency (NFRF) sensing system capable of extracting left ventricular (LV) stroke volume (SV), end-diastolic volume (EDV), and beat-to-beat LV volume morphology in real time using a fully non-invasive device. Methods: These measurements were validated against invasive LV conductance-derived volumes in an in vivo porcine model involving nine subjects undergoing physiological challenges to induce acute volume changes. Results: The NFRF sensor demonstrated a median SV error of \textminus0.22 mL (interquartile range: \textminus 2.09 mL to 2.60 mL) during vasoconstrictor bolus-induced SV decreases and achieved a Pearson correlation coefficient of 0.98 \textpm \space 0.01 compared to catheter-assessed EDV changes during caudal vena cava occlusion. Conclusion: These results demonstrate the capability of the NFRF system to track acute volumetric changes with high accuracy. Significance: Real-time ambulatory LV volume assessment can be transformative for numerous acute and chronic illnesses, including remote heart failure patient management and traumatic injury detection.