title: Exploring Physiologic Markers in the Identification of Vasovagal Syncope
Creators: name: Alsaleh, Mohammed Abdulaziz
Publisher: name: Cumming School of Medicine
Year: 2025
Subjects: subject: vasovagal syncope
subject: blood pressure analysis
subject: signal processing
subject: Head-Up Tilt
subject: beat-to-beat BP monitor
subject: Clinical trials
subject: Serotonin
subject: Bezold-Jarisch
subject: Hemodynamics
subject: Medicine and Surgery

description: Background: Vasovagal Syncope (VVS) is a common cardiovascular disorder, with at least 40% of individuals experiencing at least one episode in their life and about 20% of adults experiencing recurrent episodes. Traditional diagnostic methods such as the Head-Up Tilt (HUT) test and Implantable Cardiac Monitors (ICM) have significant limitations, including limited availability, high costs, and intensive resource requirements. A novel wearable, beat-to-beat blood pressure (BP) monitor is being developed to address these issues. This device, worn on the ear, samples BP at 50 Hz, stores and streams data, and features a rechargeable battery lasting up to 30 hours. This innovative solution will offer a cost-effective, user-friendly alternative for VVS management, potentially improving diagnostic accuracy and patient outcomes. Aims: We aimed to investigate the potential of a wearable beat-to-beat BP monitor in diagnosing vasovagal syncope. The thesis is structured around the following objectives: Objective 1: Provide a detailed narrative review of vasovagal syncope physiology, the Bezold-Jarisch reflex, and the need for a wearable beat-to-beat BP monitor. Objective 2: Validate the short-term blood pressure fluctuations during scripted physiological changes with a wearable beat-to-beat BP monitor. Methods: The narrative review explores physiological mechanisms underlying VVS, highlighting serotonin's role. For Objective 2 data were collected from 14 participants during activities such as rhythmic breathing and hand grips to validate the ear BP monitor. Spectral and coherence analyses assessed synchronization between the ear monitor and the Modelflow system, with non-parametric methods evaluating statistical differences. Results: The narrative review identified key markers for monitoring VVS. The narrative review identified key markers for monitoring vasovagal syncope (VVS), which guided the validation of the ear BP monitor. Data was successfully collected from 14 out of 20 participants, comprising 47% male and 53% female subjects, with an average age of 24.29 ± 5.61 years. The device demonstrated high coherence values (&gt;0.95) across all activities, indicating strong synchronization with the Modelflow system. No significant differences were observed in systolic BP measurements, with p-values of 0.37 for low-frequency components and 0.18 for high-frequency components, confirming the ear BP monitor's ability to capture BP fluctuations during dynamic physiological changes accurately. Further analysis identified the fundamental heartbeat frequency as 1.4 Hz, with harmonics at 2.8 Hz, 4.2 Hz, and beyond. The coherence of these harmonics highlighted the consistency of the heartbeat-induced waveform shapes, indicating that the arterial blood pressure measurements from the Modelflow and EarBP devices were stable and reliable. Coherence across frequencies revealed comparable signal synchronization between the two devices, with significant coherence observed at the fundamental frequency and its harmonics. Coherence values were tightly clustered near the median across all conditions, with the Valsalva maneuver showing slightly more significant variability due to lower coherence values in some participants. These results collectively validate the ear BP monitor as a reliable tool for arterial pressure measurement and synchronized waveform analysis. Conclusion: This thesis advances the understanding of vasovagal syncope (VVS) physiology and validates using a novel ear-based blood pressure monitor. The narrative review identified key physiological markers and mechanisms, including the Bezold-Jarisch reflex and serotonin signaling, central to VVS episodes. The validation study demonstrated high accuracy and synchronization of the ear BP monitor with established standards, offering a non-invasive, wearable alternative for real-time blood pressure monitoring. While promising, further research is required to expand its validation across diverse populations and address potential limitations such as motion artifacts. These findings support the use of an ear BP monitor as an innovative tool with the potential to diagnose vasovagal syncope.