TOP2: Miniature Extravascular Aortic Sensor for Continuous Blood Pressure Measurement: In-vivo Validation Under Pathological Conditions

Abstract

Purpose of the Study: In individuals suffering from cardiovascular diseases, and especially in heart failure patients supported with left ventricular assist devices (VADs), the long-term monitoring of arterial blood pressure (ABP) holds significant value for assessing the disease progression, monitoring patient compliance, and evaluating the treatment efficacy. Hence, it is imperative to advance and extensively validate new, accurate and robust sensory technologies for this purpose. Methods: The present study aimed to evaluate the performance of a newly developed hall-based magnetic aortic sensor (HBSD) in monitoring arterial blood pressure (ABP) in conditions of low pulse pressures that simulate the hemodynamic conditions of VAD supported patients (Magkoutas et al, JACC: Basic to Translational Science, 2023). To this end, twelve acute in-vivo experiments were performed using pigs that were connected to a cardiopulmonary bypass circuit, and their hemodynamic state was regulated through adjustments to the support rate and pharmacological stimulation. In each experiment, two HBSDs were implanted, one in the ascending and one in the descending aorta. The reference ABP measurements were obtained using an intravascular fluid-filled catheter. Results: The pressure signal provided by the HBSD accurately captured the highly varying pressure profiles, regardless of the pressure level, CPB support level, and effective pulse pressure. The analysis of the difference between the end-diastolic (EDP), systolic (SP), and mean arterial (MAP) pressure values measured with the HBSDs and the reference sensors (Figure 1B) demonstrates that the HBSDs provide highly accurate measurements with a mean absolute error less than 5 mm Hg, except for two cases. Furthermore, the comparison of the entire dataset of the HBSD and the reference sensor during one of the in-vivo experiments reveals a high linear association between the two methods, confirmed by an intraclass coefficient higher than 0.95 (Figure 1C). The results of the Bland-Altman plot in Figure 1D also indicate that the developed HBSD has a mean bias of 0 mmHg, with limits of agreement approximately equal to 8.5 mmHg, compared to the reference pressure sensor. Conclusion: This study provides evidence supporting the accuracy of the proposed HBSD in measuring the ABP waveform in pathological and varying hemodynamic conditions. This constitutes a crucial preliminary stage in advancing the HBSD towards clinical utilization, thereby unlocking the valuable information contained in the ABP waveform and enhancing patient surveillance and therapeutic intervention in individuals supported by VADs.Figure 1. A) Implantation procedure and components of the hall-based aortic sensor. B) Boxplots of the difference between the end-diastolic (EDP), systolic (SP), and mean arterial (MAP) pressure values measured with the HBSDs and the reference sensors. C) The intraclass coefficient (ICC) with 95% confidence intervals for the ABP measured with the HBSD and the reference ABP. D) Bland-Altman plot with the representation of the mean difference, the limits of agreement (LoA) (dashed line) from −1.96s to +1.96s, and 95% confidence intervals (CI).