Inferior Vena Cava Edge Tracking Echocardiography: A Promising Tool with Applications in Multiple Clinical Settings

Figure 1. Recordings from a healthy subject: from top to bottom, cardiac component of IVC pulsatility (Dc-IVC), respiratory component (Dr-IVC), unfiltered IVC pulsatility (D-IVC), arterial blood pressure (ABP), respiratory movements (Resp), long axis IVC imaging was processed according to Mesin et al., 2019 [24].

Figure 2. Critical issues on RAP estimation by using IVC diameters. Top left: different breathing manners studied with US M-mode of the diaphragm. Top right: different proposed sites of measurement of the IVC. Bottom left: effect of the vein movement on the IVC diameter measurement showing foreshortening of the vein due to the respiratory cycle (A: latero-lateral displacement, B: cranio-caudal displacement) [12]. Bottom right: causes of unreliability of the IVC in RAP estimation [2]. Center: the proposed new IVC edge-to-edge tracking technique (adapted from Blehar et al. [12] and Wallace et al. [27]).

Figure 3. Panel (A): IVC tracking technique: the software is able to identify the vessel (IVC long axis view) (top) of interest and perform the edge tracking of five fixed points along both edges of the vessel (bottom). Panel (B): the results of the edge tracking techniques are shown: respiratory (top) and cardiac (bottom) components are represented. (Bold line graphic on top: respiratory component of the IVC diameter variation (mm). Bold line graphic at the bottom: cardiac component of the IVC diameter variation (mm). Non-bold line in both graphics: IVC diameter variation during two breaths). Panel (C): a US IVC scan in short axis view is shown; red arrows indicate the direction of the collapsibility of the vessel walls that is not directed in an antero-posterior way, rather the main direction is medio-lateral. Panel (D) shows a possible solution to perform a more reliable IVC study: the use of the three-dimensional x-plane echocardiography, to gain the possibility to evaluate in real-time both long and short axis views (adapted from Mesin et al. [8]).

Figure 4. Our edge tracking technique could be applied in multiple clinical settings (see the text for further explanations).

Figure 5. Main advantages that could be provided by an extensive use of US IVC edge tracking echocardiography (see text for further explanations).