The Cardiac Caval Index: Improving Noninvasive Assessment of Cardiac Preload

Abstract

Objectives-Inferior vena cava (IVC) pulsatility quantified by the Caval Index (CI) is characterized by poor reliability, also due to the irregular magnitude of spontaneous respiratory activity generating the major pulsatile component. The aim of this study was to test whether the IVC cardiac oscillatory component could provide a more stable index (Cardiac CI-CCI) compared to CI or respiratory CI (RCI).Methods-Nine healthy volunteers underwent long-term monitoring in supine position of IVC, followed by 3 minutes passive leg raising (PLR). CI, RCI, and CCI were extracted from video recordings by automated edge-tracking and CCI was averaged over each respiratory cycle (aCCI). Cardiac output (CO), mean arterial pressure (MAP) and heart rate (HR) were also recorded during baseline (1 minutes prior to PLR) and PLR (first minute).Results-In response to PLR, all IVC indices decreased (P < .01), CO increased by 4 AE 4% (P = .055) while HR and MAP did not vary. The Coefficient of Variation (CoV) of aCCI (13 AE 5%) was lower than that of CI (17 AE 5%, P < .01), RCI (26 AE 7%, P < .001) and CCI (25 AE 7%, P < .001). The mutual correlations in time of the indices were 0.81 (CI-RCI), 0.49 (CI-aCCI) and 0.2 (RCI-aCCI).Conclusions-Long-term IVC monitoring by automated edge-tracking allowed us to evidence that 1) respiratory and averaged cardiac pulsatility components are uncorrelated and thus carry different information and 2) the new index aCCI, exhibiting the lowest CoV while maintaining good sensitivity to blood volume changes, may overcome the poor reliability of CI and RCI.

Processing Ultrasound Scans of the Inferior Vena Cava: Techniques and Applications

“…By filtering the IVC diameter in different frequency ranges, it is possible to isolate these two important oscillatory components and estimate different collapsibility indexes: the cardiac CI (CCI) and the respiratory CI (RCI). As expected, the CCI and RCI provide information that is, at least in part, uncorrelated [15].…”

“…Studies show that the cardiac component of IVC collapsibility is less affected by the spontaneous variability of respiratory pattern and is, therefore, a more-robust indicator [ 17 ]. A new, more-stable index for studying vessel collapsibility has been proposed as the averaged CCI over different respiratory cycles, known as the aCCI [ 15 ].…”

“…Different IVC segmentation methods have been proposed to track the movements and delineate the vessel walls by processing B-mode US scans [ 10 , 16 , 17 , 18 , 19 ]. Furthermore, these methods reduce the variability associated with the CI measurement [ 15 ].…”

Detection of Inferior Vena Cava in Ultrasound Scans through a Deep Learning Model

“…Our group introduced different methods to process US videos of IVC [13,14] supporting standardization and improving repeatability of measurements [37]. Some preliminary applications have been obtained [7][8][9]38,39]. However, our algorithms require a preliminary interaction with the user, so that our techniques can be considered semi-automated and results still depend on the operator's settings.…”