118: Assessment of respiratory variation on inferior vena cava by three-dimensional echocardiography

Abstract

Accuracy of measurement of inferior vena cava (IVC) respiratory variations has clinical implications in the management of cardiac disorders because it affects the estimation of right-atrial (RA) pressure. We assumed that 3D can added more valuable information in IVC assessment. To develop a methodology of 3D exploration of VCI and evaluate it in comparison with 2D. 20 patients with good echo-visualisation underwent 2D and 3D (Philips IE 33). In 2D, the IVC maximal (2DDmax) and minimal (2DDmin) diameters was measured according to the ASE guidelines. In 3D, VCI was displayed according to its longitudinal axis, from the junction with the RA. Cross-section of the VCI was realized immediately after the hepatic vein junction. The large (D1) and small (D2) diameters and the surface (S) of this cross-section were measured when the VCI has the maximal size during normal respiration (maximal VCI dimensions). After deep inspiration, the same measures were done (minimal VCI dimensions). The IVC collapsibility index was calculate in 2D and 3D. 2DDmax and 2DDmin was 21.3+3.1 mm and 11.4+1.7 mm. 3D shows that VCI in cross section has an oval geometric shape. D1max and D1min was 27.6+1.9 mm and 22.3+1.5 mm. D2max and D2min was 15.6+1.2 mm and 11.1+1.1 m. S max and min was 3.2+0.6cm 2 and 2.0+0.4cm 2 . 2DD is less than D1 (p<0.001). Because VCI moves during respiration (outside of the initial 2D section), the physician can not conclude about the real diameter decrease and as a consequence 2D overestimated its respiratory variations. 3D allows true measurements by using the planes permanently adjusted in the space to anatomical landmarks. Because reflecting both long and short diameters, the surface of the cross-section of the VCI must be the more informative measurement. This study developed a 3D methodology of reliable assessment of the VCI. We propose for evaluation of respiratory variation of IVC an index of collapsibility of the surface of its cross-section.