Factors influencing inferior vena cava diameter and its respiratory variation: Simultaneous comparison with hemodynamic data

Abstract

BackgroundUltrasound assessment of inferior vena cava (IVC) diameter and its respiratory variation is widely used to estimate right atrial pressure (RAP). Generally, the IVC distends as the RAP rises; however, there may be discrepancies between the values. Therefore, it is critical to recognize clinical factors other than RAP that may influence IVC measurements. MethodsWe obtained the IVC maximum diameter and IVC collapsibility index (IVCCI) simultaneously during right-heart catheterization in 71 consecutive patients. Then, we assessed various clinical and hemodynamic factors to elucidate the independent determinants of IVC measurements. Moreover, we tried to generate the regression equation to estimate mean RAP from the IVC maximum diameter and IVCCI. ResultsThe mean IVC maximum diameter and IVCCI were 15 ± 4 mm and 51 ± 15%, respectively. In stepwise multivariate analysis, the higher mean RAP (β = 0.52; p < 0.0001), the presence of significant tricuspid regurgitation (β = 0.31; p = 0.0005), a larger body surface area (β = 0.22; p = 0.0017), and younger age (β = -0.18; p = 0.049) were independently associated with the IVC maximum diameter. Only the mean RAP was independently associated with the IVCCI (β = -0.45; p < 0.0001). The regression equation (R2 = 0.43, p < 0.0001) was as follows: estimated mean RAP = 3.7 + 0.62 × maximum IVC diameter / BSA - 0.07 × IVCCI. ConclusionDistension of the IVC mainly occurs with elevated RAP. However, the presence of significant tricuspid regurgitation, a larger body surface area, and younger age are associated with the IVC maximum diameter, independently of RAP. Interestingly, IVCCI is influenced only by RAP.