Impact of Body Size on Inferior Vena Cava Parameters for Estimating Right Atrial Pressure: A Need for Standardization?

Background Inferior vena cava (IVC) diameter and its respiratory change, as determined using echocardiography, are commonly used to assess right atrial pressure (RAP). Despite the widespread use of the IVC approach for RAP assessment, the relations among body surface area (BSA), IVC diameter, and respirophasic change remain unclear. The aim of this study was to investigate the impact of BSA on IVC parameters for predicting elevated RAP. Methods Ninety consecutive patients undergoing right-heart catheterization or central venous catheter insertion were prospectively included. To investigate the impact of BSA on IVC parameters, patients were divided into higher and lower BSA groups by comparing individual BSA measurements with the median value. Optimal cutoff points of IVC parameters for detecting RAP of ≥10 mm Hg were defined using receiver operating characteristic curves. Results The median RAP and BSA were 8 mm Hg (range, 1-25 mm Hg) and 1.61 m² (range, 1.23-2.22 m²), respectively. In all patients, the optimal cutoff point for maximal IVC diameter (IVCD_max) and IVC collapsibility for the detection of RAP ≥ 10 mm Hg were 20 mm and 49.0%, respectively. The optimal cutoff point of IVCD_max for predicting RAP of ≥10 mm Hg was significantly larger in patients with higher BSAs than in those with lower BSAs (21 vs 17 mm, P =.0342). No differences in collapsibility indices were detected between the two groups. IVCD_max was larger in men (19 ± 5 vs 17 ± 5 mm in women, P =.0347) and weakly correlated with BSA (r = 0.35, P =.0007), whereas no relation was found between IVCD_max and age. However, the partial correlation coefficient of the entire cohort demonstrated that only BSA was still associated with IVCD_max after adjusting for age and gender (partial correlation coefficient = 0.32, P =.0020). Conclusions Body size, measured as BSA, is important to consider when IVC diameter is used to assess RAP. The optimal cutoff point of IVCD_max was 21 mm for patients with larger BSAs and 17 mm for those with smaller BSAs. However, the cutoff point of IVC collapsibility was not influenced by the difference of BSA.