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Background: Ultrasound measurements of the inferior vena cava (IVC) diameter (IVCD), together with its respiratory variation, provide a noninvasive estimate of right atrial pressure (RAP). However, there is a paucity of studies that have compared this technique with simultaneous catheterization. We explored the best cut-off values of IVC parameters for elevated RAP in comparison with RAP measured by catheterization.Methods and Results:We prospectively enrolled 120 East Asian patients who were scheduled for catheterization. The IVCD and IVC collapsibility index (IVCCI) were measured according to the current guidelines. The optimal maximum IVCD (IVCDmax) and IVCCI cut-offs for detecting elevated RAP (RAP ≥10 mmHg) were 17 mm and 40%, respectively. When we combined both in proportion to the guidelines, the sensitivity and specificity for detecting elevated RAP were 75% and 94%, respectively. When the cut-off values from the current guidelines (>21 mm and <50%) were applied, the respective sensitivity and specificity were 42% and 99%. Interestingly, the cut-off value of the optimal IVCDmax indexed by body surface area (11 mm/m 2 ) was similar to previous Western population data. When we combined both cut-off values (11 mm/m 2 and 40%), the sensitivity and specificity were 75% and 95%, respectively., Conclusions: The optimal absolute IVCDmax and IVCCI cut-offs to detect elevated RAP were smaller than those in the current guidelines. Indexed IVCDmax may be an IVC parameter that can be used internationally.