Background: Evaluating right atrial pressure (RAP) is essential for managing cardiac diseases. Right heart catheterization (RHC) measures RAP directly but is invasive. In contrast, transthoracic echocardiography (TTE) provides a noninvasive estimate of RAP through inferior vena cava (IVC) assessment despite some limitations. The right atrial expansion index (RAEI) reflects right atrial compliance by measuring the relative increase in volume during the reservoir phase. This study aimed to validate RAEI as a noninvasive parameter for estimating RAP. Methods: We retrospectively enrolled 1,020 patients (728 in the derivation and 292 in the validation cohort) with various chronic cardiac diseases who underwent clinically indicated RHC and TTE within 24 hours. Right atrial pressure was measured during the RHC and defined as elevated when above 10 mm Hg. Right atrial expansion index and other TTE parameters were measured offline and blinded to RHC results. Results: In the derivation cohort, RAEI showed a logarithmic correlation with RAP (lnRAEI-RAP: r = −0.65, P < .001). The natural log of RAEI was an independent and additive predictor of RAP, outperforming clinical, hemodynamic, and echocardiographic parameters, including IVC assessment. The natural log of RAEI was more accurate than IVC assessment for identifying RAP ≥10 mm Hg (area under the curve lnRAEI, 0.840,;P < .001; optimal cutoff, lnRAEI <3.53); this finding was replicated in the validation cohort (area under the curve lnRAEI, 0.826; P < .001). Furthermore, lnRAEI <3.53 was confirmed as an optimal cutoff for identifying RAP ≥10 mm Hg in the validation cohort as well (sensitivity, 74%; specificity, 79%; accuracy, 78%). Finally, the equation RAP = 19.3 – (3.29 × lnRAEI) derived from the derivation cohort estimated RAP more accurately (−0.2 ± 3.1 mm Hg) than IVC assessment (1.5 ± 4.2 mm Hg) in the validation cohort. Conclusions: In this patient cohort, lnRAEI was more accurate than IVC assessment for noninvasive RAP estimation.
Genovese, D., Previtero, M., Prete, G., Strosio, M., Cernetti, C., Badano, L., et al. (2025). Comparison of the Right Atrial Expansion Index with Inferior Vena Cava Assessment for Echocardiographic Estimation of the Right Atrial Pressure. JOURNAL OF THE AMERICAN SOCIETY OF ECHOCARDIOGRAPHY [10.1016/j.echo.2025.09.005].
Comparison of the Right Atrial Expansion Index with Inferior Vena Cava Assessment for Echocardiographic Estimation of the Right Atrial Pressure
Badano L. P.;Muraru D.;
2025
Abstract
Background: Evaluating right atrial pressure (RAP) is essential for managing cardiac diseases. Right heart catheterization (RHC) measures RAP directly but is invasive. In contrast, transthoracic echocardiography (TTE) provides a noninvasive estimate of RAP through inferior vena cava (IVC) assessment despite some limitations. The right atrial expansion index (RAEI) reflects right atrial compliance by measuring the relative increase in volume during the reservoir phase. This study aimed to validate RAEI as a noninvasive parameter for estimating RAP. Methods: We retrospectively enrolled 1,020 patients (728 in the derivation and 292 in the validation cohort) with various chronic cardiac diseases who underwent clinically indicated RHC and TTE within 24 hours. Right atrial pressure was measured during the RHC and defined as elevated when above 10 mm Hg. Right atrial expansion index and other TTE parameters were measured offline and blinded to RHC results. Results: In the derivation cohort, RAEI showed a logarithmic correlation with RAP (lnRAEI-RAP: r = −0.65, P < .001). The natural log of RAEI was an independent and additive predictor of RAP, outperforming clinical, hemodynamic, and echocardiographic parameters, including IVC assessment. The natural log of RAEI was more accurate than IVC assessment for identifying RAP ≥10 mm Hg (area under the curve lnRAEI, 0.840,;P < .001; optimal cutoff, lnRAEI <3.53); this finding was replicated in the validation cohort (area under the curve lnRAEI, 0.826; P < .001). Furthermore, lnRAEI <3.53 was confirmed as an optimal cutoff for identifying RAP ≥10 mm Hg in the validation cohort as well (sensitivity, 74%; specificity, 79%; accuracy, 78%). Finally, the equation RAP = 19.3 – (3.29 × lnRAEI) derived from the derivation cohort estimated RAP more accurately (−0.2 ± 3.1 mm Hg) than IVC assessment (1.5 ± 4.2 mm Hg) in the validation cohort. Conclusions: In this patient cohort, lnRAEI was more accurate than IVC assessment for noninvasive RAP estimation.
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