Right Atrial Pressure Estimation

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Am J Cardiol. 1990 Aug 15;66(4):493-6.
Noninvasive estimation of right atrial pressure from the inspiratory collapse of the inferior vena cava.
Kircher BJ, Himelman RB, Schiller NB.
University of California, San Francisco, Division of Cardiology, John Henry Mills Echocardiography Laboratory.

To evaluate a simple noninvasive means of estimating right atrial (RA) pressure, the respiratory motion of the inferior vena cava (IVC) was analyzed by 2-dimensional echocardiography in 83 patients. Expiratory and inspiratory IVC diameters and percent collapse (caval index) were measured in subcostal views within 2 cm of the right atrium. Parameters were correlated with RA pressure by flotation catheter within 24 hours of the echocardiogram (38 were simultaneous). Correlations between RA pressure (range 0 to 28 mm Hg), expiratory and inspiratory diameters and caval index were 0.48, 0.71 and 0.75, respectively. Of 48 patients with caval indexes less than 50%, 41 (89%) had RA pressure greater than or equal to 10 mm Hg (mean +/- standard deviation, 15 +/- 6), while 30 of 35 patients (86%) with caval indexes greater than or equal to 50% had RA pressure less than 10 mm Hg (mean 6 +/- 5). Sensitivity and specificity for discrimination of RA pressure greater than or equal to or less than 10 mm Hg were maximized at the 50% level of collapse. Thus, IVC respiratory collapse on echocardiography is easily imaged and can be used to estimate RA pressure. A caval index greater than or equal to 50% indicates RA pressure less than 10 mm Hg, and caval indexes less than 50% indicate RA pressure greater than or equal to 10 Hg.

J Am Soc Echocardiogr. 1992 Nov-Dec;5(6):613-9.
Does inferior vena cava size predict right atrial pressures in patients receiving mechanical ventilation?
Jue J, Chung W, Schiller NB.
Department of Medicine, University of California, San Francisco.

The inferior vena cava diameter and its respiratory response are used to estimate right atrial pressures in spontaneously breathing patients but its value in patients receiving mechanical ventilation is unvalidated. Forty-nine patients undergoing mechanical ventilation were prospectively evaluated in the intensive or coronary care units with two-dimensional echocardiography of the inferior vena cava and simultaneous measurements of mean right atrial pressures by central venous or pulmonary artery catheter. Correlation between inferior vena cava diameter at expiration and mean right atrial pressure was only 0.58. The correlation between inspiratory change in inferior vena cava diameter and mean right atrial pressure was poor (r = 0.13). Despite these correlations, an inferior vena cava diameter of < or = 12 mm predicted a right atrial pressure of 10 mm Hg or less 100% of the time, but sensitivity was only 25%. An inferior vena cava diameter > 12 mm had no predictive value for right atrial pressure.

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