1003-3 Estimation of Mean Right Atrial Pressure in Critically III Patients Using Doppler Echocardiography

Abstract

Mean right atrial pressure (RAP) is a major determinant of right ventricular filling and is also needed for precise estimation of pulmonary artery pressures by Doppler echochardiography. Although ventricular and atrial Doppler filling parameters have been shown to relate to filling pressures, the majority of these studies have involved the left ventricle. To evaluate the accuracy of Doppler filling parameters in assessing mean right atrial pressure in critically ill patients, 35 patients (mean age 60 ± 15 yrs) in medical. cardiac and surgical intensive care units underwent simultaneous measurement of right atrial pressure and pulsed Doppler recording of tricuspid inflow and hepatic venous flow velocities. Thirty-four percent of patients were on mechanical ventilation. Mean right atrial pressure ranged between 2 and 28 mmHg (mean 9 ± 6). Left ventricular ejection fraction was 48 ± 15%. Of 6 tricuspid inflow variables, the strongest correlation with mean right atrial pressure was observed with the ratio of maximal early to late flow velocity (EIA) (r = 0.6). Among 8 variables analyzed from hepatic vein recordings, the highest correlation (r = –0.86) was seen with systolic filling fraction of hepatic vein flow velocity (SFF HV ; mean 0.53 ± 0.20) derived as the ratio of time velocity integral of systolic flow to that of systolic and diastolic forward flow. The best linear regression model correlating with mean right atrial pressure was: RAP = 21.6 – 24 SFF HV . This equation was tested prospectively in a group of 27 patients with a mean age of 64 ± 17 yrs and ejection fraction of 51 ± 14%. Mean right atrial pressure was 7 ± 5 (1–21 mmHg) and 41% of patients were on mechanical ventilation. Predicted mean right atrial pressure from SFF HV using the regression equation correlated well with observed pressure in this prospective group (r = 0.89). For the total 62 patients. correlation between observed and predicted right atrial pressure was 0.87 with a mean difference between predicted and observed pressures of –0.8 ± 2.2 mmHg. For mean right atrial pressure of > 10 mmHg, the sensitivity was 85% with specificity of 94%. Thus. mean right atrial pressure correlates significantly with right sided Doppler filling dynamics and is most reliably estimated in critically ill patients using Doppler echocardiography of hepatic venous flow.