Accuracy of right atrial pressure estimation by transthoracic echocardiography

Abstract

Abstract Background/Introduction Transthoracic echocardiography provides an estimate of right atrial pressure (RAP) using the guideline-recommend method of measuring inferior vena cava (IVC) diameter and collapsibility. Despite being ubiquitously reported and necessary for the estimation pulmonary artery systolic pressure, the accuracy of this method for RAP estimation has not been rigorously validated. Purpose To evaluate the accuracy of the guideline-recommended method for the estimation of RAP by TTE. Methods A single center, retrospective chart review of patients who had a TTE and right heart catheterization (RHC) within 48 hours of each other from January 2018 to December 2020. Maximum and minimum IVC diameter were measured by trained study personnel. Accuracy was then stratified by the presence/absence of a history of two variables that could modify IVC diameter independent of RAP—syncope, which is associated with more dilated IVC in some studies and liver disease, which could result in compression (from parenchymal fibrosis surrounding the IVC) or dilation (from diversion of portal blood flow through the IVC among other mechanisms) of the IVC. Results The 117 patients who met inclusion criteria had a median age of 67 years old (interquartile range [IQR] 58 – 75) and median RAP of 13 mmHg (IQR 8 – 18) on RHC. The median time between TTE and RHC was 9.6 hours (IQR 3.8 – 24.5 hours) during which 24 (20.5%) patients received intravenous fluids (median 220 mL administered; IQR 145 – 320). Forty-three (35.9%) received diuretics between the studies with most patients receiving either 1 (26 patients, 61.9% of those who received diuretics) or 2 (13 patients, 31.0%) diuretic doses. In evaluating accuracy, only 26 patient’s (20.5%) RAP by RHC fell within estimated RAP range by TTE (Figure 1). After excluding the 60 patients who received fluids and/or diuretics between the TTE and RHC, the TTE estimate was still only accurate in 13 (22.8%) patients. When analyzing how each subcomponent of the TTE guidelines for RAP estimation correlated with RAP via RHC, maximum IVC diameter and percent collapsibility had Pearson’s correlation coefficients of 0.47 and 0.24 respectfully (Figure 2A and 2B). Past medical history was significant for syncope in 16 patients (13.7%) and liver disease in 8 patients (6.8%). Compared to those without each factor, the absolute accuracy of the TTE estimate was lower when stratified by a history of syncope (12.5% accurate vs 21.8%, p = 0.60) and liver disease (12.5% vs 21.2%, p = 0.90) though neither were statistically significant. Conclusion In this retrospective chart review, RAP estimation by TTE using the guideline-recommended method had limited accuracy. Prospective evaluation with minimal time between RHC and TTE is needed to validate the accuracy of the TTE guidelines.Accuracy of TTE for RAP estimationCorrelation between RAP & TTE Variables