Transthoracic echocardiography: an accurate and precise method for estimating cardiac output in the critically ill patient

Abstract

BackgroundCardiac output (CO) monitoring is a valuable tool for the diagnosis and management of critically ill patients. In the critical care setting, few studies have evaluated the level of agreement between CO estimated by transthoracic echocardiography (CO-TTE) and that measured by the reference method, pulmonary artery catheter (CO-PAC). The objective of the present study was to evaluate the precision and accuracy of CO-TTE relative to CO-PAC and the ability of transthoracic echocardiography to track variations in CO, in critically ill mechanically ventilated patients.MethodsThirty-eight mechanically ventilated patients fitted with a PAC were included in a prospective observational study performed in a 16-bed university hospital ICU. CO-PAC was measured via intermittent thermodilution. Simultaneously, a second investigator used standard-view TTE to estimate CO-TTE as the product of stroke volume and the heart rate obtained during the measurement of the subaortic velocity time integral.ResultsSixty-four pairs of CO-PAC and CO-TTE measurements were compared. The two measurements were significantly correlated (r = 0.95; p < 0.0001). The median bias was 0.2 L/min, the limits of agreement (LOAs) were –1.3 and 1.8 L/min, and the percentage error was 25%. The precision was 8% for CO-PAC and 9% for CO-TTE. Twenty-six pairs of ΔCO measurements were compared. There was a significant correlation between ΔCO-PAC and ΔCO-TTE (r = 0.92; p < 0.0001). The median bias was –0.1 L/min and the LOAs were –1.3 and +1.2 L/min. With a 15% exclusion zone, the four-quadrant plot had a concordance rate of 94%. With a 0.5 L/min exclusion zone, the polar plot had a mean polar angle of 1.0° and a percentage error LOAs of –26.8 to 28.8°. The concordance rate was 100% between 30 and –30°. When using CO-TTE to detect an increase in ΔCO-PAC of more than 10%, the area under the receiving operating characteristic curve (95% CI) was 0.82 (0.62–0.94) (p < 0.001). A ΔCO-TTE of more than 8% yielded a sensitivity of 88% and specificity of 66% for detecting a ΔCO-PAC of more than 10%.ConclusionIn critically ill mechanically ventilated patients, CO-TTE is an accurate and precise method for estimating CO. Furthermore, CO-TTE can accurately track variations in CO.

Comparing Clinical Efficacy of Artificial Intelligence-powered Ultrasound with Pulse Index Continuous Cardiac Output for Monitoring Critically ill Patients

“…A recent study showed moderate consistency in hemodynamic assessment of mechanically ventilated patients with septic shock using PiCCO and CCM echocardiography [12]. The correlation between CO calculated by manual VTI and CO measured by PiCCO is about 0.95 as reported previously [13]. The corresponding correlation in the present study is 0.911, which seems to be slightly lower than that of manual determination.…”

Comprehensive in‐hospital monitoring in acute heart failure: applications for clinical practice and future directions for research. A statement from the Acute Heart Failure Committee of the Heart Failure Association (HFA) of the European Society of Cardiology (ESC)

“…However, few studies have validated the accuracy of echocardiography compared to the ‘gold standard’ pulmonary artery catheter (PAC) . One recent study in 38 mechanically ventilated patients found high correlation (r=0.95) between cardiac output measured by PAC and cardiac output measured by transthoracic echocardiography . The techniques are not interchangeable when measuring cardiac output, but they may be interchangeable to follow directional changes in cardiac output …”

“…114 One recent study in 38 mechanically ventilated patients found high correlation (r=0.95) between cardiac output measured by PAC and cardiac output measured by transthoracic echocardiography. 115 The techniques are not interchangeable when measuring cardiac output, but they may be interchangeable to follow directional changes in cardiac output. 114 Echocardiography has been strongly recommended by consensus groups in patients presenting with circulatory failure.…”

Executive summary on the use of ultrasound in the critically ill: consensus report from the 3rd Course on Acute Care Ultrasound (CACU)

“…If one divides the cardiac output by the Body Surface Area (BSA) one gets the Cardiac Index (CI). This method is very accurate and can be considered as gold standard function [36].…”