Automated echocardiography for measuring and tracking cardiac output after cardiac surgery: a validation study


Echocardiographic measurement of cardiac output with automated software analyses of spectral curves in the left ventricular outflow tract has been introduced. This study aimed to assess the precision and accuracy of cardiac output measurements as well as the ability to track cardiac output changes over time comparing the automated echocardiographic method with the continuous pulmonary artery thermodilution cardiac output technique and the manual echocardiographic method in cardiac surgery patients. Cardiac output was measured simultaneously with all three methods in 50 patients on the morning after cardiac surgery. A second comparison was performed 90–180 min later. Precisions for each method were measured. Bias and limits of agreement (LoA) between methods were assessed and concordance- and polar plots were used for evaluating trending of cardiac output. When comparing the automated echocardiographic method with the thermodilution technique, the mean bias was 0.72 L/min with LoA − 1.89; 3.33 L/min corresponding to a percentage error of 46%. The concordance rate was 47%. The mean bias between the automated- and the manual echocardiographic methods was − 0.06 L/min (95% LoA − 2.33; 2.21 L/min, percentage error 42%). The concordance rate was 79%. The automated echocardiographic method did not meet the criteria for interchangeability with the thermodilution technique or the manual echocardiographic method. Trending ability was poor when compared to the continuous thermodilution technique, but moderate when compared to the manual echocardiographic method.

Trial registry number: NCT03372863. Retrospectively registered December 14th 2017.

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Fig. 1
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Continuous cardiac output


Confidence interval


Cardiac output


Coefficient of variation


Limits of agreement


Left ventricular outflow tract


Pulmonary artery catheter


Region of interest


Velocity time integral


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The authors wish to thank the staff at the postoperative intensive care unit, Aarhus University Hospital, for their invaluable assistance in patient inclusion and execution of the protocol. Likewise, the authors thank GE Healthcare for making available a Venue R1 ultrasound system for the study.



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Correspondence to Peter Juhl-Olsen.

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Conflict of interests

Peter Juhl-Olsen has received minor funds from GE Healthcare and Novartis for teaching courses on critical care. GE Healthcare provided the Venue R1 ultrasound system free of charge for the study without influence on study design, study execution, data interpretation or any aspect of the manuscript writing. All other authors declare that they have not conflict of interests.

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Polar plots for comparison of the automated software echocardiographic method (automated CO), the manual echocardiographic method (manual CO) and continuous cardiac output (CCO) for measuring cardiac output (CO). Individual comparisons are given and both standard and modified polar plots are presented. Standard polar plots include data outside a 10% central exclusion zone of the polar plots as proposed [19]. Modified polar plots reuses the 15% central exclusion zone of the four-quadrant plots. Biases (red lines) and limits of agreement (black lines) for the polar lot are given in the manuscript. The first scan was performed on the morning after surgery. The second scan was performed one to 3 h later following routine physiotherapy and mobilisation. Supplementary material 1 (TIFF 699 kb)

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Juhl-Olsen, P., Smith, S.H., Grejs, A.M. et al. Automated echocardiography for measuring and tracking cardiac output after cardiac surgery: a validation study. J Clin Monit Comput 34, 913–922 (2020).

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  • Cardiac output
  • Echocardiography
  • Ultrasonography
  • Thoracic surgery
  • Haemodynamics