A novel method of calculating stroke volume using point-of-care echocardiography

Abstract

Background: Point-of-care transthoracic echocardiography (POC-TTE) is essential in shock management, allowing for stroke volume (SV) and cardiac output (CO) estimation using left ventricular outflow tract diameter (LVOTD) and left ventricular velocity time integral (VTI). Since LVOTD is difficult to obtain and error-prone, the body surface area (BSA) or a modified BSA (mBSA) is sometimes used as a surrogate (LVOTD BSA , LVOTD mBSA). Currently, no models of LVOTD based on patient characteristics exist nor have BSA-based alternatives been validated. Methods: Focused rapid echocardiographic evaluations (FREEs) performed in intensive care unit patients over a 3year period were reviewed. The age, sex, height, and weight were recorded. Human expert measurement of LVOTD (LVOTD HEM) was performed. An epsilon-support vector regression was used to derive a computer model of the predicted LVOTD (LVOTD CM). Training, testing, and validation were completed. Pearson coefficient and Bland-Altman were used to assess correlation and agreement. Results: Two hundred eighty-seven TTEs with ideal images of the LVOT were identified. LVOTD CM was the best method of SV measurement, with a correlation of 0.87. LVOTD mBSA and LVOTD BSA had correlations of 0.71 and 0.49 respectively. Root mean square error for LVOTD CM , LVOTD mBSA , and LVOTD BSA respectively were 13.3, 37.0, and 26.4. Bland-Altman for LVOTD CM demonstrated a bias of 5.2. LVOTD CM model was used in a separate validation set of 116 ideal images yielding a linear correlation of 0.83 between SV HEM and SV CM. Bland Altman analysis for SV CM had a bias of 2.3 with limits of agreement (LOAs) of − 24 and 29, a percent error (PE) of 34% and a root mean square error (RMSE) of 13.9. Conclusions: A computer model may allow for SV and CO measurement when the LVOTD cannot be assessed. Further study is needed to assess the accuracy of the model in various patient populations and in comparison to the gold standard pulmonary artery catheter. The LVOTD CM is more accurate with less error compared to BSA-based methods, however there is still a percentage error of 33%. BSA should not be used as a surrogate measure of LVOTD. Once validated and improved this model may improve feasibility and allow hemodynamic monitoring via POC-TTE once it is validated.

The POCUS Consult: How Point of Care Ultrasound Helps Guide Medical Decision Making

“…10,56 The use of these techniques requires precise measurements to avoid errors in calculation and subsequent management. 44,56 Computer-derived models for stroke volume calculation may offer an alternative when accurate measurements cannot be obtained, 57 but more studies are needed to evaluate this practice. There are limitations associated with the use of these approaches.…”

Pulmonary Congestion Due to Right and Left Heart Output Mismatching: A Case Report and Literature Review

“…Consequently, we began to consider another type of pulmonary congestion because we found mismatching of the right and left heart stroke volume (Table 1). Through echo measurements and calculation, we can get the left ventricle output according to the formula VTI × π × (1/2D LVOT ) 2 (Tan et al, 2017;Aligholizadeh et al, 2020). D LVOT was 0.97 cm and VTI was 5.38 cm.…”

Arterial Diameter Variations as a New Index for Stroke Volume Assessment: An Experimental Study on a Controlled Hemorrhagic Shock Model in Piglets

“…The subaortic velocity-time index (aoVTI) is a pulsed-wave Doppler index measured in transthoracic echography 5 . The aoVTI measured at the left ventricular outflow tract provides a good estimation of SV 6–8 . However, aoVTI measurement remains difficult in critical conditions, principally because of technical difficulties and elevated heart rates (HRs) 9,10 .…”

“…5 The aoVTI measured at the left ventricular outflow tract provides a good estimation of SV. [6][7][8] However, aoVTI measurement remains difficult in critical conditions, principally because of technical difficulties and elevated heart rates (HRs). 9,10 Speckle tracking is an ultrasonographic technique providing acoustic marker monitoring, which has already been studied in emergency department settings for myocardial motion and pleural sliding analysis.…”