Computer modeling to improve measurement of stroke volume with echocardiography

The stroke volume (SV) can be measured by a human expert (HE) using the left ventricular outflow tract diameter (LVOTd) and its velocity time integral (VTI) with echo. If the SV is known, the cardiac output and systemic vascular resistance can be calculated. We have previously described a machine learning computer model (CM) to estimate the LVOTd. The accuracy of LVOTd^CM vs. LVOTd^HEM in estimation of the SV relative to a pulmonary artery catheter (PAC) is unknown.

Over 20 months, a prospective observational study was done in patients with a PAC placed for clinical indications. Participants underwent an echocardiogram, and at the same time the SV was measured by PAC. The SV with echo was calculated using the LVOTd^HEM and LVOTd^CM and the VTI. The bias and agreement between the metrics and PAC were determined with Bland-Altman analysis.

Computer modeling improves measurement of stroke volume with echocardiography. Eighty-four patients with a PAC were enrolled. With human expert measurement of the LVOTd and the VTI, the SV could be calculated in 59 (70%), and with the LVOTd^CM and the VTI in 78 (92%). Bland Altman analysis comparing PAC and HEM yielded a mean bias of 3.1 with 95% limits of agreement (LOA) -28.8 and 34.9. When comparing PAC and CM, bias was 1.75 and LOA of -29 and 32.5.

A machine learning model of the LVOTd allows accurate calculation of the SV using only the VTI, simplifying the assessment while increasing the yield by 22%. Machine learning tools can lower the bar for obtaining quantitative metrics with echo. Adding objective and repeatable measures will improve the ability of echo to guide therapy in the critically ill.