228 - Effect of Different Location of Doppler Sampling Gate at the Ventricular Outflow Tract on the Velocity Time Integral When Measuring Cardiac Output in Neonates

Poster Number: 228
Publication Number: 228.33

Jane Huang, University of Southern California/Keck School of Medicine of USC, MONTCLAIR, CA, United States; Mahmood ebrahimi, LAC+USC Medical Center, Encin, CA, United States; Manuel Durand, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States; Shahab Noori, Children's Hospital Los Angeles, Los Angeles, CA, United States; Rangasamy Ramanathan, Keck School of Medicine of USC, Los Angeles, CA, United States; Rowena Cayabyab, University of Southern California/LAC+USC Medical Center, Los Angeles, CA, United States; mohammad Amin. Adie, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States

Background: Cardiac output (CO) is an objective measurement to assess the hemodynamic status in neonates. CO is the product of stroke volume (SV) and heart rate. SV can be estimated using transthoracic echocardiogram by obtaining ventricular outflow cross-sectional area (CSA) and velocity time integral (VTI). The American Society of Echocardiography recommended Doppler gate sampling location for VTI to be below the valve just at the level of both ventricular outflow tracts (VOT). However, there is inconsistency in method of acquiring VTI among care providers. The effect of different methodology, especially the locations of the Doppler sampling gate at the outflow tract on VTI is not known.

Objective: The objective of this quality improvement study is to assess the effect of different Doppler sampling gate locations at the ventricular outflow (below, at the hinges, or the tip of the valve) on the VTI and CO in neonates.

Design/Methods: Healthy term neonates born between February to May 2022 without any congenital heart disease were included in this project. All echocardiograms were performed by a single echocardiographer. Collected echocardiographic data included shortening fraction, diameter of right and left VOT at the hinges of the aortic and pulmonic valves, VTI of both ventricles outflow tracts obtained at 1 mm below the valve, at the hinges of the valve and at the tip of the valve, and size of patent ductus arteriosus (PDA) and patent foramen ovale (PFO). ANOVA with Bonferroni correction were used to determine the differences between the VTI and CO sampled at the three locations of the VOT.

Results: 41 neonates with median gestational age of 38.6 weeks and mean birth weight of 3155 grams had echocardiograms obtained at a median of 23 hours of life. 24/41 infants (59%) had PDA and 39/41 (95%) had PFO. VTI and CO were significantly different at the 3 locations of both VOT (Table). There was an average increase in left CO of 29 ml/kg/min versus 65 ml/kg/min in right CO every time the Doppler sampling gate was moved up the outflow tract from below the valve to hinges of the valve and then to the tip of the valve.

Conclusion(s): There is significant difference in measurements of VTI and CO depending on location of Doppler gate sampling at the outflow tract. Consistency in the Doppler gate location when measuring VTI and CO is essential in assessing hemodynamic status. Changes in CO may be related to the location of Doppler gate sampling, rather than changes in hemodynamic status in critically ill newborns.