Comparison of Left Ventricular Outflow Tract Diameter Measurements Using Echocardiography in Newborn Infants

Abstract

Objective This study aimed to compare left ventricular outflow tract (LVOT) diameter measurements using two-dimensional (2D) echocardiography at the sino-tubular junction (STJ) and at the aortic valve (AV) hinges in newborn infants. Study Design This is a retrospective study in a tertiary neonatal unit where infants underwent echocardiography for evaluation of murmur or as part of cardiovascular assessment. Three consecutive cardiac cycles were chosen to measure the LVOT diameter in end systole at the STJ and at the AV hinges. Bias and levels of agreement were examined using Bland–Altman plot. Intraobserver variability was examined using intraclass correlation. Results A total of 366 measurements were obtained from 61 infants with a mean (standard deviation) gestation and birth weight of 33.4 (6.9) weeks and 2,181 (1369) g, respectively. There was good correlation between the LVOT diameter measurements using the STJ and AV hinges (r = 0.958, p < 0.001). The mean (standard deviation and 95% confidence interval) bias between LVOT diameter measurements using STJ and AV hinges were 0.93 (0.45 and 0.06–1.81) mm. There was good intraobserver variability between the measurements using both methods. Conclusion Using 2D echocardiography, LVOT measurements using the STJ tend to be higher when compared with LVOT measurements using the AV hinges. Key Points

Impact of Aortic Diameter Measurements at Three Anatomical Landmarks on Left Ventricular Output Calculation in Neonates

“…27 Regarding the reproducibility of LVOTD and corresponding LVO measured at AV, AS, and STJ, to the best of our knowledge, there is still conflicting evidence. 11,13 In our study, all three measurements at AV, AS, and STJ had excellent feasibility and interobserver and intraobserver reproducibility, according to the recent standards of reproducibility of echo measurements. 19 However, we consistently found that variability was lower when LVOTD was measured at the hinges of the AV, if compared to the other sites.…”

“…Interestingly, Phillips et al found a similar reproducibility of the three aortic diameters, even though they observed the lowest variability when LVOTD was measured at the AS, not at the AV 11 . However, their study had some limitations, as LVO assessment was done in stable infants and repeatability was tested only in 16 neonates.…”

“…Regarding the reproducibility of LVOTD and corresponding LVO measured at AV, AS, and STJ, to the best of our knowledge, there is still conflicting evidence 11,13 …”

“…Third, we did not investigate any association between LVO, measured at the three anatomic landmarks, and clinical outcomes. Fourth, no formal sample size calculation was done in both study cohorts, although previous studies had similar population size 10–11,13,20 . Finally, we compared LVO quantifications by echo with PCMRI only in a relatively small number of older and more stable neonates and one had a suboptimal time delay between the two measurements.…”

“…Previous studies that assessed reproducibility of LVOTD at different landmarks and compared LVOTD against a gold standard gave conflicting results. [9][10][11][12][13][14] Given that LVOTD is an essential component in LVO calculation, there is an urgent need to uniform LVOTD assessment between centers. 13 The first aim of our study was to assess the reproducibility of the LVOTD measured at three different locations (AV, AS, and STJ) and of the corresponding LVO in a cohort of very low birth weight (VLBW) neonates in the first week of life.…”