Evaluation of the post‐LA space index in the normal fetus

Abstract

Objective We previously reported the post‐LA space index (PLAS index), which is calculated as left atrial‐descending aorta distance (LD) divided by the diameter of descending aorta (DA), could be useful for prenatal diagnosis of total anomalous pulmonary venous connection (TAPVC). In this study, we evaluated PLAS index in normal fetuses to assess its usefulness. Methods In 304 normal fetuses, LD and DA were retrospectively measured, and the PLAS index was calculated. In 206 fetuses with data on the biparietal diameter (BPD) and femoral length (FL), the relationship between the PLAS index and them was investigated. We also calculated the PLAS index in 13 TAPVC fetuses. Results Mean LD was 3.0+/−0.94 mm, mean DA was 4.8+/−0.87 mm, and the mean PLAS index was 0.62+/−0.19. DA and LD were correlated with gestational age (R = 0.52, 0.25), while the PLAS index showed little variation with gestational age (R < 0.2). BPD and FL were correlated with DA (R = 0.4, 0.42) but not with LD or the PLAS index (both R < 0.2). In the TAPVC fetuses, both LD and the PLAS index were significantly higher than in normal fetuses. Conclusion In normal fetuses, the PLAS index was independent of gestational age and fetal physique and may be useful for raising the suspicion of congenital heart disease, including TAPVC.

Post–Left Atrium Space Index in Fetuses With Total Anomalous Pulmonary Venous Connection and Other Congenital Heart Diseases

“…7 In their following study, they found that the optimal cutoff value of the PLAS index was 1.17, with the sensitivity and specificity both being 100%. 4 They suggested that if the cutoff value is set at 1.0, the sensitivity would be 100% in both studies, with specificity of 89% and 93%, respectively. This suggests that determining whether the distance behind the LA is wider than the DA may be a simple method for detecting cardiac abnormalities.…”

“…Some studies have reported changes in the PLAS in fetal CHDs, especially for the prenatal diagnosis of a TAPVC. 4,5,7,12 Valsangiacomo et al 12 reported that a separation between the posterior wall of the atrium and the descending aorta was observed in fetuses with TAPVC. Berg et al 5 suggested that an abnormality in the area behind the heart on fetal echocardiography is an important clue when screening for fetal CHDs, including TAPVC.…”

“…The PLAS index is a useful parameter for the prediction of TAPVC. Kawazu et al 4,7 reported that a cutoff value of 1.27 for the PLAS index was optimal for distinguishing between TAPVC and normal, with sensitivity of 100% and specificity of 99%. 7 In their following study, they found that the optimal cutoff value of the PLAS index was 1.17, with the sensitivity and specificity both being 100%.…”

“…Thus, the specificity was higher than that of previous reports, and the sensitivity was consistent with that in previous reports. 4,7 However, previous studies only compared an isolated TAPVC group with a control group with a completely normal intracardiac structure, without considering the influence of intracardiac anomalies on the PLAS index.…”

“…3 Some studies have suggested that the post-left atrium space (PLAS) index can be used as an effective index for the diagnosis of TAPVC. [4][5][6][7] Notably, previous studies have not explored whether other types of congenital heart defects have an impact on the PLAS index. We hypothesized that intracardiac anomalies may have an effect on the PLAS index, and the PLAS indices of different types of isolated TAPVC may be different.…”