Possible usefulness of echocardiographic Z-scores in autopsy routine of the foetal great vessels

Abstract

Background: Abnormal diameters of foetal vessels are common findings in congenital heart defects. However, it is difficult for pathologist to assess whether the diameters of the vessels are normal or not and to compare with echocardiographic data. The Z-score is a dimensionless quantity representing the distance between the raw score and population mean in standard deviation units. Using Z-score, we can compare single cases to average standards in the population.
Aim: To compare diameters of great arteries measured in specimens fixed in 10% formalin solution to normal values obtained on echocardiography using Z-scores.
Material and methods: The study was performed on 43 formalin-fixed normal foetal hearts aged from 19 to 40 weeks of gestation. Each specimen was dissected and the following diameters were measured: aortic valve (AoV), ascending aorta (AAo), descending aorta (DAo), aortic isthmus (AoI), ductus arteriosus (DA), pulmonary trunk valve (PV), and pulmonary arteries (RPA and LPA). Z-score parameters were calculated for all structures using the Foetal Echo Z-score Calculator.
Results: Z-score values of all measured foetuses were mostly found to fit within the echocardiographic norms, although the most reliable results were obtained for foetuses aged 23 weeks. This group was represented by the highest number of specimens. The minimal and maximal Z-score values were, respectively: AoV –3.45, 1.4; AAo –4.24, –0.11; DAo –2.12, 1.29; PV –3.21, 0.69; RPA –3.4, 0.84; LPA –2.25, 0.31; AoI –1.97, 0.96; DA –3.56, –1.52.
Conclusions: The diameters of great arteries measured on autopsy are comparable to the results obtained from echocardiographic measurement. Z-score values for foetal echocardiography can be applied to post-mortem examination.