Patterns of Aortic Dilation in Tetralogy of Fallot: An Analysis of 100 Fetal Echocardiograms Compared With Matched Controls

Abstract

Background Although aortic dilation is common in tetralogy of Fallot (TOF), its progression and risk of dissection are not well understood. The mechanism of dilation is primarily attributed to increased flow in utero; an alternative is unequal septation of the truncus arteriosus resulting in a larger aorta and inherently hypoplastic pulmonary artery (PA). If the latter is true, we hypothesize the aorta to PA ratio in TOF is stable throughout gestation, and sums of great artery dimensions are similar to controls. Methods and Results We performed a single‐center retrospective study of fetuses with TOF (2014–2020) and matched controls. We compared sums of diameters, circumferences, and cross‐sectional areas of the aorta and PA and evaluated the aorta to PA ratio across gestation in 2 TOF subtypes: pulmonary stenosis and atresia (TOF‐PA). There were 100 echocardiograms with TOF (36% TOF‐PA) with median gestational age of 31 weeks (interquartile range 26.5–34.4) and median maternal age of 34 years (interquartile range 30–37). There were no differences in sums of great artery dimensions between TOF‐pulmonary stenosis and controls. In TOF‐PA, sums were significantly lower than controls ( P values <0.01). The aorta to PA ratio was stable throughout gestation (Pearson's r =0.08 [95% CI, −0.12 to 0.27], −0.06 [95% CI, −0.25 to 0.14]). Conclusions The aorta in fetal TOF is large but grows proportionally throughout gestation, with sums of great artery dimensions similar to controls. TOF‐PA appears distinct from TOF‐pulmonary stenosis (with smaller sums), warranting further investigation. In conclusion, our findings suggest an intrinsic developmental mechanism contributes to aortic dilation in TOF.

Evaluating fetal pulmonary vascular development in congenital heart disease: a comparative study using the McGoon index and multiple parameters of fetal echocardiography

“…Conversely, the study of 21 fetuses with reduced or detached aortic ow in Group C revealed signi cantly greater values for MGI, PA-Zs, and PA/AO ratios than those in the other two groups. These ndings, in conjunction with previous studies on CHD fetuses [9][10][11], suggest that fetal MGI serves as a valuable indicator for evaluating PA development during the prenatal period, which has great implications for the dynamic evaluation of cardiovascular development in advanced intrauterine CHD fetuses, guiding disease analysis and prognosis, and providing reasonable information for prenatal consultations. Subgroup analysis in Group B indicated that fetuses with backward DA ow had smaller values for PA, PA-Zs, LPA + RPA, and MGI than the forward DA perfusion group.…”

“…However, two deaths occurred due to TOF (MGI 1.20) and hypoplastic right heart syndrome (HRHS). This suggests that the cardiovascular structure and functional status of fetuses with severe PS can vary signi cantly postnatally, necessitating individualized treatment strategies based on each child's PA development [9]. Despite the overall better prognosis in isolated PS, MGI may still decrease.…”

“…Z-score: Z-scores were calculated following statistical analysis methods outlined by Royston and Wright [8], leveraging regression equations established by previous studies within the study group [9][10][11]: AO Predicted values mean = 0.101 × FL − 0.012, PA Predicted values mean = 0.114 × FL + 0.028, AO Predicted SD = 0.005919 × FL + 0.016, and PA Predicted SD = 0.0113 × FL + 0.0122. Z-scores were computed using the equations: AO Z-score = (Actually measured AO − Predicted AO according to FL) / Predicted SD of AO; PA-Zs = (Actually measured PA − Predicted PA according to FL) / Predicted SD of PA.…”

Assessment of Pulmonary Arterial Vascular Impedance in Fetuses With Tetralogy of Fallot

“…Vascular remodeling occurred in the middle membrane of the pulmonary trunk in fetuses with TOF due to decreased blood flow, resulting in thin and sparse elastic fibers and increased content of collagen fibers and matrix. 7,8 Moreover, suppression of nitric oxide (NO) and prostaglandin-I-2 (PGI 2 ) actions as a result of low pulmonary blood flow in fetuses with TOF leads to vasoconstriction, which is closely related to the maintenance of high vascular impedance in the fetal lung. The imbalance between PGI 2 and thromboxane A2 causes local platelet aggregation, which may stimulate the migration and division of endomyocytes, resulting in histological changes in the MPA.…”