Quantitative Cardiac Assessment in Fetal Tetralogy of Fallot

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

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.

Aorta Dilatation in Unrepaired Tetralogy of Fallot

Background Aortic root dilation is an increasingly recognized feature in repaired tetralogy of Fallot (TOF) patients. However, the dilation at the aortic root and ascending aorta in unrepaired TOF is rarely studied. This study aims to confirm whether aortic dilation is a common feature in unrepaired TOF and investigate the factors attributed to aortic dilation. Methodology Patients with an echocardiographic diagnosis of TOF undergoing computed tomography angiography were retrospectively studied. Diameters and z scores of aortic annular (Ao1), aortic sinotubular junction (Ao2), ascending aorta (Ao3), and distal transverse aortic arch (Ao4) were measured. Preoperative body surface area (BSA), hemoglobin (Hb), hematocrit (HCT), arterial oxygen saturation (SaO2), and platelet (PLT) count were recorded. Results A total of 101 TOF patients aged 6.8 ± 9.5 years were included in this study, whose mean BSA (m2), Hb (g/L), HCT, SaO2 (%), and PLT (109/L) were 0.7 ± 0.4, 162.1 ± 3.8, 0.5 ± 0.1, 85.1 ± 9.3, and 238.1 ± 101.1, respectively. The mean z score of Ao1, Ao2, Ao3, and Ao4 were 10.3 ± 3.5, 4.7 ± 2.9, 4.0 ± 2.7, and 4.1 ± 2.4, respectively. Age and BSA were positively correlated with the z scores of Ao1 and Ao2. Preoperative Hb and HCT were positively correlated with the z scores of Ao1, Ao2, Ao3, and Ao4. Preoperative SaO2 and PLT were negatively correlated with the z scores of Ao1, Ao2, Ao3, and Ao4. Conclusions Aortic dilation is common in unrepaired TOF patients. The dilation of different levels of the aorta was correlated with age, BSA, preoperative Hb, HCT, SaO2, and PLT.

Cord blood cardiovascular biomarkers in tetralogy of fallot and D-transposition of great arteries

Previous reports suggest that cord blood biomarkers could serve as a prognostic tool for conotruncal congenital heart defects (CHD). We aimed to describe the cord blood profile of different cardiovascular biomarkers in a prospective series of fetuses with tetralogy of Fallot (ToF) and D-transposition of great arteries (D-TGA) and to explore their correlation with fetal echocardiography and perinatal outcome.

Methods

A prospective cohort study (2014-2019), including fetuses with isolated ToF and D-TGA and healthy controls, was conducted at two tertiary referral centers for CHD in Barcelona. Obstetric ultrasound and fetal echocardiography were performed in the third trimester and cord blood was obtained at delivery. Cord blood concentrations of N-terminal precursor of B-type natriuretic peptide, Troponin I, transforming growth factorβ (TGFβ), placental growth factor, and soluble fms-like tyrosine kinase-1 were determined.

Results

Thirty-four fetuses with conotruncal-CHD (22 ToF and 12 D-TGA) and 36 controls were included. ToF-fetuses showed markedly increased cord blood TGFβ (24.9 ng/ml (15.6-45.3) vs. normal heart 15.7 ng/ml (7.2-24.3) vs. D-TGA 12.6 ng/ml (8.7-37.9); P = 0.012). These results remained statistically significant even after adjusting for maternal body mass index, birth weight and mode of delivery. TGFß levels showed a negative correlation with the pulmonary valve diameter z-score at fetal echocardiography (r = -0.576, P = 0.039). No other differences were found in the rest of cord blood biomarkers among the study populations. Likewise, no other significant correlations were identified between cardiovascular biomarkers, fetal echocardiography and perinatal outcome.

Conclusions

This study newly describes increased cord blood TGFβ concentrations in ToF compared to D-TGA and normal fetuses. We also demonstrate that TGFβ levels correlate with the severity of right ventricle outflow obstruction. These novel findings open a window of research opportunities on new prognostic and potential preventive strategies.

Fetal cardiac parameters for predicting postnatal operation type of fetuses with tetralogy of Fallot

Background

To assess fetal cardiac parameters predictive of postnatal operation type in fetuses with tetralogy of Fallot (TOF).

Methods

Echocardiographic data obtained in the second and third trimesters were retrospectively reviewed for fetuses diagnosed with TOF between 2014 and 2018 at Asan Medical Center. The following fetal cardiac parameters were analyzed: 1) pulmonary valve annulus (PVA) z-score, 2) right pulmonary artery (RPA) z-score, 3) aortic valve annulus (AVA) z-score, 4) pulmonary valve peak systolic velocity (PV-PSV), 5) PVA/AVA ratio, and 6) RPA/descending aorta (DAo) ratio. These cardiac parameters were compared between a primary corrective surgery group and a palliative shunt operation followed by complete repair group.

Results

A total of 100 fetuses with TOF were included. Only one neonatal death occurred. Ninety patients underwent primary corrective surgery and 10 neonates underwent a multistage surgery. The PVA z-score, RPA z-score, and RPA/DAo ratio measured in the second trimester and the PVA z-score, RPA z-score, and PVA/AVA raio measured in the third trimester were significantly lower in the multistage surgery group, while the PV-PSV as measured in both trimesters were significantly higher in the multistage surgery group.

Conclusion

Fetal cardiac parameters are useful for predicting the operation type necessary for neonates with TOF.

Evaluation of Fetal Cardiac Size and Shape: A New Screening Tool to Identify Fetuses at Risk for Tetralogy of Fallot

OBJECTIVE

Prenatal detection rates for tetralogy of Fallot (TOF) vary between 23 and 85.7%, in part because of the absence of significant structural abnormalities of the 4-chamber view (4CV), as well as the relative difficulty in detection of abnormalities during the screening examination of the outflow tracts. The purpose of this study was to evaluate whether the 4CV and ventricles in fetuses with TOF may be characterized by abnormalities of size and shape of these structures.

METHODS

This study retrospectively evaluated 44 fetuses with the postnatal diagnosis of TOF. Measurements were made from the 4CV (end-diastolic length, width, area, global sphericity index, and cardiac axis) and the right (RV) and left (LV) ventricles (area, length, 24-segment transverse widths, sphericity index, and RV/LV ratios). Logistic regression analysis was performed to identify variables that might separate fetuses with TOF from normal controls.

RESULTS

The mean gestational age at the time of the last examination prior to delivery was 28 weeks 5 days (SD 4 weeks, 4 days). The mean z-scores were significantly lower in fetuses with TOF for the 4CV and RV and LV measurements of size and shape. Logistic regression analysis identified simple linear measurements of the 4CV, RV, and LV that had a sensitivity of 90.9 and specificity of 98.5% that outperformed the 4CV cardiac axis (sensitivity of 22.7%) as a screening tool for TOF.

CONCLUSIONS

Measurements of the 4CV, RV, and LV can be used as an adjunct to the outflow tract screening examination to identify fetuses with TOF.

Fetal Blood Flow and Genetic Mutations in Conotruncal Congenital Heart Disease

In congenital heart disease, the presence of structural defects affects blood flow in the heart and circulation. However, because the fetal circulation bypasses the lungs, fetuses with cyanotic heart defects can survive in utero but need prompt intervention to survive after birth. Tetralogy of Fallot and persistent truncus arteriosus are two of the most significant conotruncal heart defects. In both defects, blood access to the lungs is restricted or non-existent, and babies with these critical conditions need intervention right after birth. While there are known genetic mutations that lead to these critical heart defects, early perturbations in blood flow can independently lead to critical heart defects. In this paper, we start by comparing the fetal circulation with the neonatal and adult circulation, and reviewing how altered fetal blood flow can be used as a diagnostic tool to plan interventions. We then look at known factors that lead to tetralogy of Fallot and persistent truncus arteriosus: namely early perturbations in blood flow and mutations within VEGF-related pathways. The interplay between physical and genetic factors means that any one alteration can cause significant disruptions during development and underscore our need to better understand the effects of both blood flow and flow-responsive genes.

Multiscale cardiac imaging spanning the whole heart and its internal cellular architecture in a small animal model

Cardiac pumping depends on the morphological structure of the heart, but also on its subcellular (ultrastructural) architecture, which enables cardiac contraction. In cases of congenital heart defects, localized ultrastructural disruptions that increase the risk of heart failure are only starting to be discovered. This is in part due to a lack of technologies that can image the three-dimensional (3D) heart structure, to assess malformations; and its ultrastructure, to assess organelle disruptions. We present here a multiscale, correlative imaging procedure that achieves high-resolution images of the whole heart, using 3D micro-computed tomography (micro-CT); and its ultrastructure, using 3D scanning electron microscopy (SEM). In a small animal model (chicken embryo), we achieved uniform fixation and staining of the whole heart, without losing ultrastructural preservation on the same sample, enabling correlative multiscale imaging. Our approach enables multiscale studies in models of congenital heart disease and beyond.

Nomograms of Fetal Cardiac Dimensions at 18-41 Weeks of Gestation

OBJECTIVE

There is a need for standardized reference values for cardiac dimensions in prenatal life. The objective of the present study was to construct nomograms for fetal cardiac dimensions using a well-defined echocardiographic methodology in a low-risk population.

METHODS

This is a prospective cohort study including 602 low-risk singleton pregnancies undergoing a standardized fetal echocardiography to accurately assess fetal cardiac, ventricular, and atrial dimensions. Parametric regressions were tested to model each measurement against gestational age from 18 to 41 weeks of gestation.

RESULTS

Nomograms were constructed for fetal cardiac dimensions (transverse and longitudinal diameters and areas) of the whole heart, atria, and ventricles, as well as myocardial wall thicknesses. All dimensions showed a progressive increase with gestational age. The best model for most parameters was a second-degree linear polynomial. Fetal cardiac, ventricular, and atrial diameters and areas were successfully obtained in 98.6% of the fetuses, while myocardial wall thicknesses could be obtained in 96.5% of the population. The results showed excellent interobserver and intraobserver reproducibility (intraclass correlation coefficient, ICC > 0.811 and ICC > 0.957, respectively).

CONCLUSIONS

We provide standardized and comprehensively evaluated reference values for fetal cardiac morphometric parameters across gestation in a low-risk population. These no mograms would enable the early identification of different patterns of fetal cardiac remodeling.

Human fetal hearts with tetralogy of Fallot have altered fluid dynamics and forces

Studies have suggested the effect of blood flow forces in pathogenesis and progression of some congenital heart malformations. It is therefore of interest to study the fluid mechanic environment of the malformed prenatal heart, such as the tetralogy of Fallot (TOF), especially when little is known about fetal TOF. In this study, we performed patient-specific ultrasound-based flow simulations of three TOF and seven normal human fetal hearts. TOF right ventricles (RVs) had smaller end-diastolic volumes (EDVs) but similar stroke volumes (SVs), whereas TOF left ventricles (LVs) had similar EDVs but slightly increased SVs compared with normal ventricles. Simulations showed that TOF ventricles had elevated systolic intraventricular pressure gradient (IVPG) and required additional energy for ejection but IVPG elevations were considered to be mild relative to arterial pressure. TOF RVs and LVs had similar pressures because of equalization via ventricular septal defect (VSD). Furthermore, relative to normal, TOF RVs had increased diastolic wall shear stresses (WSS) but TOF LVs were not. This was caused by high tricuspid inflow that exceeded RV SV, leading to right-to-left shunting and chaotic flow with enhanced vorticity interaction with the wall to elevate WSS. Two of the three TOF RVs but none of the LVs had increased thickness. As pressure elevations were mild, we hypothesized that pressure and WSS elevation could play a role in the RV thickening, among other causative factors. Finally, the endocardium surrounding the VSD consistently experienced high WSS because of RV-to-LV flow shunt and high flow rate through the over-riding aorta. NEW & NOTEWORTHY Blood flow forces are thought to cause congenital heart malformations and influence disease progression. We performed novel investigations of intracardiac fluid mechanics of tetralogy of Fallot (TOF) human fetal hearts and found essential differences from normal hearts. The TOF right ventricle (RV) and left ventricle had similar and elevated pressure but only the TOF RV had elevated wall shear stress because of elevated tricuspid inflow, and this may contribute to the observed RV thickening. TOF hearts also expended more energy for ejection.