Relationship between interatrial communication, ductus arteriosus, and pulmonary flow patterns in fetuses with transposition of the great arteries: prediction of neonatal desaturation

Balloon Atrial Septostomy: Does the Balloon Size Matter?

Background

Dextro-transposition of the great arteries is a congenital heart defect with eventually lethal life-threatening consequences of hypoxic low cardiac output. When a balloon atrial septostomy (BAS) is needed, it is performed shortly after birth to create an interatrial shunt and improve systemic blood oxygenation and haemodynamic conditions. In 2019 and 2020, the withdrawal of some balloon atrioseptostomy catheters from the market led to increased use of catheters with different materials, shapes, and sizes. The main objective of this study was to investigate whether the size of the Miller and Fogarty balloon (Edwards Lifesciences) in its 2 variations, the 4.0 cc and the 1.8 cc, had a different impact on the systemic oxygen saturation, on the atrial septal defect (ASD) size, or on the type and frequency of procedure-related complications.

Methods

We conducted a retrospective study on 134 consecutive patients diagnosed with dextrotransposition of the great arteries between 2002 and 2018 who underwent BAS in a tertiary paediatric hospital in Canada.

Results

BAS resulted in a significant increase in oxygen saturation of 18.91% ± 12.95% points (P < 0.0001) and a significant increase in the resulting ASD by 3.92 ± 1.58 mm (P < 0.0001). There was no significant difference in resulting oxygen saturation (P = 0.8370) or the final ASD size (P = 0.2193) based on the balloon size. Severe or life-threatening complications were rare (1%) with no subsequent patient demise.

Conclusions

This is the first study to show that the small balloon is as efficient as the large balloon catheter including in premature patients. This raises the question whether different balloon sizes are necessary.

Modern advances regarding interatrial communication in congenital heart defects

BACKGROUND

The interatrial communication, one of the most frequent congenital heart defects, represents an important intracardiac shunt between systemic and pulmonary circulations. Direction and magnitude of the interatrial shunting depends upon several features, including defect size, shape and location, pressure difference between right and left atrium, and difference in right and left ventricular compliance.

METHODS

In this review article, the presence or absence of interatrial communication, and its role, have been analyzed, as they can have a critical impact on the cardiovascular physiopathology, and the interatrial communication can prove to be either clinically harmful, useful or indispensable. Accordingly, the utility and role of the interatrial communication in modern congenital, pediatric and adult, disease has evolved, with modification of the indications to close, maintain patency, or create an interatrial communication.

RESULTS

The interatrial communication and shunting can be manipulated to maximize the oxygen delivery to the tissues, accordingly with the underlying congenital heart defect. While not always relevant to patients with bi-ventricular circulations, this becomes extremely important in children and adults with complex congenital heart defects.

CONCLUSIONS

With improving long-term survival for the vast majority of congenital heart patients, an advanced understanding of the role and utility of the interatrial communication, and of all the possibilities of its manipulation, is essential to improve the patient outcomes.

Impact of ductus arteriosus constriction and restrictive foramen ovale on global hemodynamics for term fetuses with d-TGA

The ductus arteriosus (DA) constriction and restrictive foramen ovale (FO) are known as the leading cause of compromise and death of fetuses with dextro-transposition of the great arteries (d-TGA). Although the d-TGA fetal hemodynamics is of great importance in making diagnosis and management of the congenital heart defect, it remains poorly understood, particularly in terms of abnormal DA and FO. In this study, we developed a closed-loop 0-1D multiscale model of the fetal cardiovascular system (CVS) specified for the d-TGA circulation and conducted a systematic study of the impact of the DA constriction and restrictive FO on fetal hemodynamics. We found that the DA constriction led to a pronounced increase in the pulmonary artery pressure, pulmonary and mitral valve (PV and MV) regurgitation as well as left heart volume; the restrictive FO was responsible for reducing MV E/A ratio, ie, the ratio of peak early filling and late diastolic filling velocities, and PV peak systolic flow (PSV) but could increase both aortic valve (AV) PSV and aortic isthmus systolic index (ISI). Moreover, the amount of blood flowing through the DA was observed equivalent to that through the FO; the influence of DA constriction on the cerebral and placental perfusions are larger than that of the FO. Our results demonstrate that the proposed fetal cardiovascular model may be a useful tool for studying the underlying mechanisms associated with d-TGA fetal circulation and providing insights into its complex physiology and pathology.

Urgent neonatal balloon atrial septostomy in simple transposition of the great arteries: predictive value of fetal cardiac parameters

OBJECTIVES

To investigate the impact of abnormal perinatal loading conditions on cardiac geometry and function in term fetuses and neonates with transposition of the great arteries with intact interventricular septum (simple TGA), and to explore the predictive value of fetal cardiac parameters for an urgent balloon atrial septostomy (BAS) after birth.

METHODS

This was a prospective longitudinal follow-up study of women delivering at term, including both uncomplicated pregnancies with normal outcome and pregnancies affected by fetal simple TGA. Conventional, spectral-tissue Doppler and speckle-tracking echocardiographic parameters were obtained within 1 week before delivery and within the first few hours after delivery. Neonates with simple TGA that required urgent BAS were assessed after the procedure and before corrective arterial switch surgery. Cardiac parameters were normalized by cardiac cycle length, ventricular end-diastolic length or end-diastolic dimension, as appropriate. Fetal and neonatal cardiac parameters were compared between simple-TGA cases and controls, and perinatal changes in the simple-TGA group were assessed. Receiver-operating-characteristics (ROC)-curve analysis was used to assess the predictive value of fetal cardiac parameters for urgent BAS after birth in the simple-TGA group.

RESULTS

A total of 67 pregnant women delivering at term were included in the study (54 normal pregnancies and 13 with a diagnosis of fetal simple TGA). Compared with normal term fetuses, term fetuses with simple TGA exhibited more globular hypertrophied ventricles, increased biventricular systolic function and diastolic dysfunction (right ventricular (RV) sphericity index (SI), 0.58 vs 0.54; left ventricular (LV)-SI, 0.55 vs 0.49; combined cardiac output (CCO), 483 vs 406 mL/min/kg; LV torsion, 4.3 vs 3.0 deg/cm; RV isovolumetric relaxation time (IVRT'), 127 vs 102 ms; P < 0.01 for all). Compared with normal neonates, neonates with simple TGA demonstrated biventricular hypertrophy, a more spherical right ventricle and altered systolic and diastolic functional parameters (RV-SI, 0.61 vs 0.43; RV myocardial performance index, 0.47 vs 0.34; CCO, 697 vs 486 mL/min/kg; LV-IVRT', 100 vs 79 ms; RV-IVRT', 106 vs 71 ms; P < 0.001 for all). Paired comparison of neonatal and fetal cardiac indices in the simple-TGA group showed persistence of the fetal phenotype, increased biventricular systolic myocardial contractility and CCO, and diastolic dysfunction (RV systolic myocardial velocity (S'), 0.31 vs 0.24 cm/s; LV-S', 0.23 vs 0.18 cm/s; CCO, 697 vs 483 mL/min/kg; LV torsion, 1.1 vs 4.3 deg/cm; P < 0.001 for all). Several fetal cardiac parameters in term fetuses with simple TGA demonstrated high predictive value for an urgent BAS procedure after birth. Our proposed novel fetal cardiac index, LV rotation-to-shortening ratio, as a potential marker of subendocardial dysfunction, for a cut-off value of ≥ 0.23, had an area under the ROC curve (AUC) of 0.94, sensitivity of 100% and specificity of 83%. For RV/LV end-diastolic area ratio ≥ 1.33, pulmonary-valve-to-aortic-valve-dimension ratio ≤ 0.89, RV/LV cardiac output ratio ≥ 1.38 and foramen-ovale-dimension-to-total-interatrial-septal-length ratio ≤ 0.27, AUC was 0.93-0.98, sensitivity was 86% and specificity was 83-100% for all.

CONCLUSIONS

Simple-TGA fetuses exhibited cardiac remodeling at term with more profound alterations in these cardiac parameters after birth, suggestive of adaptation to abnormal loading conditions and possible adaptive responses to hypoxemia. Perinatal adaptation in simple TGA might reflect persistence of the abnormal parallel arrangement of cardiovascular circulation and the presence of widely patent fetal shunts imposing volume load on the neonatal heart. The fetal cardiac parameters that showed high predictive value for urgent BAS after birth might reflect the impact of late-gestation pathophysiology and progressive hypoxemia on fetal cardiac geometry and function in simple TGA. If these findings are validated in larger prospective studies, detailed cardiac assessment of fetuses with simple TGA near term could facilitate improvements in perinatal management and refinement of the timing of postnatal intervention strategies to prevent adverse pregnancy outcomes. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Cardiac hemodynamics in fetuses with transposition of the great arteries and intact ventricular septum from diagnosis to end of pregnancy: longitudinal follow-up

OBJECTIVES

Little is known about cardiac hemodynamics in the fetus with transposition of the great arteries and intact ventricular septum (TGA-IVS). Better understanding of the fetal physiology in TGA-IVS would help to provide insights into specific clinical complications observed after birth, in particular neonatal hypoxia and pulmonary hypertension. The aim of this study was to assess cardiac hemodynamics in fetuses with TGA-IVS by performing systematic longitudinal echocardiographic follow-up from diagnosis to delivery.

METHODS

This was a longitudinal retrospective study of fetuses referred between 2010 and 2018 to the Sainte-Justine University Hospital Centre. Complete assessment of cardiac hemodynamics was performed in fetuses with TGA-IVS at 18-22, 28-32 and 35-38 weeks' gestation, which were compared with normal fetuses matched for gestational age. The maximum diameter of the foramen ovale was measured using two-dimensional echocardiography under the guidance of color Doppler echocardiography. Fetal cardiac hemodynamics were analyzed according to postnatal preductal transcutaneous oxygen saturation (TcSO₂ ) < 65% or ≥ 65%, as a neonatal outcome, in fetuses with TGA-IVS.

RESULTS

In total, 59 fetuses with TGA-IVS and 160 normal fetuses were included. Global cardiac output was significantly higher in fetuses with TGA-IVS than in controls, mainly owing to higher global pulmonary output, while global systemic cardiac output did not differ between TGA-IVS fetuses and controls throughout pregnancy. Aortic flow (right ventricular output in fetuses with TGA-IVS, left ventricular output in controls) was significantly higher in fetuses with TGA-IVS than in normal fetuses. Ductal flow was significantly lower in fetuses with TGA-IVS at every timepoint, and this difference increased considerably after 28-32 weeks. In parallel, the diameter of the foramen ovale was significantly smaller in fetuses with TGA-IVS at 28-32 and 35-38 weeks, with a stagnation in growth after 28 weeks, compared with continuous growth in normal fetuses. Most of these cardiac hemodynamic anomalies in fetuses with TGA-IVS were already present at 18-22 weeks, and the differences became greater at 28-32 weeks' gestation. TGA-IVS neonates with TcSO₂ < 65% had lower fetal left ventricular output, higher diastolic ductal retrograde flow and smaller foramen ovale at 28-32 weeks, compared with fetal values in those with postnatal TcSO₂ ≥ 65%.

CONCLUSIONS

Compared with normal fetuses, those with TGA-IVS undergo a complex redistribution of blood flow during the second half of pregnancy, with higher global pulmonary flow, lower ductal flow (with negative diastolic flow at the end of pregnancy) and a smaller foramen ovale. In addition, fetal cardiac hemodynamic anomalies observed at 28-32 weeks' gestation were associated with lower postnatal TcSO₂ . These observations may provide a better understanding of premature closure of the foramen ovale and postnatal hypoxia that are specific to TGA-IVS physiology. © 2019 International Society of Ultrasound in Obstetrics and Gynecology.

Comprehensive Functional Echocardiographic Assessment of Transposition of the Great Arteries: From Fetus to Newborn

To improve the understanding of the pathophysiology of transposition of the great arteries with intact ventricular septum (TGA/IVS) and the cardiac remodeling occurring from fetal to neonatal life, we performed a morphometric and functional echocardiographic assessment in fetuses and newborns. This was a prospective case-control study performed in a tertiary referral center, which included fetuses and newborns with a diagnosis of TGA/IVS between 2011 and 2018. Morphometry and systolic and diastolic function parameters were compared with age and body surface-matched healthy controls. Twenty-one TGA/IVS patients were included during the study period and morphometric and functional echocardiographic data were recorded. TGA/IVS patients showed morphometric and functional changes of increased overall volume and output, predominantly in the aortic component from fetus to newborn, probably due to compensatory mechanisms secondary to brain hypoxia.

Fetal dynamic phase-contrast MR angiography using ultrasound gating and comparison with Doppler ultrasound measurements

OBJECTIVES

To investigate the feasibility of fetal phase-contrast (PC)-MR angiography of the descending aorta (AoD) using an MR-compatible Doppler ultrasound sensor (DUS) for fetal cardiac gating and to compare velocimetry with Doppler ultrasound measurements.

METHODS

In this prospective study, 2D PC-MR angiography was performed in 12 human fetuses (mean gestational age 32.8 weeks) using an MR-compatible DUS for gating of the fetal heart at 1.5 T. Peak flow velocities in the fetal AoD were compared with Doppler ultrasound measurements performed on the same day. Reproducibility of PC-MR measurements was tested by repeated PC-MR in five fetuses.

RESULTS

Dynamic PC-MR angiography in the AoD was successfully performed in all fetuses using the DUS, with an average fetal heart rate of 140 bpm (range 129-163). Time-velocity curves revealed typical arterial blood flow patterns. PC-MR mean flow velocity and mean flux were 21.2 cm/s (range 8.6-36.8) and 8.4 ml/s (range 3.2-14.6), respectively. A positive association between PC-MR mean flux and stroke volume with gestational age was obtained (r = 0.66, p = 0.02 and r = 0.63, p = 0.03). PC-MR and Doppler ultrasound peak velocities revealed a highly significant correlation (r = 0.8, p < 0.002). Peak velocities were lower for PC-MR with 69.1 cm/s (range 39-125) compared with 96.7 cm/s (range 60-142) for Doppler ultrasound (p < 0.001). Reproducibility of PC-MR was high (p > 0.05).

CONCLUSION

The MR-compatible DUS for fetal cardiac gating allows for PC-MR angiography in the fetal AoD. Comparison with Doppler ultrasound revealed a highly significant correlation of peak velocities with underestimation of PC-MR velocities. This new technique for direct fetal cardiac gating indicates the potential of PC-MR angiography for assessing fetal hemodynamics.

KEY POINTS

• The developed MR-compatible Doppler ultrasound sensor allows direct fetal cardiac gating and can be used for prenatal dynamic cardiovascular MRI. • The MR-compatible Doppler ultrasound sensor was successfully applied to perform intrauterine phase-contrast MR angiography of the fetal aorta, which revealed a highly significant correlation with Doppler ultrasound measurements. • As fetal flow hemodynamics is an important parameter in the diagnosis and management of fetal pathologies, fetal phase-contrast MR angiography may offer an alternative imaging method in addition to Doppler ultrasound and develop as a second line tool in the evaluation of fetal flow hemodynamics.

Ductus arteriosus and fetal echocardiography: Implications for practice

The ductus arteriosus (DA) is a crucial part of the fetal circulation, both in the normal fetus and in critical congenital heart disease (CHD). It allows shunting between the pulmonary and systemic circulations. In physiological prenatal conditions, the DA lets the majority of right ventricular output bypass the fluid-filled, high-resistance lungs. The DA can cause hemodynamic compromise in the fetus and neonate when constricted or absent (in isolation or in patients with CHD) and may lead to pre- or postnatal sequelae within other systems when forming part of a vascular ring. In CHD, the DA can be interrogated by fetal echocardiography to infer information regarding severity of pulmonary outflow tract obstruction, adequacy of the sub-pulmonary ventricle to supply pulmonary blood flow, and to predict the likelihood of atrial septum restriction in transposition of the great arteries. A good understanding of the DA is crucial for fetal cardiologists.