Current concepts in fetal cardiovascular disease

3-D volumetric MRI evaluation of the placenta in fetuses with complex congenital heart disease

INTRODUCTION

Placental insufficiency remains a common cause of perinatal mortality and neurodevelopmental morbidity. Congenital heart disease (CHD) in the fetus and its relationship to placental function is unknown. This study explores placental health and its relationship to neonatal outcomes by comparing placental volumes in healthy pregnancies and pregnancies complicated by CHD using in vivo three-dimensional MRI studies.

METHODS

In a prospective observational study, pregnant women greater than 18 weeks gestation with normal pregnancies or pregnancies complicated by CHD were recruited and underwent fetal MR imaging. The placenta was manually outlined and the volume was calculated in cm(3). Brain volume was also calculated and clinical data were also collected. Relationships, including interactive effects, between placental and fetal growth, including brain growth, were evaluated using longitudinal multiple linear regression analysis.

RESULTS

135 women underwent fetal MRI between 18 and 39 weeks gestation (mean 31.6 ± 4.4). Placental volume increased exponentially with gestational age (p = 0.041). Placental volume was positively associated with birth weight (p < 0.001) and increased more steeply with birth weight in CHD-affected fetuses (p = 0.046). Total brain and cerebral volumes were smaller in the CHD group (p < 0.001), but brainstem volume (p < 0.001) was larger. Placental volumes were not associated with brain volumes.

DISCUSSION

Impaired placental growth in CHD is associated with gestational age and birth weight at delivery. Abnormalities in placental development may contribute to the significant morbidity in this high-risk population. Assessment of placental volume by MRI allows for in vivo assessments of placental development.

Antihypertensive medication use during pregnancy and the risk of cardiovascular malformations

We used data from the National Birth Defects Prevention Study, a population-based, case-control study, to examine whether previously reported associations between antihypertensive medications and cardiovascular malformations could be confirmed and to explore whether new associations might be identified. Cases (n=5021) were ascertained through birth defects surveillance systems from 1997 through 2003 in 10 US states. Controls (n=4796) were live births without birth defects selected randomly from birth certificates or hospital discharge listings in the same geographic regions. Logistic regression was used to examine the relationship between antihypertensive medication treatment and the occurrence of cardiovascular malformations while controlling for confounding variables. First-trimester treatment with antihypertensive medication was associated with pulmonary valve stenosis (odds ratio [OR]: 2.6; 95% CI: 1.3 to 5.4), Ebstein malformation (crude OR: 11.4; exact 95% CI: 2.8 to 34.1), coarctation of the aorta (OR: 3.0; 95% CI: 1.3 to 6.6), and secundum atrial septal defects (OR: 2.4; 95% CI: 1.3 to 4.4). Treatment initiated after the first trimester was associated with pulmonary valve stenosis (OR: 2.4; 95% CI: 1.1 to 5.4), perimembranous ventricular septal defects (OR: 2.3; 95% CI: 1.2 to 4.6), and secundum atrial septal defects (OR: 2.4; 95% CI: 1.3 to 4.4). Untreated hypertension was associated with Ebstein malformation (OR: 2.1; 95% CI: 1.0 to 4.3) and secundum atrial septal defects (OR: 1.3; 95% CI: 1.0 to 1.6). Antihypertensive medication use and/or the underlying hypertension might increase the risk of having an infant with specific left and right obstructive and septal defects. Additional studies with adequate power will be needed to confirm these findings.

Video-assisted thoracoscopic ligation of a patent ductus arteriosus in a very low-birth-weight infant using a novel retractor

Patent ductus arteriosus (PDA) ligation is a potentially lifesaving procedure that is frequently performed in very low-birth-weight (VLBW) infants. Video-assisted thoracoscopic surgery (VATS) PDA ligation has many advantages; however, this approach has not been widely used in these extremely small patients. We present a technique using a novel retractor that allows safe VATS PDA ligation in the VLBW neonate. A 740-g male infant with necrotizing enterocolitis underwent general anesthesia. After placement in the right lateral decubitus position, he underwent a left VATS PDA ligation using a new 3-mm fan retractor for lung retraction and exposure. A thoracostomy tube was not used. He recovered uneventfully and is well at 6-month follow-up. The technique is minimally invasive and provides superior visualization of the PDA and surrounding anatomical landmarks. Using this novel retractor, VATS PDA ligation is practical in even the smallest infants. This retractor may facilitate the performance of more advanced thoracoscopic procedures in VLBW infants.

In vitro hemodynamic investigation of the embryonic aortic arch at late gestation

This study focuses on the dynamic flow through the fetal aortic arch driven by the concurrent action of right and left ventricles. We created a parametric pulsatile computational fluid dynamics (CFD) model of the fetal aortic junction with physiologic vessel geometries. To gain a better biophysical understanding, an in vitro experimental fetal flow loop for flow visualization was constructed for identical CFD conditions. CFD and in vitro experimental results were comparable. Swirling flow during the acceleration phase of the cardiac cycle and unidirectional flow following mid-deceleration phase were observed in pulmonary arteries (PA), head-neck vessels, and descending aorta. Right-to-left (oxygenated) blood flowed through the ductus arteriosus (DA) posterior relative to the antegrade left ventricular outflow tract (LVOT) stream and resembled jet flow. LVOT and right ventricular outflow tract flow mixing had not completed until approximately 3.5 descending aorta diameters downstream of the DA insertion into the aortic arch. Normal arch model flow patterns were then compared to flow patterns of four common congenital heart malformations that include aortic arch anomalies. Weak oscillatory reversing flow through the DA junction was observed only for the Tetralogy of Fallot configuration. PA and hypoplastic left heart syndrome configurations demonstrated complex, abnormal flow patterns in the PAs and head-neck vessels. Aortic coarctation resulted in large-scale recirculating flow in the aortic arch proximal to the DA. Intravascular flow patterns spatially correlated with abnormal vascular structures consistent with the paradigm that abnormal intravascular flow patterns associated with congenital heart disease influence vascular growth and function.

Cerebral palsy and congenital malformations

AIM

To determine the proportion of children with cerebral palsy (CP) who have cerebral and non-cerebral congenital malformations.

METHODS

Data from 11 CP registries contributing to the European Cerebral Palsy Database (SCPE), for children born in the period 1976-1996. The malformations were classified as recognized syndromes, chromosomal anomalies, cerebral malformations or non-cerebral malformations. Prevalence of malformations was compared to published data on livebirths from a European database of congenital malformations (EUROCAT).

RESULTS

Overall 547 out of 4584 children (11.9%) with CP were reported to have a congenital malformation. The majority (8.6% of all children) were diagnosed with a cerebral malformation. The most frequent types of cerebral malformations were microcephaly and hydrocephaly. Non-cerebral malformations were present in 97 CP children and in further 14 CP children with cerebral malformations. The most frequent groups of non-cerebral malformations were cardiac, facial clefts and limb and skeleton malformations. Children born at term had a significantly higher prevalence of cerebral malformations compared to children born before 32 weeks (12.1% versus 2.1%, p<0.001).

CONCLUSION

Cerebral malformations were much more frequent among children with CP than among all livebirths in the population. Malformations in organ systems close to the brain (eye, facial clefts) were more frequent in the CP population while malformations in organ systems further from the brain (renal, genital) were more frequent in the general population.