CC is a 31 year old primigravida who was referred for ultrasound at a community hospital due to suspected cardiac anomalies noted on a screening sonogram at her doctor's office. Due to concern about a probable cardiac abnormality an amniocentesis was performed at the local hospital.
The amniocentesis showed trisomy 21, and the patient was referred to the Yale Fetal Cardiovascular Center due to the suspected cardiac anomalies.
When first seen at Yale, the patient was 21 weeks gestation. The nuchal skin fold measured 7.7 mm, and the humerus lagged gestational age slightly. The remainder of the extracardiac anatomy was unremarkable.
The four chamber view of the heart was remarkable for an absence of the lower atrial septum, a common atrioventricular valve, and a ventricular septal defect. Venous return to the heart was normal, as were the great arterial connections. Color Doppler flow study showed good flow into both ventricles, and there was only a moderate ventricular septal defect. Neither ventricle dominated at the apex of the heart.
The fetus was diagnosed to have a complete atrioventricular (AV) septal defect (also known as an AV canal defect, or an endocardial cushion defect). The absence of disproportion in sizes of the ventricles, with neither dominating at the apex of the heart and a good residual portion of the ventricular septum indicated that this was a balanced defect, as distinguished from an unbalanced defect. This latter variation has a much worse prognosis, while trisomy 21 is more common with the better prognosis balanced defects.
Follow-up ultrasounds showed no change in appearance, with no evidence of valve regurgitation, which is important to evaluate as it may lead to fetal hydrops (Gembruch, 1991). The patient went into spontaneous labor at 37 weeks gestation, and had an uneventful normal spontaneous vaginal delivery. The baby remained in hospital for 4 days due to slow feeding, but was discharged home on no medications.
The association between Down syndrome and cardiac anomalies has been known for many years (Rowe, 1961). That there is a disproportionate risk of fetal aneuploidy when fetal heart disease is present was first recognized by Wladimiroff (1985), and corroborated by our group at Yale in a larger series (Copel, 1988). We counsel patients that overall about 25 30% of fetuses with heart disease have abnormal karyotypes, and with certain combinations, such as in this fetus with an AV septal defect and slight lag in growth of the long bones the risk may be over 50%. Recent descriptions of small deletions detectable only by flourescent in situ hybridization (FISH) among fetuses and children with DiGeorge syndrome Wilson, 1992; Driscoll, 1993) has raised the idea that many cardiac anomalies may be due to single gene defects that are not present or not expressed in the parents.
The prognosis for children with balanced AV septal defects is quite good. At birth there may be some degree of cyanosis, varying with the amount of mixing of arterial and venous blood that may be present. Surgical intervention can be deferred to allow growth of the child, although as pulmonary vascular resistance drops postnatally there will be gradual onset of pulmonary congestion which can be managed initially with digitalis and diuretics. Pulmonary artery banding can also help buy time until later in the first year after birth by reducing the pressure of blood reaching the lungs and preventing the development of pulmonary hypertension. Open heart surgery to repair the defect is done later.
Four chamber view obtained at 26 weeks gestation. IVS - interventricular septum, LV - left ventricle, RV - right ventricle. Note absence of lower atrial septum and straight line appearance of common AV valve. Normally the tricuspid valve insert onto the ventricular septum closer to the apex of the heart than does the mitral valve.
Four chamber view obtained at 32 weeks gestation. The extent of the ventricular septal defect can be seen as indicated by the two arrows. Other details of image are similar to other figure. (Click on each image to view larger version)