Teaching Case

Routine 19 week antenatal scan, postnatal dyspnoea.

The patient presented with her 4th uneventful pregnancy for a routine 19 week antenatal anomaly scan. The following abnormalities were seen: enlargement of the cerebral ventricles and increased nuchal soft tissues (Fig. 1), cardiac atrioventricular septal defect (AVSD) (Fig. 2), echogenic kidneys (Fig. 3), polydactyly and broad first toes (Fig. 4). Trisomy 21 was confirmed by amniocentesis. At birth the baby girl had dysmorphic features typical of Down's syndrome but no evidence of heart failure. At 6 days of age a grade 2/6 systolic murmur was evident. Chest x-rays showed increasing pulmonary plethora in keeping with a left-to-right shunt, as well as only 11 pairs of ribs (Fig. 5). The patient had a low birth weight and subsequently poor weight gain and gradually developed clinical signs of heart failure with an increasingly loud murmur, tachycardia, chest recession and tracheal tug. Echocardiography confirmed the presence of a ventricular septal defect (VSD). She was readmitted at 7 weeks and was started on furosemide and captopril and subsequently underwent surgery to repair the heart defect at 5 months of age.

Cardiac anomalies are the most common group of congenital structural malformations, occurring in 8/1000 live births. Of these VSD is the most common (32%), followed by a patent ductus arteriosus (PDA).
8% of cases are associated with a chromosomal abnormality and therefore if a defect is observed antenatally, other anomalies need to carefully excluded and chromosomal analysis considered.
Trisomy 21 (Down's syndrome) occurs in 1/700 births and is commonly diagnosed antenatally. 40% of Down’s babies have congenital heart defects of which defects of the endocardial cushion are the most common. Clinical features include characteristic flat facial appearance, broad hands with a single palmar crease, malformed ears, a speckled iris (Brushfields spots) and hypotonia in infancy. Mental retardation is common but not universal.
The 3 principle findings on chest radiography of a patient with Down's syndrome are evidence of congenital heart disease, hypersegmentation of the sternum, with two ossification centres (90%), and 11 pairs of ribs (25%). Other common skeletal anomalies include: an abnormal iliac index; atlanto-axial subluxation (25%); and short tubular bones in the hands with clinodactyly (50%) and hypoplasia of middle phalanx of the little finger (60%). Gastrointestinal findings include umbilical hernia, duodenal atresia or stenosis (double bubble sign), annular pancreas, tracheo-oesophageal fistula, anorectal anomalies and Hirschsprung’s disease.