Hypoplastic left heart syndrome with atrial septal defect

Clinical History

A 23-year-old second gravida came for a routine prenatal ultrasound scan for first time. She did not have any complaints. No significant past medical history was present.

Imaging Findings

Left side of the foetal heart appeared hypoplastic which manifested in the following manner:

Small and hypoplastic left ventricle [Fig 1a, 1b].
Relatively large right ventricle, with small ventricular septal defect [Fig 1a, 1b].
Relatively large right atrium with atrial septal defect [Fig 1a, 1b].
Hypoplastic ascending aorta with aortic root stenosis [Fig 1c].

Patient also had mild subcutaneous tissue oedema in nape of neck which manifested as increased nuchal fold thickness, [Fig 2].

Patient also had horse shoe kidneys which were fused at their inferior poles. The kidneys demonstrated mild to moderate hydronephrosis [Fig 3].

Discussion

Hypo-plastic left heart syndrome is the most common congenital cardiac malformation detected in foetal life [1]. The incidence is between 1.7-6.7: 10, 000 live births [3]. It includes wide spectrum of cardiac malformations that range from hypoplasia to complete atresia of anatomy of left side of heart in a patient with normally related great vessels [2]. It is characterised by underdeveloped left atrium, left ventricle, mitral valve, aortic valve and aorta [3]. Oxygenated blood from lungs enters hypo-plastic left atrium via pulmonary veins. However, due to mitral valve hypoplasia, majority of the blood is shunted to right atrium via wide open foramen ovale or an atrial septal defect. So right atrium receives extra blood which is then pushed into right ventricle resulting into dilated right atrium and right ventricle. Descending thoracic aorta receives majority of the blood from main pulmonary artery via ductus arteriosus [2]. Apart from atrial septal defect, there might be concomitant patent ductus arteriosus (PDA) [5]. After the birth, ductus arteriosus undergoes constriction due to reduction in pulmonary vascular resistance. This reduces the systemic perfusion resulting into severe metabolic acidosis and cyanosis. If not treated, the affected neonate will die within 6 weeks of life [6]. Diagnosis can be made reliably by prenatal ultrasonography between 18 – 22 weeks of gestation [2]. Post natal echocardiography also plays an important role in its diagnosis [1]. The diagnostic prenatal findings include a small, thick-walled, hyper-echoic left ventricle, with weak contractility. An absent or minute left ventricle with anterior mitral leaflet, of 5 mm or less, enlarged right ventricle, absence of ante-grade flow through the aortic valve, poor motion of aortic valve; ascending aorta hypoplasia, aortic root atresia, mitral valve hypoplasia with poor valve motion [6]. Prognosis can be improved by surgical procedures like Norwood procedure, Hemi-Fontan procedure and cardiac transplantation [4]. There may be associated genitourinary, craniofacial, gastrointestinal or central nervous system anomalies [6]. Here, we present a case of second gravida who came for routine prenatal ultrasound check up at 21 weeks of gestation having hypo-plastic left heart syndrome associated with atrial septal defect, hypo-plastic mitral and aortic valves with mildly hydronephrotic horse shoe kidneys.
Take home message: Accurate diagnosis of this entity can be done by meticulous prenatal ultrasonography, which allows the obstetrician to counsel the patient for its termination, and to decide regarding post natal intervention, if the parents wish to continue with the pregnancy.

Differential Diagnosis List

Final Diagnosis

Hypoplastic left heart syndrome

URL:	https://eurorad.org/case/15391
DOI:	10.1594/EURORAD/CASE.15391
ISSN:	1563-4086