Isolated right ventricular hypoplasia associated with cyanotic atrial septal defect: a case report

Abstract

Background: Hypoxaemia in isolated right ventricular (RV) hypoplasia (IRVH) is primarily caused by a right-to-left shunt (RLS) at the atrial level, such as an atrial septal defect (ASD). When considering closure of the RLS, it should be closed only after ensuring that it will not cause right-sided heart failure (HF).

Case summary: A 21-year-old woman had been experiencing shortness of breath during exertion since childhood. Transthoracic and transoesophageal echocardiography revealed an ASD with bidirectional shunting, and microbubble test revealed a marked RLS. Cardiac magnetic resonance imaging revealed a hypoplastic RV end-diastolic volume corrected for body surface area of 47 mL/m² (70% of normal range). Right heart catheterization revealed a decreased Qp/Qs ratio of 0.89 and a pressure waveform with a clear increase in the 'A'-wave, although the mean right atrial pressure was not high (4 mmHg). Therefore, the patient was diagnosed with cyanotic ASD and IRVH. A temporary balloon occlusion test was performed to evaluate the right-sided heart response to capacitive loading prior to ASD closure. After treatment, the patient's improved markedly. The pre-operative brain natriuretic peptide (BNP) level was normal; however, 6 months after ASD closure, the BNP level was elevated, and the continuous-wave Doppler waveform of pulmonary regurgitation at the time of transthoracic echocardiography changed, suggesting an increase in diastolic RV pressure.

Discussion: When ASD is complicated by hypoxaemia, the possibility of IRVH, although rare, should be considered. Another difficult point is determining whether the ASD can be closed, considering its immature RV compliance.

Keywords: Balloon occlusion test; Case report; Cyanotic atrial septal defect; Isolated right ventricular hypoplasia.

Figure 1

(A) Chest X-ray photograph showing a slightly enlarged cardio-thoracic ratio of 56%. (B). Electrocardiogram on admission showing a normal sinus rhythm of 53 b.p.m. without any bundle branch blocks. (C) Transthoracic echocardiography at rest showing a Grade 4 right-to-left shunt at the atrial level. (D) Colour Doppler flow imaging of transoesophageal echocardiography showing a bidirectional shunt through the atrial septal defect.

Figure 2

(A) Presenting oxygen saturation (%) under 3 L/min of oxygen administered by mask. Oxygen saturation increased in the right atrium and decreased from the pulmonary vein to the left atrium. (B) Pressure (mmHg) in each lumen of the right heart catheter is shown immediately after hospitalization. Each atrium and vein presents the mean pressure, whereas the ventricles, aorta, and pulmonary artery show systolic/diastolic pressure data. PVR, pulmonary vascular resistance. (C) The pressure waveforms by right heart catheterization showed a significant increase of ‘A’-wave in the right atrial pressure wave and dip-and-plateau pattern in the right ventricle. RA. right atrium; RV, right ventricle; LV, left ventricle; EDP, end-diastolic pressure. (D) Right heart catheter at ASD closure after volume loading with 500 mL normal saline shows oxygen saturation increases without any increase in central venous pressure or right atrial or ventricular pressure. PCWP, pulmonary capillary wedge pressure; ASD, atrial septal defect.

Figure 3

The upper panel is a weakly magnified Masson stain (×40) showing mild stromal fibrosis. The lower panel is a strongly magnified (×200) haematoxylin eosin-stained section showing a marked discrepancy in cardiomyocyte diameter.

Figure 4

The change of continuous-wave Doppler waveform of the pulmonary regurgitation between before and after the atrial septal defect closure shows a steep decrease in pressure gradient suggesting an increase in diastolic right ventricular pressure.