Case report

A 65-day-old girl visited the emergency room due to poor oral intake and lethargy. Chest radiography revealed cardiomegaly (Fig 1a). Echocardiography revealed a hypoplastic left atrium, left ventricle, aortic valve (6 mm; Z-score, −1.88), and mitral valve (8.6 mm; Z-score, −2.53) (Fig 2a). Suspecting hypoplastic left heart syndrome, the patient was admitted to the paediatric ICU. On admission, the patient’s body weight was 4.5 kg. Initial blood pressure was 65/29 mmHg; heart rate, 162/min; respiratory rate, 62/min; and oxygen saturation, 86%. After intubation, blood pressure decreased to 40/26 mmHg and lactate levels increased from 1.5 to 4.3 mmol/L. Central venoarterial extracorporeal membrane oxygenation support was required because hypotension persisted despite using high doses of inotropes (dopamine, 15 µg/kg/min; dobutamine, 15 µg/kg/min; epinephrine, 0.4 µg/kg/min). After stabilising vital signs using extracorporeal membrane oxygenation, a detailed echocardiography detected a membrane dividing the left atrium into two chambers, indicating cor triatriatum sinister (Fig 2a). Scanty mitral inflow through a 2 mm hole in the membrane resulted in a hypoplastic left ventricle and low cardiac output. Cardiac CT confirmed a dilated proximal chamber and small distal chamber, which was also compressed by an enlarged coronary sinus (Fig 2c and d). After extracorporeal membrane oxygenation support for four days, end-organ functions recovered, and a corrective surgery was performed (Supplementary Fig 1). After complete resection of the membrane in the left atrium cavity, we left a 4–5 mm of fenestration on the atrial septum to prevent pulmonary oedema due to acute volume overload on the small left atrium. The mitral valve was small but showed acceptable leaflet motion and the size of the left heart increased enough to support systemic circulation (Fig 2b). Weaning from cardiopulmonary bypass was uneventful and the patient was transferred to the paediatric ICU without extracorporeal membrane oxygenation support. The patient was extubated on postoperative day 4 and discharged on postoperative day 10. Cardiomegaly improved on pre-discharge chest radiography (Fig 1b), and left ventricle end-diastolic diameter increased from 8.2 mm (Z-score, −8) to 19.2 mm (Z-score, −0.39) on pre-discharge echocardiography. The brain natriuretic peptide levels decreased from 12,582 pg/mL to 844 pg/mL at discharge. However, the patient visited the outpatient clinic 4 months after discharge, wherein respiratory difficulty was observed. Although chest radiography showed mild pulmonary congestion (Fig 1c), echocardiography revealed severe pulmonary hypertension with multiple pulmonary vein stenosis; both upper pulmonary vein flows were not visible, and the pressure gradient on the right and left lower pulmonary veins was 9.5 mmHg and 3.5 mmHg, respectively. Cardiac CT confirmed total occlusion of both upper pulmonary veins and stenosis in both lower pulmonary veins (Fig 2e and f). Percutaneous balloon angioplasty was impossible because a previously left atrial septal defect was spontaneously closed. We decided to perform a hybrid pulmonary vein angioplasty, comprising a surgical approach to the left atrium and subsequent ballooning or stenting in the stenotic pulmonary veins under direct vision through the open left atrium. In the operative field, most of the left atrial endocardium showed fibrotic changes. Additionally, the openings of both upper pulmonary veins appeared almost closed (Supplementary Fig 2). The smallest Bowman probe (1 mm) could barely enter the upper pulmonary vein openings. Once the probe penetrated, we could make the opening larger step-by-step with one size larger probe. Then, we surgically managed the opening and extended the incision until we reached the relatively larger lumen. However, the stenotic portion of pulmonary vein was significantly longer than anticipated and it seemed almost reached the lung parenchyma. The vessel wall of pulmonary vein was also severely thickened. Following the surgical venous opening, we decided to add stents as a primary treatment option because we thought surgical widening alone would not be effective. After balloon angioplasty using a 4 mm-sized Sterling™ Balloon Dilatation Catheter (Boston Scientific Corporation, MA, USA) in the right upper pulmonary vein, we placed a 4.5 mm diameter and 12 mm length Resolute Onyx Zotarolimus-Eluting Coronary Stent (Medtronic Cardiovascular Ltd., CA, USA). Ballooning and stenting in the left upper pulmonary vein were performed in the same manner. However, ballooning in the left lower pulmonary vein with a 7 mm-sized Sterling™ Balloon Catheter crushed the stent in the left upper pulmonary vein, for which we had to remove that crushed stent. Finally, we performed ballooning in the right lower pulmonary vein and made a fenestration in the atrial septum. Postoperative chest radiography showed that the distal portion of the stent in the right upper pulmonary vein was not fully dilated. Therefore, we attempted transcatheter balloon angioplasty for further dilatation of the stent. We administered sirolimus (0.8 mg/m²) to prevent proliferation of fibroblasts. ^{Reference Patel, Briones and Mandhani1} However, the pulmonary vein stenosis progressed despite repeated balloon angioplasty every month. Three months after the first hybrid procedure, we performed a second hybrid procedure for stenting in the right lower pulmonary vein with a 7 mm diameter and 15 mm length stent (PALMAZ BLUE, Cordis, Bridgewater, NJ, USA) and ballooning in the left pulmonary veins. Even with this procedure, extracorporeal membrane oxygenation support was required due to severe hypoxaemia and right ventricular failure (Fig 1d). We registered the patient for heart-lung transplantation due to the intractable pulmonary vein stenosis and severe fibrotic endocardial change in the left atrium. She had experienced many complications associated with extracorporeal membrane oxygenation for 3 months and eventually expired of uncontrolled gastrointestinal haemorrhage.

Figure 1. Chest radiography. ( a ) Initial chest radiography showing severe cardiomegaly, with a cardiothoracic ratio of 74.2%. ( b ) At discharge, the cardiothoracic ratio decreased to 63.3%. ( c ) At the 4-month follow-up, pulmonary congestion develops. ( d ) The last chest radiography showing aggravated pulmonary congestion on central venoarterial extracorporeal membrane oxygenation. The distal part of stent on the right upper pulmonary vein is not fully dilated, and the vein is finally occluded. The right lower pulmonary vein stent is patent. However, there is severe in-stent stenosis on the last echocardiography due to intimal proliferation.

Figure 2. Echocardiography and cardiac CT angiography. ( a ) Apical four-chamber view of echocardiography showing hypoplastic left atrium and ventricle with severe right atrial and ventricular enlargement. The cor triatriatum membrane is visible in the left atrium (red arrow). ( b ) After resecting the cor triatriatum membrane, the size of the left atrium and ventricle increased significantly. ( c ) Preoperative CT angiography showing a membrane in the small left atrium (red arrow). ( d ) The membrane is located distal to the left atrial appendage. ( e ) and ( f ) Postoperative CT shows occlusion of both upper pulmonary veins (red arrowheads). CS, coronary sinus; ECMO, extracorporeal membrane oxygenation; LA, left atrium; LV, left ventricle; RA, right atrium; RUPV, right upper pulmonary vein; RV, right ventricle.