A unique bizarre subtype of mixed total anomalous pulmonary venous connection

Abstract

Mixed total anomalous pulmonary venous connection is a rare CHD with a wide variation in pulmonary venous anatomy and drainage. We present a ten-day-old newborn with a rare bizarre subtype of mixed total anomalous pulmonary venous connection.

Total anomalous pulmonary venous connection is a cardiac pathology that accounts for less than 1% of all CHDs, in which the pulmonary veins drain into the systemic veins, right atrium, or coronary sinus instead of the left atrium. Four types of total anomalous pulmonary venous connection were identified: anomalous connection at the supracardiac, cardiac, infracardiac, and two or more of the above levels (mixed). ^1,2

Mixed total anomalous pulmonary venous connection is rare, accounting for only 5% of diagnosed total anomalous pulmonary venous connection. Although the morphologic heterogeneity of the venous connections, incomplete ascertainment of the anatomy, length of the confluent chamber, presence or absence of obstruction, and surgical treatment modalities have been implicated as the causative factors for continuing high mortality, there is as yet insufficient appreciation of the entire spectrum of mixed total anomalous pulmonary venous connection. ^1,2

The diagnosis and treatment of mixed total anomalous pulmonary venous connection are still challenging and can be daunting. ³ We present a ten-day-old newborn with a rare bizarre subtype of mixed total anomalous pulmonary venous connection. This unique and very rare total anomalous pulmonary venous connection’s morphological features were demonstrated by echocardiography and CT.

Case report

A ten-day-old male patient without antenatal follow-up was born at the 40th week of gestation with a weight of 3200 g by caesarean section. He was consulted by paediatric cardiology due to respiratory distress and cyanosis. On physical examination, 1/6 systolic murmur was present, and the oxygen saturation at room air was 88%. Electrocardiogram showed normal sinus rhythm with the right-axis deviation. Situs solitus levocardia, atrioventricular, and ventriculo-arterial concordance was demonstrated in transthoracic echocardiography. Transthoracic echocardiography revealed an 8 mm measured secundum-type atrial septal defect with a right to left shunt. Pulmonary veins were drained to the left (brachiocephalic vein) and right (directly to the superior vena cava) vertical veins at the supracardiac level and to the hepatic veins through a large third vertical vein without obstruction on colour and PW Doppler (Fig 1a–c). The aortic arch was left-sided, and a 3 mm measured patent ductus arteriosus was observed. Further imaging with CT confirmed echocardiographic diagnosis (Fig 2a–b). Pulmonary venous drainage was schematised in Figure 3.

Figure 1. Transthoracic echocardiogram on admission: ( a ); ( b ) ( c ) confluence connection with the vertical vein.

Figure 2. Computed tomography angiogram: ( a ) confluence of vertical vein ( b ) three-dimensional reconstruction. A = anterior; F = foot; L = Left; P = posterior; R = right *vertical vein.

Figure 3. The pulmonary vein drainages are shown in the illustration. BCV = brachiocephalic vein; HV = hepatic vein; LIPV = left inferior pulmonary vein; LSPV = left superior pulmonary vein; RA = right atrium; RIPV = right inferior pulmonary vein; RSPV = right superior pulmonary vein; SVC = superior vena cava; VV = vertical vein.

Cardiopulmonary bypass was commenced with ascending aortic perfusion and bicaval cannulations. Moderate hypothermia was induced. Measures to ensure myocardial protection included del Nido cardioplegia solution. All vertical veins were divided. The right inferior pulmonary vein and left inferior pulmonary vein were anastomosed to the left atrium with the biatrial approach. The atrial septal defect was closed using a pericardial patch. Since the right superior pulmonary vein is remote, it is passed over the right pulmonary artery and anastomosed to the right inferior pulmonary vein. The left superior pulmonary vein was anastomosed directly to the left atrium with the conventional approach. The postoperative recovery was uneventful.

Discussion

Total anomalous pulmonary venous connection is a rare congenital anomaly, corresponding to approximately 1% of all CHDs. Failure of the common pulmonary vein to connect with the pulmonary venous plexus leads to the persistence of one or more earlier venous connections to the right SVC, to the left vertical vein/innominate vein, or to the umbilicovitelline vein/portal vein. ^1,2

The surgical approach varies for different types of mixed total anomalous pulmonary venous connection. Accurate diagnosis, especially regarding all four pulmonary veins drainage, has been emphasised as a critical factor for achievement. ³ Chowdhury et al., who reported the largest mixed total anomalous pulmonary venous connection series in the literature, categorised three subtypes to facilitate classification and improve surgical outcomes. ⁴ Similarly, St Louis et al modified classification. ⁵ Type IV A (Category I): Bilateral and symmetrical connections. This group of patients had separate anomalous connection of veins from each lung: “2 + 2” pulmonary venous drainage pattern. Type IV B (Category II): Bilateral and asymmetrical connections. This group of patients had isolated drainage of a solitary pulmonary vein and drainage of the other three pulmonary veins to a common site: “3 + 1” pulmonary venous drainage pattern. Type IV C (Category III): Bizarre anatomic variants. This group of patients had bizarre anatomic variants.

Our cases' morphological features were confident with the bizarre anatomic variant, as shown in Fig 3, and can be symbolised as 2 + 1 + 1. As far as our knowledge, this is a unique and previously undefined form of total anomalous pulmonary venous connection.

Echocardiography can provide anatomical details regarding the position of anomalous pulmonary venous connections and the presence of a venous obstruction in the majority of patients. In most cases, echocardiography is sufficient and preferable, but sometimes it can only identify two or three veins, leading to misdiagnosis. Some reports ⁶ have shown that the mixed type is the most challenging type, with 44.4% of patients diagnosed only after the surgical examination. ³ In order to identify all four veins, CT angiography, which can provide not only an accurate description of the pulmonary venous drainage pattern but also delineate the pulmonary vein anatomy in patients with suspected asymmetrical pulmonary venous obstruction, should be applied despite the radiation exposure. ⁷ The merit of CT angiography is three-dimensional reconstruction, which can provide a precise non-invasive visual description of the pulmonary vein connections. ⁷

In our case, anatomy was suspected by echocardiography and detailed with CT angiography.

As a result, surgical success in mixed total anomalous pulmonary venous connection, especially in patients with more complex pulmonary venous connections, could be achieved with complementary imaging methods such as echocardiography and three-dimensional CT.