Commentary: Anomalies of Systemic Veins: A Topic of Interest to the Anesthesiologist

Anomalies of the systemic venous drainage constitute a wide range of heterogenous malformations. Regarding phenotypic variability, it is essential to distinguish between the lesions producing partially as opposed to totally anomalous drainage, with the sinus venosus defects being a key component of the spectrum.[1] The anomalies are particularly significant to anesthesiologists, as the resulting physiological consequences may similarly be variable. Dependent on the shunting produced, either of the ventricles may be subjected to volume overload. The magnitude of the right-to-left shunt, in turn, will determine the degree of arterial oxygen desaturation. In this commentary, we emphasize the anatomical features of the critical lesions.

Our first example illustrates the consequences of partially anomalous systemic venous return. A computerized tomography investigation, including angiography in a preschool child, reported the absence of the proximal part of the right superior cava vein. The venous return through the cranial part of the right superior cava vein was diverted through the brachiocephalic vein to the left superior cava vein. As is typically the case, the left superior cava vein was connected to the coronary sinus.[2,3] In this child, however, the coronary sinus was wholly unroofed. Consequently, all the venous return from the upper body was draining anomalously to the roof of the morphologically left atrium. The inferior cava vein was draining in standard fashion to the morphologically right atrium [Figure 1a], with the pulmonary veins connected to the left atrium [Figure 1b]. The bronchial anatomy was normal, confirming the presence of the usual arrangement. The transthoracic echocardiography revealed concordant atrioventricular and ventriculo-arterial connections and an unbalanced atrioventricular septal defect. The child presented with a resting arterial oxygen saturation of less than 70%; so, oxygen supplementation was needed. The child went successfully through the stages of functionally univentricular surgical palliation. The case shows that, although the venous return from the upper body was to the coronary sinus, the unroofing of its walls resulted in anomalous drainage. Had the coronary sinus retained its typical walls, discrete from the walls of the morphologically left atrium, the venous return would have been normal, with no impact on the arterial saturation. Persistence of the left superior cava vein, of course, can create problems for the surgeon even if correctly connected. Our first case, therefore, emphasizes the need to distinguish between anomalous systemic connection and anomalous systemic drainage.

Figure 1.

(a and b) Computed tomographic frontal view displaying the continuation of the right superior cava vein diverted through the brachiocephalic vein to the left superior cava vein, which was connected to the morphologically left atrium through a completely unroofed coronary sinus and the inferior cava vein draining in normally into the morphologically right atrium [a], with the pulmonary veins connected normally to the left atrium [b]

Our second case shows that the systemic veins can be connected anomalously, thus producing anomalous systemic venous drainage.[1] In the usual atrial and bronchial arrangement setting, the lesion is characterized by the connection of both cava veins, the hepatic veins, and the coronary sinus to the morphologically left atrium. When the atrial arrangement is usual, all pulmonary veins connect to the morphologically left atrium [Figure 2a and b]. When present as an isolated anomaly, the left-to-right shunting, through an atrial septal defect, a ventricular septal defect, or a persistently patent arterial duct, determines the systemic oxygen saturation levels. The magnitude of the shunt determines the sizes of the right atrium and right ventricle.[4] The electrocardiogram may show an early ’QRS complex transition in the precordial leads, suggesting an enlarged left ventricle with a small right ventricle. Transthoracic echocardiography may show a dilated left ventricle, with the right-sided chambers underfilled. These patients, admittedly rare, will frequently need an urgent atrial septostomy in the neonatal period. An essential pointer to the correct diagnosis may be that the low arterial oxygen saturation is not responsive to supplemental oxygen therapy.

Figure 2.

(a and b) Computed tomographic frontal view displaying the normal bronchial anatomy [a] and 3D reconstruction posterior view showing the right superior cava vein, hepatic veins, the inferior cava veins, and the pulmonary venous confluence draining to the morphologically left atrium with none of them entering the right atrium which lies anterior to the plane of the interatrial septum [b]

For our final example, we choose a lesion that can produce partially anomalous systemic drainage but depends on partially anomalous pulmonary venous drainage. This is the sinus venous defect, which we have already mentioned. Found almost always with the usual atrial arrangement but also as the mirror-imaged variant, the lesion can underscore a spectrum of physiological disturbance. This will depend on whether the cava vein involved in the lesion is connected predominantly to the morphologically right or the morphologically left atrium. The venous connection is often balanced, with the orifice overriding the rim of the oval fossa. We now know that the defect results from a partially anomalous connection of one or more of the right pulmonary veins, thus creating the veno-venous bridge, which allows the systemic venous tributary to drain partially or totally into the morphologically left atrium.[5,6] We show a computerized tomographic angiogram, with a three-dimensional reconstruction, as an example from a child with the usual atrial arrangement. The right superior cava vein, having received the anomalous connections of the right upper and middle lobe pulmonary veins, which retained their left atrial connections, was draining into the morphologically left atrium, thus producing a right-to-left shunt. The inferior cava vein retained its regular connection to the morphologically right atrium [Figure 3a], as did the coronary sinus. In this instance, however, the coronary sinus received venous drainage through the left superior cava vein. As its walls were not unroofed, the drainage went to the morphologically right atrium [Figure 3b]. It might be anticipated that this combination, producing a left-to-right shunt, would be associated with arterial desaturation. Surprisingly, the child was asymptomatic, and the defect was identified while investigating a heart murmur. As the pulmonary veins were mostly draining to the left atrium, there was a left-to-right shunt across the interatrial communication. The child underwent a successful Warden procedure.

Figure 3.

(a and b) Sagittal computed tomographic image showing the superior cava vein connected to the morphologically left atrium, with the inferior cava vein connected to the right atrium, with associated superior sinus venosus and the inferior cava vein retaining its normal connection to the morphologically right atrium [a] and a 3D reconstruction demonstrating the coronary sinus receiving venous drainage through the left superior cava vein, and as its walls were not unroofed, the drainage was again to the morphologically right atrium [b]

Isolated drainage of the inferior cava vein into the left atrium is a rare congenital disorder. The lesion presents as arterial desaturation with no cardiac murmurs. It is usually the consequence of the persistence of a large Eustachian valve, deflecting the inferior cava venous return through the oval fossa. Alternatively, the inferior cava vein can override the rim of the oval fossa when there is an inferior sinus venosus defect. The phenotypic variants should be distinguished echocardiographically.[7,8]

Various combinations, therefore, must be anticipated to produce anomalous systemic venous drainage. It is always important to distinguish between systemic venous connections and systemic venous drainage. The critical feature of a total anomalous systemic venous connection is that the coronary sinus also needs to be connected with the left atrium. It is also essential to recognize the isomeric arrangement of the atrial appendages, if present—the key feature of so-called heterotaxy. When the appendages are isomeric, then, of necessity, either the pulmonary or systemic veins will be anomalously connected in terms of the underlying anatomy. The patterns of return drainage can mimic the arrangements found with lateralized atrial appendages. There is critical to remember that abnormal drainage of the inferior cava vein can result from the Eustachian valve’s persistence. This can deflect the inferior cava venous return to the morphologically left atrium through a persistently patent oval fossa. Care thus needs to be taken to ensure that during surgical closure of the oval fossa, the surgeon does not close the space between the Eustachian valve and the septum.

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