Abstract
An 88-year-old man with severe aortic stenosis and paroxysmal atrial fibrillation presented for elective dual chamber pacemaker implantation. During the procedure, an aberrant venous system was discovered. The left brachiocephalic vein was cannulated, but attempts to advance the guidewire failed due with an accessory hemiazygos vein draining into the azygous vein. Described anomalies in upper body venous return include persistent left superior vena cava (SVC), interruption of the SVC, and anomalous course of the brachiocephalic veins. This anomaly has been described twice in the literature. Congenital anomalies of thoracic veins, although usually clinically silent, can pose challenges during vascular interventions. This case highlights the importance of recognizing these anatomic variants and the impact they can have on minimally invasive thoracic surgery such as pacemaker and central line insertion.
Key Words: cardiac pacemaker, congenital heart defect, left-side catheterization
Graphical Abstract
Anatomy
Typically, venous blood from the upper body flows through the right-side superior vena cava (SVC), while blood from the lower body drains via the right-side inferior vena cava.1,2 The right and left brachiocephalic veins drain the upper limbs and head which eventually empty into the superior vena cava (Figure 1). Alongside this system exists the azygous system, which usually acts as an alternative venous drainage pathway between the upper and lower vena cavae.3,4
Take-Home Messages
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Understanding the normal anatomy and congenital abnormalities of systemic venous return is crucial for interventionalists.
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Peripheral venography is crucial for identifying such anomalies and minimizing complications during cardiac device insertion.
Figure 1.
Central Venous System
The image highlights the normal central venous drainage, showing how the left and right brachiocephalic vein connect to the superior vena cava and eventually empty into the right atrium. Public domain artwork by Mariana Ruiz Villarreal.
Pathology
The present case highlights a rare anomaly of central venous drainage. Notably there was no connection between the right and the left brachiocephalic veins (Figure 2). There was a persistent connection between the left brachiocephalic vein and the hemiazygos vein (Figure 3, Video 1). This was engorged to allow drainage of the left venous side which then emptied into the azygous vein by passing from behind the esophagus.
Figure 2.
Anatomic Variant 1
Labeled image showing the lack of connection between the left and right brachiocephalic veins, with blood draining into the hemiazygous vein.
Figure 3.
Anatomic Variant 2
Labeled photo of aberrant venous system, showing an enlarged hemiazygous vein draining the left brachiocephalic vein.
Venous anomalies are usually the cause of complex deviations in the embryologic development of the primitive venous network. The SVC develops later than other constituents of the venous system. Fusion of the venous plexus of the upper limb form the left and right anterior cardinal veins, which are connected via the inter–anterior cardinal anastomosis. Eventually there is regression of the left anterior and left common cardinal vein, leaving a persistent inter–anterior cardinal anastomosis forming the eventual connection between the left and right brachiocephalic veins and a persistent right anterior cardinal vein which forms the SVC.5
In the present case, an earlier regression on the inter–anterior cardinal anastomosis was postulated. Consequentially, the 2 brachiocephalic veins were dissociated, with an increased dependence on the hemiazygos vein to deliver right-side blood to the azygous vein and eventually the SVC or directly to the right atrium. Similar anomalies have only been described twice in the literature.5,6
Imaging Correlations and Treatment
This anomaly was noted during cine venography. During the procedure, the left pectoral site was prepared for implantation according to routine practice. Venous access was obtained by uneventful left subclavian puncture, and the pacemaker pocket was prepared. The left subclavian vein was cannulated and contrast introduced, and an aberrant venous system was noted. After this discovery, the left-side approach was abandoned, and the patient was accessed from the right. The procedure was completed without any further complications. Though uncommon, anomalous venous drainage can occasionally be observed in clinical practice. These variations may have implications for minimally invasive procedures, underscoring the significance of using cine venography.
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
Appendix
For a supplemental video, please see the online version of this paper.
Appendix
Labeled video showing the anomalous left-side venous drainage.
References
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Associated Data
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Supplementary Materials
Labeled video showing the anomalous left-side venous drainage.