A double left BCV was first described by Subirana in 1986 . Since then, there have been few additional reports of this venous anomaly. Due to its rarity, the incidence and developmental mechanisms are not well understood . The normal left BCV originates in the transverse channel formed between the precardinal veins during the 4th to 8th week of fetal development [1, 2, 4]. Some authors have speculated that double transverse channels and their remnants might lead to the formation of a double left BCV [1, 2].
Clinically, most double left BCVs, by themselves, do not affect the patient’s condition. However, when performing the insertion of central venous catheters and electrical leads through the left subclavian vein, there may be some technical difficulties and a potential risk of venous injury due to an undiagnosed accessory left BCV [1, 2, 5].
In our present case, the accessory left BCV was diagnosed preoperatively. Therefore, we recognized the abnormal preaortic pathway of this accessory left BCV and patency of the normal left BCV. This enabled us to safely ligate the accessory left BCV prior to the intended cardiac surgical procedures. However, if the normal left BCV is hypoplastic, severely stenotic , or occluded , preservation of the accessory left BCV throughout the procedure, or transection followed by reconstruction, should be mandatory to avoid upper body congestion. In patients with an undiagnosed double left BCV, there is the risk of unexpected intraoperative bleeding due to injury of the accessory left BCV, particularly if it has a preaortic course.
For the establishment of cardiopulmonary bypass, there are some technical issues in patients with double left BCVs. There is a potential risk of inadequate venous drainage due to the obstruction of the aberrant BCV opening at the superior vena cava by the venous cannula itself . Differentiating between the accessory left BCV and persistent left superior vena cava is also important to determine the necessity of additional venous cannulas for use in a cardiopulmonary bypass.
Preoperative venous evaluation is important in patients undergoing cardiac surgical procedures [1, 4]. Contrast-enhanced multidetector CT images are useful for the precise, preoperative diagnosis of left BCV anomalies . The possibility of misidentifying an accessory left BCV as a mediastinal lymph node on unenhanced CT has been suggested as a potential risk [4, 7].
Although the double left BCV is rare, cardiovascular surgeons should be aware of this venous anomaly to avoid several intraoperative complications.