Unexpected Internal Mammary Vein Cannulation by an Implantable Central Venous Catheter: A Rare Complication

Central venous catheters (CVCs) play an integral role in the management of complex patients. Approximately 2% of CVC placements are improperly placed. One exceedingly rare form of malposition is placement within the internal mammary vein. Misplacement within this vein is difficult to diagnose due to its course overlying the right cardiac border on routine chest imaging, as well as being typically subclinical in presentation. We present a case of a 77-year-old female, recently diagnosed with ovarian cancer, who was referred to the surgical oncology service for placement of an implantable CVC for neoadjuvant chemotherapy. Initial implantable CVC placement was conducted via left subclavian approach, which was confirmed by routine intra-operative fluoroscopy to be overlying the right cardiac border, and presumably within the superior vena cava. Intra-operatively, the catheter was withdrawn with dark venous blood, flushed without difficulty, and the patient experienced no hemodynamic instability. The patient tolerated chemotherapy well with no complications immediately following implantable CVC placement, but there was difficulty in withdrawing blood from the port site by floor nursing on post-operative day one. Follow-up lateral view fluoroscopy discovered the catheter to be misplaced within the right internal mammary vein. This was an initial misplacement that was missed due to the anatomic course of the internal mammary vein and how it can mimic correct placement on routine intra-operative and post-operative imaging. Three weeks later, the patient underwent elective repositioning of the catheter into the superior vena cava (SVC) at the right atrial junction under fluoroscopy with additional use of Omnipaque contrast solution to ensure accurate placement. She was discharged home the same day in stable condition. This case demonstrates the importance of multiview imaging to confirm proper CVC placement. Because the right internal mammary vein overlies the right cardiac silhouette on an anteroposterior chest X-ray, the patient's implantable port appeared to be correctly placed in the SVC. Imaging modalities involving fluoroscopy or chest CT can be alternatives to confirming successful access to the SVC.