Central Venous Catheter Tracking Into a Persistent Left Superior Vena Cava in a Patient With Complete Heart Block.

Persistent left superior vena cava (PLSVC) is the most common thoracic venous anomaly, present in approximately 0.3-0.5% of the general population. Although typically asymptomatic, PLSVC carries significant procedural implications during central venous catheter (CVC) placement, pacemaker implantation, and hemodynamic monitoring. A 75-year-old man presented with symptomatic complete heart block and was transferred for pacemaker evaluation. A right internal jugular (IJ) central venous catheter was inserted for vasopressor administration. Post-procedure chest X-ray revealed the catheter coursing along the left mediastinum instead of crossing the midline. Bedside ultrasound confirmed venous placement, and arterial versus venous blood gas comparison supported correct venous cannulation. Further cardiology evaluation, echocardiography, and cardiac catheterization identified a PLSVC, explaining the aberrant catheter trajectory. Awareness of PLSVC is essential to avoid misinterpreting catheter malposition as arterial puncture or mediastinal injury. Recognizing characteristic radiographic findings can prevent unnecessary line removal and support safe procedural decision-making.