BACKGROUND The persistence of a vein of Marshall (VoM) from the left subclavian vein to the coronary sinus is a rare cardiac anomaly known as a persistent left superior vena cava (PLVC). This anatomical variant is usually asymptomatic but can lead to serious complications during catheterization via the left subclavian or internal jugular vein, as described here. In our case, the patent vein of Marshall directly connected the coronary sinus with the left subclavian vein discovered in a cardiac arrest patient because of pericardial effusion during the insertion of a central venous catheter (CVC). CASE REPORT A 62-year-old patient required a central line insertion through a left internal jugular vein. The patient immediately went into cardiac arrest after CVC insertion with a pericardial effusion. The patient was successfully resuscitated with the drainage of a pericardial effusion. A chest X-ray revealed that the central venous catheter (CVC) was located along the left border of the mediastinum rather than the right border. It was evident that the central venous catheter was inadvertently placed into the pericardial space, resulting in tamponade. This complication occurred through inadvertent access of a small persistent vein of Marshall. CONCLUSIONS This case illustrates the importance of knowledge of anatomical variants of the persistent vein of Marshall to prevent or correctly interpret and manage procedural complications.