The persistent left superior vena cava is the most common venous anomaly in the systemic drainage in adults and tends to be asymptomatic. The persistent left superior vena cava causes rhythm disorders such as tachyarrhythmias or bradyarrhythmias.We report a case of persistent left superior vena cava diagnosed in a 53-year-old female patient admitted due to an acute coronary syndrome associated with unstable bradycardia. A transvenous peacemaker impressed the left atrium; therefore, a transthoracic echocardiogram was required to diagnose persistent left superior vena cava. The patient needed management with percutaneous intervention; she had an adequate evolution and subsequent discharge from the intensive care unit.