Incidental Finding of a Persistent Left Superior Vena Cava During Permanent Dual-Chamber Pacemaker Implantation: A Case Report

Persistent left superior vena cava (PLSVC) is a rare congenital venous anomaly. It is often asymptomatic and has atypical venous drainage that can complicate central venous catheterisation, pacemaker implantation, and cardiac surgeries. In most cases, the PLSVC drains into the right atrium via the coronary sinus, but in a minority of cases, it drains into the left atrium, leading to a right-to-left shunt, which can cause mild hypoxia or paradoxical embolism. Due to its abnormal anatomy, PLSVC can complicate lead placement during permanent pacemaker (PPM) insertion. Lead navigation becomes more complex, sometimes necessitating alternative lead placement techniques or imaging guidance to ensure proper functionality. In most cases, the PLSVC is identified incidentally during the initial venogram. We present the case of a 64-year-old male with sarcoidosis, hypercholesterolemia, hypertension, hepatitis, and recent atrial fibrillation (AF) who presented for elective direct current cardioversion (DCCV). Pre-DCCV, the ECG showed AF with a slow ventricular response, and following a 200-joule synchronised shock as per local protocol, sinus rhythm was restored. Post-DCCV ECG showed a first-degree AV block, which progressed to an intermittent 2:1 block, leading to a decision to implant a dual-chamber PPM. An echocardiogram revealed normal left ventricular function, a dilated left atrium and normal right ventricle, mild tricuspid regurgitation, and a possible patent foramen ovale (PFO). A venogram performed during PPM implantation revealed a PLSVC, which posed challenges in lead placement. Despite initial success, a post-procedure chest X-ray revealed displacement of the atrial lead, prompting a successful repositioning. The patient remained stable and asymptomatic; outpatient follow-ups showed satisfactory PPM function. PLSVC is a congenital anomaly arising from incomplete regression of the left anterior cardinal vein during embryonic development. Though it is often discovered incidentally, the anomaly becomes clinically significant during procedures such as pacemaker implantation due to its impact on venous anatomy and lead placement. This case also underscores the need for specialised techniques when managing patients with PLSVC during device implantation. Given the abnormal venous pathway, alternative strategies such as utilising the coronary sinus or imaging guidance, like fluoroscopy, may be necessary to ensure proper lead placement and avoid complications such as lead displacement or venous thrombosis. The literature supports using advanced imaging modalities and tailored surgical approaches to improve outcomes in patients with PLSVC. Ultimately, this case illustrates the complexity of cardiac device implantation in the presence of venous anomalies and highlights the importance of individualised procedural planning to optimise patient care and reduce the risk of complications.