Abstract 4370663: The Curious Case of the Reverse Positive Bubble Study: A Mimicker of Persistent Left Superior Vena Cava

Persistent left superior vena cava (PLSVC) is a rare congenital anomaly, present in <1% of the population, typically draining into the coronary sinus and right atrium. When an anomalous drainage occurs into the left atrium—directly or via an unroofed coronary sinus—a right-to-left shunt may result, detected by an agitated saline (“bubble”) study from a left-sided vein. We present a rare case mimicking such a shunt. A 33-year-old man with ESRD on hemodialysis was admitted with subacute cough and weight loss, diagnosed with necrotizing MSSA pneumonia. His hospitalization was complicated by respiratory failure, septic shock, and transient effusive-constrictive pericarditis. TTE revealed an EF of 50–55%, normal RV function, small pericardial effusion, mild aneurysmal interatrial septum, and an unexpected bubble study finding: agitated saline injected via a left-arm IV resulted in bubbles first appearing in the left atrium via pulmonary veins (Figure 1), with robust left-sided opacification and delayed right-sided filling. No interatrial transit of bubbles was observed. CT angiography revealed chronic right SVC occlusion with extensive venous collaterals draining into the pulmonary veins (Figure 2), mimicking a PLSVC with unroofed coronary sinus. The SVC occlusion likely resulted from years of central venous catheterizations for dialysis. Thus, common sequelae of chronic illness produced a pattern resembling rare congenital anomalies. This case highlights the importance of careful interpretation of bubble studies, awareness of PLSVC mimickers, and the diagnostic value of multimodality imaging to avoid misdiagnosis, unnecessary testing, and patient burden. A high index of suspicion, combined with correlation across imaging modalities, is critical for accurate diagnosis and optimal patient care.