INTRODUCTION: Isolated drainage of the superior vena cava (SVC) into the left atrium is an extremely rare finding, with only 15 cases reported in the literature. The majority of reports describe this anomaly in adolescents; the number of adults diagnosed with this congenital abnormality is very few. We report a 66-year-old female referred for obstructive sleep apnea who was found to have such an anomaly.
CASE PRESENTATION: The patient is an obese 66-year-old female with a past history of breast cancer, treated with left mastectomy, who was seen for evaluation of obstructive sleep apnea syndrome (OSAS). A polysomnogram showed sleep apnea with desaturation well out of proportion to the degree of apnea. Complaints included restless sleep with frequent awakenings, bifrontal headaches, and dyspnea with exertion. Pulmonary function tests demonstrated normal spirometry, normal diffusing capacity, and lung volumes significant for a reduced expiratory reserve volume. Physical examination was remarkable for weight of 281 pounds, and room air oxygen saturation of 91%. There was no jugular venous distension, heart sounds were regular, no murmurs were auscultated, and the chest was clear. There was no cyanosis. A chest x-ray was unremarkable. An arterial blood gas showed a pH of 7.40, pCO2 of 42, and a pO2 of 62 on room air. Given the degree of hypoxia, the patient underwent further testing. A chest CT scan, did not show any parenchymal disease, but did show a persistent left sided SVC. A 100% oxygen shunt study found a shunt of 26%. A nuclear perfusion shunt scan with macroaggregated albumin revealed marked tracer uptake in extra pulmonary tissue when injected into the right arm - 92% of the tracer was present outside of the lungs. A transthoracic bubble echocardiogram demonstrated contrast entering the left atrium directly after injection in the right antecubital vein. A transesophageal echocardiogram confirmed a left sided SVC entering an enlarged coronary sinus, and a right-sided SVC entering the left atrium. Injection of contrast in the right arm confirmed communication of the right SVC with the left atrium. Contrast injection in the left arm showed communication of the left SVC with the coronary sinus.
DISCUSSIONS: This report details a 66-year-old female who was found to have a congenital large vessel right to left shunt with drainage of the right SVC into her left atrium. Only 15 similar cases have been reported. This patient appears to be the oldest reported patient with this rare abnormality. Embryologists theorize that malposition of the right horn of the sinus venosus in a leftward and cephalic direction, with subsequent connection of the dominant SVC to the left atrium, rather than the right atrium, underlies this anomaly. Of clinical importance, the patient had been advised to avoid all intravenous infusions and utilization of the veins of her left arm given her mastectomy on that side. Given the above findings, the patient was advised to avoid infusion into her right arm to decrease the risk of systemic embolization in the presence of the right to left shunt.
CONCLUSION: This case highlights the fact that wakeful hypoxemia is not consistent with pure OSAS and should prompt the clinician to explore this further. Evaluation in this case pointed to a right to left shunt and the diagnosis of an extremely rare congenital malformation, undetected well into adulthood.
DISCLOSURE: Nehal Thakkar, None.