Late-Detected Sinus Venosus Atrial Septal Defect and Subsequent Enteroviral Central Nervous System Infection: A Case Report.

Sinus venosus atrial septal defect (SVASD) is frequently associated with partial anomalous pulmonary venous return and may be missed on routine transthoracic echocardiography because of its superior and posterior location. We report a 68-year-old woman with atrial fibrillation who presented with dyspnea and marked right-sided chamber enlargement. Cardiac magnetic resonance imaging identified a 33 × 21-mm superior SVASD, anomalous drainage of the right upper and middle pulmonary veins, and a persistent left superior vena cava. The Qp/Qs was 3.7 by cardiac magnetic resonance and 3.2 by right heart catheterization, with a low indexed pulmonary vascular resistance of 1.7 Wood units·m², supporting surgical repair. Three and a half months after successful repair, the patient presented with transient loss of consciousness. Cardiac evaluation showed no residual interatrial shunt, no intracardiac thrombus, and no significant arrhythmia, although right ventricular dysfunction persisted. Brain magnetic resonance imaging demonstrated asymmetric cortical and deep gray matter abnormalities. Cerebrospinal fluid showed lymphocytic pleocytosis, mildly elevated protein, preserved glucose, and positive enterovirus polymerase chain reaction. These findings supported enteroviral central nervous system infection. Because atrial fibrillation and postoperative cardiac abnormalities provided competing explanations for the neurologic presentation, the exact mechanism of the transient loss of consciousness remained uncertain. This case illustrates the importance of avoiding diagnostic anchoring when new neurologic symptoms develop after congenital cardiac surgery.