Unmasking an Intracardiac Shunt in a Case of Persistent Unexplained Hypoxia: A Case Report

Background and Clinical Significance: Pulmonary hypertension (PH) is characterized by an increase in mean pulmonary arterial pressure and pulmonary vascular resistance. It is frequently encountered in patients with significant intracardiac shunts, often necessitating the implementation of a closure device or surgical correction. Nevertheless, the occurrence of a concomitant atrial septal defect (ASD) with a right-to-left shunt inducing left ventricular dysfunction is a rare phenomenon. Case Presentation: A 69-year-old female patient with a history of heart failure (with preserved ejection fraction) and end-stage renal disease on hemodialysis presented to an outside facility, with syncope and hypoxia. She was recently diagnosed with severe pulmonary hypertension (measuring 86 mmHg). Right heart catheterization (RHC) revealed precapillary pulmonary hypertension (88/37/54 mmHg), prompting the initiation of intravenous epoprostenol. Nevertheless, the patient was persistently hypoxic, raising the possibility of a concomitant diagnosis. Upon review of the prior echocardiogram, which included a bubble study, an intracardiac shunt was identified. It was hypothesized that a combination of right ventricular failure and the right-to-left shunt resulting from the ASD contributed to the persistent hypoxemia. In light of this, prostacyclin therapy was continued alongside adjunctive vasopressors, resulting in clinical stabilization. The patient was eventually discharged with a treatment regimen that included subcutaneous Treprostinil. Conclusions: It is important to recognize that the consequences of PH are extensive, and that a rare yet significant etiology for persistent hypoxemia may be attributed to right-to-left shunting.