Pharmacologic exposure of an occult atrial septal defect.
Mackenzie IM., Banning A., Dyar O.
OBJECTIVE: To describe the diagnostic technique used to identify the presence of a symptomatic interatrial shunt obscured by normal intracardiac pressures and to discuss the unusual findings in this case and their relevance to the investigation of patients with unexplained hypoxemia. DESIGN: Case report. SETTING: Intensive care unit of a university teaching hospital. PATIENT: A patient with a variant of the platypnea-orthodeoxia syndrome. INTERVENTIONS: Intravenous administration of metaraminol. MEASUREMENTS AND MAIN RESULTS: Clinical examination and routine investigations ruled out pneumonia or myocardial infarction as a cause of respiratory failure, and pulmonary angiography was normal other than for the demonstration of an interatrial communication. Repeated transthoracic echocardiograms failed to indicate the presence of a significant interatrial shunt that was eventually detected following temporary shunt reversal with intravenous metaraminol and confirmation by bubble-contrast transesophageal echocardiography and right heart catheter studies. CONCLUSIONS: Symptomatic right-to-left intracardiac shunt may occur in patients with normal intracardiac and pulmonary artery pressures. The presence of a significant shunt cannot be ruled out by transthoracic echocardiography without the use of bubble contrast.