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Pharmacologic exposure of an occult atrial septal defect

Mackenzie, Iain M. DM, MRCP, FRCA; Banning, Adrian MD, MRCP; Dyar, Oliver MRCPI, FRCA

Case Reports

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.

From the Nuffield Department of Anaesthetics (IMM, OD) and the Department of Cardiology (AB), John Radcliffe Hospital, Oxford, UK.

Performed in the Intensive Care Unit, John Radcliffe Hospital, Oxford, UK.

The presence of a significant shunt cannot be ruled out by transthoracic echocardiography without the use of bubble contrast.

© 2001 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins