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A 33 year old woman on the oral contraceptive pill was investigated after suffering a transient ischaemic attack. On transthoracic echocardiogram her interatrial septum was mobile but not aneurysmal. On transoesophageal echocardiography there was no clear anatomical evidence of a septal defect or patent foramen ovale (PFO). Several agitated saline contrast studies via the right cephalic vein failed to show any evidence of an intracardiac shunt both with and without a Valsalva manoeuvre (below left). This was then repeated via a right femoral vein 5 French sheath and there was notable and immediate passage of contrast into the left atrium, even without a Valsalva manoeuvre (below right).
Paradoxical embolus via a PFO is a potential cause of cerebrovascular events in a young patient. Diagnostic methods include transthoracic and transoesophageal echocardiography with colour Doppler and agitated saline contrast studies. Sensitivity may be further enhanced by cough and the Valsalva manoeuvre. Transcranial Doppler of the middle cerebral artery may also be used. Inferior vena caval flow is preferentially towards the interatrial septum and foramen ovale while the crista interveniens directs superior vena cava flow away from the interatrial septum. Thus, because of this “streaming” effect, femoral vein delivery of agitated saline contrast may be superior to the antecubital route for detection of transient right to left shunting through a PFO.