The foramen ovale is an ellipsoidal-shaped tunnel in the interatrial septum of the foetal heart allowing a rightto- left shunt between the two atria. It generally closes soon after birth but remains permeable in about 30% of adults. The frequency of this patent foramen ovale (PFO) in stroke patients is higher than among the general population, particularly in individuals with stroke of unknown aetiology (cryptogenic stroke) and in younger patients. Three theories have been proposed to explain the role of PFO in cryptogenic stroke: the paradoxical embolism theory, the arrhythmogenic theory and the thrombogenic theory. None have as yet been irrefutably confirmed. However, several secondary stroke prevention strategies have been developed in these patients: antiplatelet agents, oral anticoagulants, percutaneous closure and surgical repair. Secondary stroke prevention in these patients is presently one of the most controversial issues among cerebrovascular disease experts. We present a state-of-the-art review of secondary stroke prevention evidence in patients with cryptogenic stroke and PFO.
Keywords: Patent foramen ovale, cryptogenic stroke, paradoxical embolism, atrial septal aneurysm, transcranial Doppler, transesophageal echocardiography, percutaneous closure