Patent foramen ovale and stroke: what we do and don't know.

Paradoxical embolism through a patent foramen ovale (PFO) is a commonly identified mechanism of ischemic stroke, especially in young patients. The ability to detect PFOs in life improved dramatically with the development of aerated ultrasound contrast, transesophageal echocardiography, and transcranial Doppler ultrasound. Similarly, the ability to detect source venous thromboemboli is improving with pelvic magnetic resonance venography. Coexisting atrial septal aneurysm is the only definite potentiator of stroke risk in patients with PFO. PFO size and degree of functional shunting may be additional risk factors. Currently, PFOs are treated variably with antiplatelet agents, anticoagulants, surgical closure, or, increasingly, percutaneous closure devices. Completion of randomized clinical trials is urgently needed to clarify if the risks of invasive endovascular device placement are outweighed by a long-term reduction in recurrent vascular events.