Formerly regarded as an anatomic variant, often found at autopsy and of little or no consequence, PFO is now implicated in the etiology of cryptogenic stroke secondary to paradoxical embolism, platypnea-orthodeoxia syndrome, neurologic decompression illness in scuba divers, and migraine headaches, especially when accompanied with aura.
This reversal of gradient is thought to be responsible for paradoxical embolism in some patients with PFO and normal intracardiac pressures.
16) In most patients, however, determining whether paradoxical embolism has occurred through a PFO requires the presence of the triad of elevated right atrial pressure, a venous source of thrombosis, and a PFO.
26,27) The question whether or not true migraine or migraine-like symptoms are due to transient ischemic attacks or paradoxical embolism is not yet resolved.
Paradoxical embolism via a PFO has been implicated as the most likely mechanism of stroke in cryptogenic stroke/TIA, and therefore, therapeutic measures for secondary prevention are intended to eliminate thrombus formation, paradoxical embolization, or both.
Presence of a postprocedural shunt was predictive of recurrent paradoxical embolism (relative risk 4.
The prevalence of deep venous thrombosis in patients with suspected paradoxical embolism.
The currently available active treatment options for PFO and paradoxical embolism include antiplatelet therapy, anticoagulation, and surgery.
As suggested by Nendaz et al,  surgery is less likely to be beneficial in older patients (age [greater than]50 years) because of the increased likelihood of a false-positive diagnosis of paradoxical embolism and the shorter duration of exposure to complications of life-long systemic anticoagulation.
In contrast, younger patients are at lower risk for anticoagulation complications, but they are exposed to these potential complications for a longer duration, are likely at lower risk during surgical closure of a PFO, and are more likely to have had a true paradoxical embolism as a cause of the cerebral ischemic event.