ABSTRACT
ETIOLOGY A patent foramen ovale (PFO) develops when fibrous adhesions fail to seal the atrial septum after birth, allowing the persistence of a potential shunt between the right and left atria of the heart. This is a common finding in the general population but the finding of increased incidence in patients with stroke, particularly those with cryptogenic stroke, has led to the suggestion that PFO may be a risk factor for stroke. This in turn has resulted in PFO closure being proposed as a treatment to prevent stroke. Whether this is an appropriate treatment can only be answered by large randomized trials which are in progress. However, there is already considerable data on the association between PFO and stroke which will be reviewed in this chapter. This will be considered under a number of headings:
1. Epidemiological studies determining the relative prevalence of PFO in stroke patients compared with controls.
