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In cryptogenic stroke and patent foramen ovale (PFO) multiple ischaemic strokes or transient ischaemic attacks (TIA) before diagnosis predispose to recurrent strokes later, Nedeltchev et al have found. Whether PFO causes cryptogenic stroke—through embolism of a venous clot across the atrial right to left shunt—is debatable, though meta-analysis suggests that it does. Also, in the absence of controlled trials there is no consensus about which patients with PFO are at risk of stroke, how many recurrences they might have, and suitable treatment.
Nedeltchev et al believe that careful observational studies might help to answer these questions and followed up 159 patients with cryptogenic stroke and PFO opting for medical treatment—oral anticoagulants (79) or platelet inhibitors (80).
In three quarters of the patients the event leading to diagnosis of PFO was an ischaemic stroke; the rest were TIA (24%) and amaurosis fugax (1%). The average annual rate of recurrent strokes and recurrent strokes or TIAs measured over a mean of 29 months rose—from 1.8% to 3.6% and 5.5% to 9.9%, respectively—when patients with multiple ischaemic events before diagnosis of PFO were analysed separately. A log rank test on survival data confirmed that patients with multiple events were significantly more at risk of later recurrences than those whose first event prompted the diagnosis. Recurrence rates were comparable to those of previous studies, but neither treatment seemed better than the other.
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