Part II - Decompression sickness, migraine, arterial deoxygenation syndromes Patent foramen ovale (PFO) is frequently identified in young patients with cryptogenic ischaemic stroke.The following are key perspectives from the European position paper on the management of patients with patent foramen ovale (PFO). As the heart develops in the foetus, the primum and secundum septa grow and overlap. At birth, the PFO should close. Recent randomized trials have confirmed the role of patent foramen ovale (PFO) closure in the secondary prevention of cryptogenic stroke.