How to understand patent foramen ovale clinical significance: Part I

Patent foramen ovale (PFO) is a remnant of fetal circulation commonly found in healthy population. However, a large number of clinical conditions have been linked to PFO, the most important being ischemic strokes of undetermined cause (cryptogenic strokes) and migraine, especially migraine with aura. Coexistent atrial septal aneurysm, size of PFO, degree of the shunt, shunt at rest, pelvic deep vein thrombosis, and prothrombotic states (G20210A prothrombin gene mutation, Factor V Leiden mutation, MTHFR: C677T, basal homocystine, recent surgery, trauma, or use of contraceptives) could enhance stroke risk in subjects with PFO. Owing to the complexity of this issue, for any individual presenting with a PFO, particularly in the setting of cryptogenic stroke, it is not clear whether the PFO is pathogenically related to the neurological event or an incidental finding. Thus, a heart-brain team, which individually plans the best strategy, in accordance with neuroimaging findings and anatomical characteristics of PFO, is strongly recommended. In the first part of this review, we discuss the embryologic and anatomic features of PFO, the diagnostic techniques for its identification and evaluation, and the relationship between PFO and neurological syndromes. A special attention is made to provide some key points, useful in a daily clinical practice, which summarize how better we understand PFO clinical significance.