PFO assessment and closure for the general physician

A quarter of adults have a persistent (patent) foramen ovale (PFO). Right-to-left shunting through a PFO can facilitate paradoxical thromboembolism, cryptogenic stroke, paradoxical gas embolism, decompression sickness, arterial hypoxaemia and migraine with aura. Atrial septal defects and pulmonary shunts are also associated with these diseases, and investigation must differentiate them from a PFO. The detection and assessment of PFOs and other right-to-left shunts uses ultrasound techniques augmented with intravenous injection of bubble contrast. When diseases are attributed to a PFO, the PFO is usually large, typically about 10 mm diameter and associated with a large right-to-left shunt. Transcatheter closure of a PFO is relatively simple, but it is not always effective. Therefore patients require careful pre-procedure counselling about risks, benefits, success rates and alternative treatments.