Real-world experience of transoesophageal echocardiography for detection of clinically significant persistent foramen ovale

Introduction: Transoesophageal echocardiography (TOE) is claimed to be the investigation of choice for detecting a persistent foramen ovale (PFO) with almost 100% diagnostic accuracy. If true, TOE would detect all large/clinically significant PFOs. Methods: Retrospective analysis to determine the sensitivity of TOE for detection of clinically significant PFOs. Patients were from a consecutive series of 150 patients who had transcatheter closure of a PFO following events attributed to paradoxical embolism (decompression sickness or stroke). In each patient, transthoracic echocardiogram with bubble contrast showed a clinically significant atrial right-to-left shunt. The data reported are from the sub-group of the 150 patients with a clinically significant PFO who also had a TOE performed in other hospitals. Results: Twenty seven of 150 consecutive patients had a total of 31 TOEs performed at 22 United Kingdom regional cardiac centres. TOE failed to detect a PFO in 17 of the 27 patients. Four patients had a TOE on two separate occasions and in each case both of the TOEs failed to show a PFO. TOE gave a false negative test in 21 of 31 investigations (sensitivity 32%). The mean PFO diameter was 9.4 mm (median 9 mm, range 5-16 mm) in the 21 patients in whom balloon sizing was performed and 9.8 mm (median 10 mm, range 5-16 mm) in the 13 patients in whom balloon sizing was performed and a TOE failed to show a PFO. Conclusions: These finding demonstrate that the precision of TOE for detecting a PFO in real world clinical practice is considerably lower than generally believed.