Background: Incidence of patent foramen ovale (PFO) has been estimated at 25% in the general population and 6% for larger defects. Data on the relationship between PFO morphology and the risk of stroke are limited. PFO closure has become a common practice in many centres, although recent guidelines limit indications for such treatment to patients with cryptogenic (recurrent) stroke.
Aim: To investigate whether PFO morphology assessed by transoesophageal echocardiography (TOE) differed between patients with symptoms and those who had an asymptomatic PFO.
Methods: We analysed 88 consecutive patients (48 female, 40 male; mean age 36.1 ± 16.2 [range 18–59] years) who underwent TOE before transcatheter PFO closure due to a cryptogenic cerebrovascular event (Group I) and compared them to 88 consecutive patients (49 female, 39 male; mean age 35.7 ± 14.2 [range 18–57] years) with an asymptomatic PFO found incidentally on TOE (Group II). The diagnosis of stroke was based on the occurrence of a new acute focal neurological deficit, with neurological signs and symptoms persisting for > 24 h, subsequently confirmed by computed tomography and/or magnetic resonance imaging. Multiplane TOE was conducted as per guidelines using commercially available instruments. The interatrial septum was viewed in the transverse midoesophageal 4-chamber view and the longitudinal biatrial-bicaval view. PFO was diagnosed with intravenous injections of agitated saline while the patient was at rest and during the Valsalva manoeuvre. We analysed PFO size (resting and maximal separation of the septum primum and secundum during the Valsalva manoeuvre), tunnel length (maximal overlap of the septum primum and secundum), presence of an atrial septal aneurysm (excursion > 15 mm), shunt severity (mild: 3–5, moderate: 6–25, severe > 25 microbubbles) and prominence of the Eustachian valve.
Results: The two groups did not differ with respect to age and sex distribution. Group I showed larger PFO size (maximal separation 3.9 ± 1.4 vs. 1.3 ± 1.3 mm, p < 0.0001), longer tunnel length (14 ± 6 vs. 12 ± 5.5 mm, p < 0.05) and a greater frequency of atrial septal aneurysm (55% vs. 15%, p < 0.0001) compared to Group II (controls). Group I was also characterised by a higher proportion of large PFOs (≤ 4 mm; 50% vs. 18%, p < 0.001) and severe shunt (40% vs. 2%, p < 0.0001).
Conclusions: PFO in symptomatic patients is larger in size, has a longer tunnel and is more frequently associated with atrial septal aneurysm. Asymptomatic patients with PFO characteristics similar to that seen in stroke patients require more careful clinical evaluation. It may be debated whether such patients should be recruited to prospective trials to evaluate indications for PFO closure in stroke prevention.