Funnel-type patent foramen ovale morphology on 3D echocardiography: a novel high-risk anatomic feature

Cryptogenic strokes are associated with patent foramen ovale (PFO), but accurate risk assessment remains difficult. To better identify clinical and anatomical high-risk profiles, we describe a morphological classification of PFO using 3D transoesophageal echocardiography (TEE).

3D-TEE was performed in 95 consecutive patients with a right-to-left shunt. A classification was made based on the internal geometry: 'cone type' (wider left atrial end) and 'funnel type' (wider right atrial [RA] end). Morphology was related to the clinical history of ischaemic stroke or transient ischaemic attack (events). Thirty-seven (38.9%) had prior events. This group had a larger cross-sectional area of the RA opening (48.5 [18.4-67.0] vs. 11.75 [8.6-17.9] mm2, P = 0.002). Funnel morphology was more common in the event group (81.1% vs. 50%, P = 0.001) and was associated with more than twice the rate of events than cone morphology (50.8% vs. 19.4%, P = 0.002). On multivariable analysis, dyslipidaemia (odds ratio [OR] 21.06), smoking (OR 6.25), funnel morphology (OR 6.47), and a larger RA opening area (OR 1.026 per mm2) were independent predictors of events. Receiver operating characteristic analysis identified an RA opening area >15.85 mm2 as the optimal cut-off to predict events (area under the curve 0.719).

Prior events are highly correlated with funnel-type PFO, particularly when RA opening area exceeds 15.85 mm2. This geometry may act as an embolic 'catchment' and favour in situ thrombosis due to disturbed flow from the wide RA inlet to the narrow tunnel exit. Integration of 3D-TEE morphology with systemic risk factors such as smoking and dyslipidaemia may refine patient stratification and guide management.