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.