Abstract 12858: Relationship of Patent Foramen Ovale Morphology and Shunt Size: Insights from 3D Transoesophageal Echocardiography

Abstract

Background Patent foramen ovale (PFO) is implicated in paradoxical embolism and stroke. The relationship between anatomy, right-to-left shunt and embolic risk is unclear. Certain anatomical features may identify those most likely to benefit from device closure. 3D TEE has enabled better imaging of atrial septal anatomy and PFO morphology with delineation of structures not previously appreciated. The functional implications of PFO morphology is not known. We examined the relationship between the PFO on 3D TEE and degree of left-to-right shunting.

Method Transthoracic saline bubble studies and 3D TEE datasets were analysed in 33 patients, with otherwise structurally normal hearts, considered for PFO closure. The shunt was classified based on the number of bubbles per still frame in the left heart within 3 cardiac cycles. 3D ‘zoom mode’ datasets (Philips iE33) were assessed offline (QLab 3DQ) for anatomical characteristics including: PFO and atrial septal dimensions, atrial septal mobility and other lesions such as hybrid defect, Eustachian ridge (ER), valve or Chiari network.

Results Shunt size was classified as small/moderate (<25 bubbles n=8), large (25-50 n=12) or very large (>50 n=13). There was no association between the right-to-left shunt and anatomical features of the PFO or fossa dimensions, although there was a trend towards greater shunting in those with greater dimensions (figure). Other features including presence of a Eustachian valve, ridge, Chiari network or hybrid defect were not associated with the degree of shunting. Similarly, the number of complex anatomical features associated with a PFO do not appear relate to the magnitude of the shunt.

Conclusions The morphological characteristics of a PFO are a relatively poor guide to the magnitude of the right-to-left shunt. Factors influencing shunting are complex, and the relationship between the anatomical defect, shunt and clinical risk requires further study.