Three-dimensional and catheter-based intracardiac echocardiographic characterization of the interatrial septum in 2 horses with suspicion of a patent foramen ovale.
Authors: Vernemmen Ingrid, Paulussen Ellen, Dauvillier Julie, Decloedt Annelies, van Loon Gunther
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Patent foramen ovale (PFO) in horses presents a diagnostic challenge, as anatomical variants of the fossa ovalis can mimic pathological shunting on standard two-dimensional transthoracic echocardiography (2D-TTE). Vernemmen and colleagues used complementary imaging modalities—2D-TTE, three-dimensional transthoracic echocardiography (3D-TTE), and intracardiac echocardiography (ICE)—to characterise the interatrial septum in two horses: one with poor performance and an apparent septal defect, and another presenting with a cardiac murmur and colour flow Doppler evidence of abnormal flow. The first case demonstrated how 3D-TTE and ICE can differentiate a benign deepened fossa ovalis from a true PFO with haemodynamic shunting, whilst the second case confirmed an actual left-to-right PFO with flow direction from dorsocranial to ventrocaudal but limited clinical significance. These findings establish ICE as a valuable adjunctive tool for definitive diagnosis when standard echocardiography raises suspicion of interatrial shunting, potentially avoiding misdiagnosis in horses presenting with non-specific poor performance or incidental murmurs and preventing unnecessary treatment of clinically insignificant lesions.
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Practical Takeaways
- •When evaluating horses with poor performance or cardiac murmurs, anechoic zones in the interatrial septum on standard ultrasound may represent anatomical variants rather than pathological shunts—3D and ICE imaging can provide definitive characterization
- •ICE is a feasible and valuable clinical tool in equine practice for detailed assessment of cardiac structures and hemodynamic flow patterns when transthoracic imaging is inconclusive
- •A patent foramen ovale with left-to-right shunt may not always have significant clinical implications; detailed imaging helps determine hemodynamic significance and guide clinical decision-making
Key Findings
- •3D-TTE successfully identified a deepened fossa ovalis in the first case, which was distinguished from a true patent foramen ovale using ICE
- •ICE excluded the presence of an interatrial shunt in the first case despite an anechoic zone visible on 2D-TTE
- •The second case demonstrated a patent foramen ovale with left-to-right shunt in a dorsocranial to ventrocaudal direction with limited hemodynamic consequences
- •Intracardiac echocardiography provided superior diagnostic clarity compared to 2D and 3D transthoracic echocardiography for characterizing the interatrial septum