Orientation of the Atrial Septum to the Inferior Vena Cava May Contribute to the Persistent Patency of the Foramen Ovale

PURPOSE: There is growing evidence that paradoxical embolism through patent foramen ovale (PFO) is a cause for cryptogenic stroke. However, it is still unclear why the foramen ovale fails to close after birth. We studied whether the 3D relations between the atrial septum (AS) and the inferior vena cava (IVC) are associated with PFO. METHODS: We recruited 30 patients (18-49 years) with a first-ever cryptogenic stroke and 30 age- and sex-matched stroke-free controls. Using cardiac magnetic resonance, an approach to evaluate the 3D relations between the AS and the IVC was developed. The presence of interatrial right-to-left shunt was evaluated with transesophageal echocardiography (TEE) in patients and transcranial Doppler in controls. RESULTS: Of 30 patients, 29 underwent successful TEE, of which 12 (41%) had a shunt. Patients with a shunt had a greater mean 3D angle (γ) between the atrial septal plane and the vector from the orifice of the IVC to the middle of the AS compared with patients without a shunt (45 ± 9° vs. 36 ± 8°, p = 0.017). Of 30 controls, 12 (40%) had a shunt and a greater mean γ compared with controls without a shunt (47 ± 8° vs. 37 ± 10°, p = 0.007). In a pooled analysis, 24 (41%) of 59 subjects with a shunt had a mean γ of 46 ± 9° compared with subjects without a shunt of 37 ± 9° (p < 0.001). CONCLUSIONS: More perpendicular orientation of the atrial septal plane to the orifice of the IVC is associated with PFO, possibly by directing the IVC flow to PFO.