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Figure 3 Transverse section on the aortic valve plane (A), and longitudinal section on the four-chamber plane (B) in a patient with secundum atrial septal defect (ASD). The major and minor axes of the fossa ovalis can be accurately evaluated by intracardiac echocardiography (ICE): a = 9.8 mm and b = 9.3 mm. The r value is computed as follows: c = 9.8² – 9.3² = 3.090 mm, p =

= 8.825 mm, r = 3.090² + 8.825² = 9.35 mm, where c is the foci half-distance, p is the semi-latus rectum distance, and r is the estimated radius of the ICE-derived Amplatzer Septal Occluder (ASO). In this case, we implanted a 19-mm ASO. AoD = descending aorta; LA = left atrium; MV = mitral valve; RA = right atrium; RUPV = right upper pulmonary vein; TV = tricuspid valve.