months after the operation. Prognosis Many patients with a foramen secundum that persists into adulthood will remain asymptomatic throughout their lives. A mortality rate of less than one tenth of one percent is expected if the operation is performed correctly. Some argue that if the operation is performed before eight years of age, few cardiac abnormalities such as cardiac dysrhythmia are expected later in life. Others argue that the operation can take place as late as age 24, to limit cardiac complications in middle age or later. Some sources have argued that mitral regurgitation and mitral valve prolapse are common after age 40, if the ostium secundum is not repaired by age 24. Operative closure of atrial septal defects after age 40, and the ability to diminish symptoms at all remains controversial. Some data does suggest that even after that age, symptoms can be alleviated via surgical intervention, including prevention of Arrhythmogenic right ventricular dysplasia and other associated cardiac abnormalities. History The discovery of the formation of the foramen secundum and septum secundum was published by P. N. B. Odgers at the University of Oxford in the Journal of Anatomy in 1935. References External links http://www.mayoclinic.org/atrial-septal-defect/types.html http://staff.um.edu.mt/acus1/Heart-b.htm Embryology of cardiovascular system