Complete situs inversus is a rare syndrome, with overall frequency estimated at 1/10,000 births, resulting from abnormal rotation of the cardiac tube during embryogenesis, of unknown mechanism. Recent studies suggest that left-right asymmetry defects are likely to be due to genetic abnormalities in the lefty, nodal, i.v., HAND, ZIC3, Shh, ACVR2B and/or Pitxz genes. In dextrocardia with situs inversus the heart is structurally normal in 90-95% of cases, in contrast to dextroversion (dextrocardia with situs solitus), which has a high incidence of structural cardiac defects. Atrial septal defect is one of the most common congenital cardiac anomalies in adults. Diagnosis is based on clinical manifestations and simple complementary diagnostic exams like abdominal and thoracic radiography and electrocardiogram. Prognosis in isolated dextrocardia depends on the congenital cardiac defects present. By contrast, in dextrocardia with situs inversus life expectancy is similar to that of the general population. The authors present the case of a 64-year-old German man admitted to the emergency care unit with a diagnosis of embolic stroke due to atrial fibrillation with fast ventricular rate. As clinical history could not be assessed due to language limitations, routine admission tests were performed. They revealed complete situs inversus with corrected ostium secundum atrial septal defect. Finally, the anatomic, pathologic, embryologic and etiologic features of complete situs inversus and related abnormalities of the cardiac structures are presented. Special emphasis is given to genetic abnormalities, the study of which has seen great advances since the 1990s thanks to new techniques of DNA analysis.