Sudden death from non-traumatic right atrial appendage rupture: an autopsy case.

Myocardial rupture most often involves the ventricles following acute myocardial infarction, whereas non-traumatic atrial rupture is extremely uncommon, and typically confirmed histologically. Isolated atrial infarction is rare and diagnostically challenging, requiring careful distinction from traumatic causes in forensic practice. We report a fatal case of non-traumatic rupture of the right atrial appendage (RAA). The patient was a 43-year-old woman with systemic lupus erythematosus. Postmortem computed tomography revealed high-density areas within the pericardial space. Autopsy demonstrated a 250 mL pericardial hematoma. The rupture site was identified at the apex of the RAA, located directly above the tricuspid valve in the inflow tract of the right atrial vestibule. Localized hemorrhage was present around the rupture site, and thrombus attachment was observed at this location. Histological examination of the RAA revealed wavy myocardial fibers with early coagulative necrosis surrounding the rupture site. Some fibers exhibited eosinophilia, thinning, loss of striation, and band necrosis. The right coronary artery adjacent to the rupture site showed atherosclerotic stenosis with a platelet thrombus. Based on these findings, the cause of death was determined to be endogenous rupture of the RAA secondary to atrial infarction. Although non-traumatic rupture of the RAA is extremely rare, distinguishing it from traumatic rupture in forensic practice is critically important and requires recognition of its characteristic histological features.