[Sudden death of clinically unknown origin. An overview of postmortem examinations in Japan]

To elucidate the possible causes of sudden unexpected deaths (SUD) in Japan, we over-viewed autopsy findings described in the Annual of the Pathological Autopsy Cases in Japan, Vol. 35-37, 1992-1994. A total of 313 cases of SUD of clinically unknown origin (age > = 5 year) were found among the 95,142 autopsy cases listed in the above compilation. The direct causes of death, if identified, were described with their incidences. When the direct cause was undetermined, the most dominant pathological finding was listed. The difference in age between identified and unidentified groups was also studied. In 225 (72%) out of 313 SUD, direct causes of death were clarified as follows: cardiovascular diseases in 140 (acute myocardial infarction in 75), pulmonary diseases in 32, cerebrovascular diseases in 17, and gastrointestinal or hepatic disease in 17 cases. Even among 88 cases whose direct causes of death were unclear, 55 had cardiovascular abnormalities including myocardial hypertrophy and ischemic changes. No life-threatening abnormalities were found in 23 SUD cases, most of whom were men in their forties or younger. This study indicates that autopsy is helpful to reveal the cause of SUD. It also suggests cardiovascular diseases are the leading causes of SUD of clinically unknown origin.