OBJECTIVETo identify the epidemiological and clinical features of unexpected sudden cardiac deaths (SUD) in Yunnan.

METHODSChoosing the old SUD cases from Xiangyun, Heqing, Nanjian and Dayao counties and using the standardized verbal autopsy Form, we interviewed the family members of the cases, witnesses and doctors as well as reviewing their medical files to get relative information.

RESULTSWe identified 116 SUDs in 21 villages from 1984 to 2004. The village-specific annually standardized incidence rates were ranged from 0.2/1000 to 8.9/1000 (median = 0.8/1000). 66% and 29% of the SUDs occurred in July and August respectively. The incidence rates of SUD were higher (1.6/1000, chi(2) = 16, P < 0.01) in 10 - 39 year-olds, and higher in females than in males (RR = 1.6, 95% CI: 1.1 - 2.3). Seventy percent of SUD occurred in families having clustering nature and 60% of the additional cases in the family were occurred within 24 hours (median = 20 hours) after the first SUD identified in the family. SUD occurred in 23 families followed the first affected family in a village during the same season. In these 23 families, 61% of the first SUD occurred within 8 days after the first SUD in the first affected family. 68% and 66% of the SUDs did not have any complaints or signs during the last 3 weeks or from 3 weeks to 2 days prior to the onset of the disease. 63% of the SUDs had cardiac symptoms within the last 2 days prior to the onset with major symptoms as dizziness, nausea, faintness, unconsciousness, weakness and palpitation. The median duration from acute onset to death was 2 hours.

CONCLUSIONSThe extreme time-space clustering of SUD in families and in villages suggested that the risk factors occurred in specific time and location. Familial clustered SUD cases had common exposure pattern. Sudden onset of acute cardiac symptoms often followed by sudden death. Epidemiological study on new cases was necessary to identify risk factors and to develop hypothesis for causation. In July 2005, we instituted a special SUD surveillance system for all the affected counties together with 10 counties which had no reported cases.