Sudden and unexpected non-traumatic deaths in adults: a review of epidemiological and clinical studies.

Abstract The reported studies of sudden and unexpected non-traumatic deaths in adult populations have been reviewed. The percentage of deaths certified by a Coroner or Medical Examiner is the only available measure of the frequency of sudden death in a community. The problems associated with the use of only Medical Examiners' certified deaths were discussed. The greater frequency of sudden deaths observed in certain ethnic, racial and economic groups may well be due to differences in the availability of medical care which influence the frequency of certification by the Medical Examiner. Although there are many possible causes of sudden death, cardiovascular disease, especially coronary artery disease, accounts for the majority of cases. Several prospective and cross-sectional studies of coronary artery disease were reviewed in order to obtain some measure of the incidence of sudden death as the first and only manifestation of coronary artery disease. Almost all of these studies have reported that about 20 per cent of new coronary events are sudden deaths. Furthermore, longitudinal studies of individuals who have survived the immediate period following a myocardial infarction have also reported a high risk of sudden death among the original survivors. Many of the studies have shown that the immediate mortality rate following a myocardial infarction is greater than the rate during the next 5 years among those who have survived the first 24 hr after their infarction. Whether or not individuals who die suddenly following a new coronary event differ in certain biological or social characteristics which affect their probability of survival is unknown. Very limited data have suggested that sudden death may be more common in the young and in men [20, 32]. Their blood pressure, cholesterol and body weight prior to death appear to be similar to those who have survived, but the available data are extremely limited [40]. The relationship of physical activity at the onset of a new coronary event and prior occupation to the likelihood of sudden death has not been studied adequately and no definite data are available. The pathophysiology of sudden and unexpected death has been difficult to study. The use of animals as models for the study of the various pathophysiological events in man has been questioned by several investigators. Because of the large number of deaths that occur outside of a hospital and are frequently medically unattended, the mechanisms of death have not been determined. Many studies are under way which are attempting to delineate the pathophysiology of various arrhythmias and the mechanisms of shock following a myocardial infarction. New techniques of monitoring the electrocardiogram have made it possible to measure the types and frequency of various cardiac arrhythmias following a myocardial infarction. It also appears possible to monitor the daily activities of normal men and obtain some estimate of the frequency and types of arrhythmias that occur during regular activities. A high risk group of individuals may exist who develop recurrent arrhythmias following a variety of activities, ultimately leading to ventricular fibrillation, asystole and death. Several other diseases which may cause sudden death were discussed. These diseases can be broadly classified into two groups: (1) rare diseases which are often associated with sudden death; and (2) relatively common diseases, in which a small proportion of all deaths are sudden. In the first group are several cardiovascular diseases such as ruptured and dissecting aneurysms, while in the second group are a variety of diseases such as rheumatic heart disease, cerebrovascular disease, and cirrhosis of the liver. Neither adequate cross-sectional studies nor longitudinal studies have been carried out on any of these diseases, so the frequency of sudden death and the characteristics of the victims are as yet undetermined. It is unfortunate that most studies of cardiovascular diseases are restricted either to cases admitted to a hospital, cases seen by a physician in consultation, or to deaths certified by the Medical Examiner. It is obvious that in order to obtain a true picture of cardiovascular mortality in a community, the deaths at home and those certified by the Medical Examiner must be studied as diligently as the hospital cases. The prospective and cross-sectional epidemiological studies of coronary artery disease are frequently limited to homogenous groups, most often middle class white males. They are further limited to a relatively small number of new cases. Only a few studies have attempted to analyse cardiovascular disease in negroes or in women. Because of the large number of deaths attributed to cardiovascular disease certified by the Medical Examiner or Coroner, variations in methods of certification can significantly affect death rates from some cardiovascular diseases. Whether variations in the frequency of attributing sudden death to ASHD accounts for observed geographical differences in mortality rates, needs to be determined. Studies of the relationship of sudden deaths to variables known to increase the risk of coronary artery disease should be analyzed. Finally, the place of occurrence, activity at onset, prior symptomology and medical care, and availability and utilization of emergency facilities in a community should be studied in order to adequately plan the development of intensive care and other facilities in communities.