EFFECT OF AUTONOMIC NERVOUS-SYSTEM DYSFUNCTION ON THE CIRCADIAN PATTERN OF MYOCARDIAL-ISCHEMIA IN DIABETES-MELLITUS

Objectives. The aim of this study was to determine the prevalence and characteristics of ambulatory myocardial ischemia in patients with dia betes mellitus and to delineate the relation between the presence and severity of autonomic nervous system dysfunction and the incidence and time of onset of myocardial ischemia. Background. Conflicting data ex ist with regard to the circadian pattern of myocardial infarction and other cardiovascular events, such as ambulatory ischemia, in diabetes. Methods. We performed ambulatory electrocardiographic monitoring in 6 0 patients with diabetes and coronary artery disease. Autonomic nervou s system testing was performed in a subgroup of 25 patients with myoca rdial ischemia after discontinuation of all antianginal medications. R esults. Thirty-eight of 60 patients had evidence of ambulatory ischemi a; 91% of all ischemic episodes were asymptomatic. The 25 patients wit h ambulatory ischemia who underwent autonomic nervous system testing h ad a peak incidence of ischemia between 6 AM and noon (46 of 133 ische mic episodes, p < 0.007), compared with the other three 6-h periods. F ifteen of the 25 patients had no or mild autonomic nervous system dysf unction and demonstrated a similar peak incidence of ischemia between 6 AM and noon (p 0.0009). However, the 10 patients with moderate to se vere autonomic nervous system dysfunction did not experience a morning peak of ischemia, and the number of ischemic episodes was distributed evenly throughout the day (p = 0.4). Conclusions. Silent ischemia is highly prevalent among patients with diabetes and coronary artery dise ase. Time of onset of ischemia in diabetic patients follows a circadia n distribution, with a peak incidence in the morning hours. However, p atients with significant autonomic nervous system dysfunction did not demonstrate such a peak, suggesting that alterations in sympathovagal balance may have an effect on the circadian pattern of cardiovascular events.