Strict glycaemic control is strongly advocated in people with type 2 diabetes to prevent vascular disease. However, the outcomes of two large clinical trials have indicated the potential dangers of pursuing this policy in those at high risk of cardiovascular disease, with an excess of fatal vascular events being associated with a higher frequency of severe hypoglycaemia. Hypoglycaemia secondary to insulin and sulphonylurea therapy is often associated with serious morbidity; anecdotal evidence has long implicated hypoglycaemia as a potential cause of myocardial ischaemia or a cardiac arrhythmia. Hypoglycaemia provokes sympatho-adrenal activation and counterregulatory hormone secretion, which exert pronounced cardiovascular effects. Although well tolerated in healthy people, the superimposition of these profound physiological effects on a diseased coronary vasculature and a dysfunctional cardiac conductive system may induce serious or even fatal cardiovascular events. These risks should influence therapeutic targets and the approach to diabetes management in people with diabetes with established vascular disease in whom exposure to severe hypoglycaemia could be dangerous.
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