BARCELONA — Patients with type 2 diabetes who have detectable coronary artery disease at diagnosis are at higher risk for cardiac events than are their counterparts in whom there is no evidence of atherosclerosis, Dr. Christoph Säly said at an international congress on prediabetes and the metabolic syndrome.
Current guidelines consider all patients with type 2 diabetes to have equivalent risk for developing a cardiac event. However, existing epidemiologic studies on the risk conferred by type 2 diabetes do not include data on the state of coronary arteries at baseline.
Dr. Säly and his colleagues from the Vorarlberg Institute for Vascular Investigation and Treatment, Feldkirch, Austria, reasoned that because “type 2 diabetes often represents a state of evolving coronary atherosclerosis,” coronary artery disease may be present in many patients but may not yet have caused clinical symptoms, and that this damage may underlie the increased cardiac risk of some patients.
“Previously undiagnosed CAD among patients with diabetes therefore may account largely for their increased cardiovascular risk, which thus is erroneously attributed to diabetes per se,” Dr. Säly said.
To test the effect of CAD on cardiovascular risk in patients with type 2 diabetes, the researchers studied 756 patients who were undergoing coronary angiography for the evaluation of CAD between October 1999 and October 2000. Of the sample, 244 had neither CAD nor type 2 diabetes at baseline, 50 had diabetes with no CAD, 342 had CAD with no diabetes, and 114 had both conditions. Six patients were excluded because they had type 1 diabetes. All study participants were followed for an average of 3.9 years, and cardiovascular events were identified through interviews and patient records.
Event-free survival was significantly lower in patients with both type 2 diabetes and CAD than in all other groups, but patients with type 2 diabetes in whom there was no coronary artery stenoses at baseline survived longer than patients who had CAD but no diabetes. Furthermore, patients with both diabetes and CAD had an event rate of 43%, which was significantly higher than all other groups, and patients with diabetes but no CAD had a significantly lower event rate than did patients with no diabetes but with detectable CAD.
“Type 2 diabetes in the absence of significant coronary stenoses carries a much better prognosis than previously assumed,” said Dr. Säly, adding that as long as the development of significant CAD can be prevented, patients with type 2 diabetes could have much better outcomes.
However, he cautioned, “patients with diabetes who at the baseline angiography of our study did not have significant coronary stenoses of course may develop such stenoses over time and then be at a high risk of vascular events. We therefore intend to perform follow-up examinations over a longer time period.”
The conclusion Dr. Säly and colleagues drew from their work is that “a combination of an angiographic and prospective study thus appears necessary to discern between the risk inherent to diabetes per se and that of evolving atherosclerosis.
“With this approach, the question should be answered whether an increased prevalence of CAD at baseline accounts for the high risk of diabetic patients or, alternatively, whether diabetes per se determines the risk.”