Glycemic Variability vs. A1c on Major Adverse Cardiac Events

Just how important is glycemic variability?…

Dysglycemia is associated with poorer prognosis in patients with acute myocardial infarction (AMI). Whether admission glycemic variability (GV) has important value in prognosis of AMI patients is still unknown. The aim of this study is to investigate the prognostic value of admission GV, glucose, and glycosylated HbA1c in AMI patients. 

We measured blood glucose, HbA1c, and GV on admission in 222 consecutive patients with diagnosed AMI. GV, indicated as the mean amplitude of glycemic excursions (MAGE), was determined by a continuous glucose-monitoring system. MAGE was categorized as >3.9 or <3.9 mmol/L; admission glucose as <8.61 or >8.61 mmol/L; and HbA1c as >6.5 or <6.5%.

Participants were followed up prospectively for 12 months. The relationship of admission MAGE, glucose, and HbA1c to the major adverse cardiac event (MACE) of AMI patients was analyzed.

In 222 enrolled patients with AMI, the rate of MACE by MAGE category (<3.9 or >3.9 mmol/L) was 8.4 and 24.1%, respectively (P = 0.001), by admission glucose category (<8.61 or >8.61 mmol/L) was 10.1 and 21.6%, respectively (P = 0.020), and by HbA1c category (<6.5 vs.>6.5%) was 10.7 versus 18.7%, respectively (P = 0.091). In multivariate analysis, high MAGE level was significantly associated with incidence of MACE (hazard ratio 2.419 [95% CI 1.273–9.100]; P = 0.017) even after adjusting for Global Registry of Acute Coronary Events risk score, but admission glucose and HbA1c was not.

More and more evidences have been found that glycemic variability may be an important role in resolving potential vascular problems in diabetes. Some researchers suggested that post-challenge glucose excursion is independently related to carotid intima-media thickness and may contribute to the development of atherosclerosis in individuals with T2DM independent of other risk factors. In our previous study, we found that GV is an important contributing factor in the severity of CAD, which is independent of the average level of blood glucose.

The Verona Diabetes study reported that fasting GV is an independent predictor of mortality in T2DM patients. Some studies concluded that GV was a significant predictor of mortality in critically ill patients independently from mean glucose level and severity of illness. In the current study, patients with a higher MAGE level (>3.9 mmol/L) have higher GRACE risk scores. After 1-year follow-up, a significantly higher incidence of MACEs and cardiac mortality was found in those patients. The results indicate that high glucose fluctuations may be associated with the risk of future adverse cardiovascular events in patients with AMI. Multivariate analysis disclosed that in the AMI population, GV (i.e., MAGE>3.9mmol/L) was an independent predictor of MACEs, even after adjusting for GRACE risk score.

In conclusion elevated admission glycemic variability appears more important than admission glucose and prior long-term abnormal glycometabolic status in predicting 1-year MACE in patients with AMI.

Diabetes Care Publish Ahead of Print, published online January 24, 2013