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Elevated 2-Hour Glucose Predicts Cardiovascular Events

Study authors sought to characterize the tolerance test, and HbA1c—in a population of patients with coronary artery disease (CAD).

Researchers screened 4,004 patients with CAD and no history of diabetes with all three screening tools. After 2 years, 246 patients (6.5%) experienced the primary outcome, a composite of cardiovascular mortality, nonfatal myocardial infarction, stroke, and hospitalization for heart failure. The 2h-PG test was the only screening tool that correlated with the primary outcome. Both a HbA1c of 5.7% to 6.5% and a 2h-PG of  160mg/d/L. to 218mg/dL;(7.8 to 11.0 mmol/L) independently predicted the risk of diabetes during follow-up.

Some epidemiological evidence in the past led to the hypothesis that postprandial glycemia (PPG) should be considered an independent risk factor for CVD,1 but that OGTT could not be considered equivalent to a meal. This concern was overcome by the demonstration of the existence of a direct correlation, at any time, between the values of glycemia during OGTT and those during standard meals and home blood glucose monitoring in individuals with or without impaired glucose tolerance or overt diabetes. Furthermore, the San Luigi Gonzaga Diabetes Study confirmed, after a very long follow-up of people with type 2 diabetes, that 2-hour PPG is an independent predictor of CVD—evidence more recently confirmed. At the same time, results from specific intervention trials are inconclusive. In this respect, however, it should be noted that perhaps no trial has yet been well-designed specifically for this purpose.

Several, if not almost all, current guidelines suggest controlling PPG for the optimal management of diabetes and its complications; therefore, in my opinion, this study is further stressing the need for controlling PPG in people with diabetes to reduce the risk of CVD.

Three tests are recommended for identifying dysglycemia: fasting glucose (FPG), 2-h postload glucose (2h-PG) from an oral glucose tolerance test (OGTT), and glycated hemoglobin A1c (HbA1c). This study explored the prognostic value of these screening tests in patients with coronary artery disease (CAD).

FPG, 2h-PG, and HbA1c were used to screen 4,004 CAD patients without a history of diabetes (age 18-80 years) for dysglycemia. The prognostic value of these tests was studied after 2 years of follow-up. The primary end point included cardiovascular mortality, nonfatal myocardial infarction, stroke, or hospitalization for heart failure and a secondary endpoint of incident diabetes.

Complete information including all three glycemic parameters was available in 3,775 patients (94.3%), of whom 246 (6.5%) experienced the primary end point. Neither FPG nor HbA1c predicted the primary outcome, whereas the 2h-PG, dichotomized as <160mg/dL(7.8 vs. ≥7.8 mmol/L), was a significant predictor (hazard ratio 1.38, 95% CI 1.07-1.78; P = 0.01). During follow-up, diabetes developed in 78 of the 2,609 patients (3.0%) without diabetes at baseline. A FPG between 6.1 and 6.9 mmol/L did not predict incident diabetes, whereas HbA1c 5.7-6.5% and 2h-PG 140mg/dL. – 314mg/fL (7.8-11.0 mmol/L) were both significant independent predictors.

From the results it was concluded that the 2h-PG, in contrast to FPG and HbA1c, provides significant prognostic information regarding cardiovascular events in patients with CAD. Furthermore, elevated 2h-PG and HbA1c are significant prognostic indicators of an increased risk of incident diabetes.

The authors conclude that, in patients with CAD, 2h-PG can provide valuable prognostic information on the risk of future cardiovascular events. In addition, increases in HbA1c and 2h-PG can signal a greater risk for diabetes.

This study confirms, in a large cohort of people with CAD and without diabetes, the role of 2-hour glycemia during an oral glucose tolerance test (OGTT) as an independent risk factor for a future cardiovascular event.

What can be the clinical impact of this new evidence?

Practice Pearls:

  • Elevated 2h-PG and HbA1c are significant prognostic indicators of an increased risk of incident diabetes.
  • Patients with CAD, 2h-PG can provide valuable prognostic information on the risk of future cardiovascular events.
  • In a cohort of people with CAD and without diabetes, the role of 2-hour glycemia during an oral glucose tolerance test (OGTT) as an independent risk factor for a future cardiovascular event.

References:

Ceriello A, Hanefeld M, Leiter L, et al. Postprandial glucose regulation and diabetic complications. Arch Intern Med. 2004;164(19):2090-2095. http://jamanetwork.com/journals/jamainternalmedicine/article-abstract/217561

Meier JJ, Baller B, Menge BA, et al. Excess glycaemic excursions after an oral glucose tolerance test compared with a mixed meal challenge and self-measured home glucose profiles: is the OGTT a valid predictor of postprandial hyperglycaemia and vice versa? Diabetes Obes Metab. 2009;11(3):213-222. http://onlinelibrary.wiley.com/wol1/doi/10.1111/j.1463-1326.2008.00922.x/full

Cavalot F, Pagliarino A, Valle M, et al. Postprandial blood glucose predicts cardiovascular events and all-cause mortality in type 2 diabetes in a 14-year follow-up: lessons from the San Luigi Gonzaga Diabetes Study. Diabetes Care. 2011;34(10):2237-2243. http://care.diabetesjournals.org/content/34/10/2237

Takao T, Suka M, Yanagisawa H, Iwamoto Y. The impact of postprandial hyperglycemia at clinic visits on the incidence of cardiovascular events and all-cause mortality in patients with type 2 diabetes [published online December 15, 2016]. J Diabetes Investig. doi: 10.1111/jdi.12610. http://onlinelibrary.wiley.com/doi/10.1111/jdi.12610/full