Physicians' Academy for Cardiovascular Education

Hyperglycaemia appears harmful to the myocardium, also in prediabetics

Selvin E et al., Circulation. 2014

 
Diabetes Mellitus, Prediabetes, and Incidence of Subclinical Myocardial Damage

 
Selvin E, Lazo M, Chen Y, et al.
Circulation. 2014;130:1374-1382. doi: 10.1161/CIRCULATIONAHA.114.010815
 

Background

Evidence exists that at the time of clinical diagnosis of diabetes mellitus (DM), there is often already cardiac damage [1,2]. Also if people do not meet diagnostic criteria yet for DM, hyperglycaemia is thought to induce coronary microvascular dysfunction [3-8], resulting in myocardial injury and putting people at risk for cardiovascular events. Persons with prediabetes or DM have been shown to have an increased prevalence of atherosclerosis, as measured by carotid intimal thickness or coronary artery calcium [8-13].
The relationship between prediabetes or DM and subclinical myocardial damage is less clear. A novel high-sensitivity assay for cardiac troponin T (hs-cTnT) is available which allows for the reliable measurement of troponin for diagnostic purposes [14]. Cardiac troponin detected with this assay in asymptomatic persons may represent chronic subclinical myocardial injury, of a nonatherosclerotic origin [15,16], and was strongly associated with subsequent heart failure and death, but only moderately with risk of coronary heart disease [17].
This study set out to characterise the association of DM (HbA1c >6.5%) and prediabetes (HbA1c of 5.7% to 6.4%) with 6-year incidence of subclinical myocardial injury (assessed by hs-cTnT), in a community-based population (ARIC study), without a clinical history of CV disease.

 
Main results

  • Diabetes status at baseline was strongly associated with higher levels of hs-cTnT, such that in those with DM, 15.3% had hs-cTnT of 9-13 ng/L, while only 6.2% of people without diabetes this was seen.
  • The risk of CV events or death was significantly associated with incident subclinical myocardial damage (incident hs-cTnT > 14 ng/L), even after adjustment for CV risk factors. Persons with prediabetes or DM had a higher risk than patients without DM at visit 2, after about 3-4 years (HR: 1.40, 95%CI: 1.08-1.80 and HR: 2.47, 95%CI: 1.78-3.43 respectively).
  • Persons with incident elevated hs-cTnT and DM had substantially increased risks of heart failure (HR: 6.37, 95% CI: 4.27–9.51), all-cause mortality (HR: 4.36, 95%CI: 3.14–6.07), and coronary heart disease (HR: 3.84, 95% CI: 2.52–5.84) compared with those with no incident elevations in hs-cTnT and without DM.
  • Similar results were seen when data were analysed for black and white people separately.
  • Adding hs-cTnT to prediction models significantly improved model discrimination for heart failure and death.

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Conclusion

This study provides evidence for a harmful effect of hyperglycaemia on the myocardium, even if patients do not meet diagnostic criteria for diabetes yet. Prediabetes and DM were both significantly associated with the incidence of subclinical myocardial damage after 6 years, as assessed with a high-sensitivity assay for cardiac troponin T. Incident elevations in hs-cTnT were associated with CV events in the future, in particular heart failure and death. These data suggest that persons with prediabetes are not only at risk of developing DM, but also of progression of subclinical cardiac damage and consequently of CV events.
 
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