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Marker of Damage to Heart Muscle Rises with Rising A1cs in The Normal RangeA study published in February 2012 found that when a new high-sensitivity test that detects tiny amounts of a protein associated with heart muscle damage, troponin T, was used, study subjects were 24% more likely to have high cardiac troponin T if their A1c was between 5.7%-6.4%, compared to those whose A1c was below 5.7%. When their A1cs were over 6.4% that likelihood doubled. This suggests high blood sugars in the upper part of the range most doctors consider normal directly damage heart muscle.
Chronic Hyperglycemia and Subclinical Myocardial Injury.
Jonathan Rubin et al. J.Am.Col.Cardiology,Volume 59, Issue 5, 31 January 2012, Pages 484–489 http://dx.doi.org/10.1016/j.jacc.2011.10.875,