Elevated Troponin Levels Increase CV Risk in Diabetics

Levels of cardiac troponin I (cTnI) were slightly raised–that is, they were measurable but not high enough to qualify as MI–in more than a fifth of a series of stable patients with diabetes referred for diagnostic coronary angiography.

Moreover, those with such subclinical myocardial necrosis, compared with the remaining 78% of patients, showed about a 50% higher risk of major adverse cardiac events (MACE) over three years independently of standard CV risk factors, glycosylated hemoglobin (HbA1C) and other diabetes measures, and history of MI or cardiac procedures.

Dr WH Wilson Tang (Cleveland Clinic, OH) and associates wrote, "The findings would appear to imply that any detectable cTnI level should warrant consideration for more globally aggressive risk-reduction efforts, including closer evaluation and long-term monitoring, and such intervention efforts may focus beyond glycemic-control measures." Although it can be useful to think of diabetes per se as a coronary-disease equivalent, the current findings suggest there may be an "intermediate phenotype" of asymptomatic diabetic patient that also has an undefined chronic condition characterized by cTnI leakage and increased CV risk."

Dr. Tang added that, "Right now we don’t routinely measure troponins, and rightfully so. I think this is a first step to examining troponin not simply as a diagnostic measure of acute MI or acute coronary syndromes, but also for identifying individuals with diabetes who have higher risk, to either more aggressively treat them or find strategies to lower their risk."

He and his colleagues acknowledge their data don’t necessarily show that the cTnI elevations represent an ongoing process of myocardial damage that could be targeted for therapy. But, Tang said, they are consistent with other research showing that many apparently healthy people and patients with chronic diseases, including chronic kidney disease, have silently elevated troponins that can predict outcomes.

He and his colleagues retrospectively looked at 1275 stable patients with diabetes but no evidence of acute coronary syndromes undergoing diagnostic angiography from 2001 to 2006 as part of a prospective cohort study. They included only patients with cTnI below the MI threshold of 0.03 ng/mL, no history of revascularization within the prior month, and at least three years of follow-up data.

Of those patients, 22% showed cTnI levels of 0.009 to 0.029 ng/mL, the study’s definition for subclinical myocardial necrosis (p<0.001 vs. all other patients); another 34% had lower but detectable levels.

Subclinical myocardial necrosis was associated with an independent, significantly increased MACE risk over three years; it was only weakly associated with measures of glycemia, falling short of or barely reaching significance.

"We have always associated [troponin elevations] with acute coronary syndromes, but studies like this one, with a broad population, show there are lots of people who have an ongoing process [of myocardial necrosis] that’s yet to be defined and not part of the continuum of acute coronary syndromes," Tang said. "Certainly these people are in a much higher risk category that we need to pay some attention to."

Tang WH, Wu Y, Britt EB Jr, et al. "Detectable subclinical myocardial necrosis is associated with cardiovascular risk in stable patients with diabetes mellitus" Diabetes Care 2013; DOI: 10.2337/dc11-1969. Diabetes Care, Feb. 7, 2013