New Test Finds Diabetes' Silent Heart Damage

Using an experimental and highly sensitive test for cardiac troponin, a team of Johns Hopkins researchers found undetected signs of heart muscle damage in people with diabetes and pre-diabetes. That may suggest that hypoglycemia directly damages the heart.

The researchers focused on whether subjects had the protein troponin in their blood. A component of cardiac muscle, troponin is released when the heart is deprived of oxygen and cells die.Its presence in the blood has long been considered a reliable marker for deciding whether a patient has had a heart attack. The new test can find troponin even when doctors or patients have no suspicions that heart damage has happened.

In findings published in the journal Circulation lead author Elizabeth Selvin said the super-sensitive test showed that people who have diabetes or pre-diabetes do have elevated levels of troponin in their blood. A follow-up analysis also showed these patients went on to develop heart problems at higher rates than controls.

“Pre-diabetes and diabetes were independently associated with development of subclinical myocardial damage, and those persons with evidence of subclinical damage were at highest risk for clinical events,” Selvin and colleagues wrote.

The new test—available abroad but not yet approved in the US—detects very minute amounts of troponin.

The Johns Hopkins team looked at 9,331 patients with no signs of heart disease, using the test to measure troponin levels. All were participants in the ongoing Atherosclerosis Risk in Communities Study being conducted by the US Department of Health & Human Services National Heart, Lung, and Blood Institute.

They found that in this asymptomatic group about half had some troponin, but that diabetics and pre-diabetics had more of the protein. After following the patients for six years, the team found higher levels of troponin in patients with diabetes and pre-diabetes than in healthy patients.

At the study’s endpoint six years after that, they found the diabetics and pre-diabetics had higher rates of heart failure, death, and coronary heart disease. The findings suggest that hyperglycemia damages the myocardium. Exactly how that might occur is unknown, she wrote. It could be something happening at the microvascular level.