A person who has diabetes and is feeling quite well, not outwardly showing any evidence of heart disease, may secretly be a ticking time bomb.
You may suspect the danger lurks in cholesterol or atherosclerosis-but no, a new study has found that a substantial group of people with diabetes face heightened risk of heart failure and cardiac death from something other than the usual suspects. The risk could instead stem from miniscule amounts of protein secreted into the bloodstream when heart cells die.
"It puts what we know about heart damage in diabetes on its head," says study leader Elizabeth Selvin, PhD, MPH, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, Baltimore. "It looks like diabetes may be slowly killing heart muscle in ways we had not thought of before."
The aforementioned protein-called troponin-was discovered by the investigators using an extremely sensitive blood test.
When a person experiencing chest pain or other symptoms of heart attack arrives in the emergency room, he or she is given a test that measures levels of troponin proteins in the blood. (During a heart attack, troponin proteins are released into the blood.) The levels of these proteins is generally very low, and even a very small spike could signal some heart damage.
The stealth damage may put a person's health at risk-and the researchers say these individuals could have a six times greater chance of developing heart failure, regardless of their cholesterol levels. Having a test that measures these small increases in troponin levels may one day help screen for early chronic heart damage, Selvin says.
The troponin test used for this study is 10 times more acute than tests available on the market and detects minute levels of troponins-and in the process, finds heretofore hidden subclinical recurring damage to the heart. The test is for research-use only, and is not yet offered for sale in the United States.
More than 9,000 people participated in this study over a period of several years. Almost one-half of those with diabetes in the study group were found to have invisible damage to their heart muscle that may have been caused by elevated blood sugar.
For people with diabetes, heart disease is indeed the primary cause of death, and atherosclerosis is often the underlying cause. (Atherosclerosis, an accumulation of fats, cholesterol, and other substances in and on the artery walls can hinder or entirely block blood flow. It can impact arteries throughout the body, not just in the heart.)
When physicians first diagnose a patient with diabetes they often prescribe statins (drugs) due to the correlation between diabetes and heart disease, as statins help lower cholesterol levels. The risk of heart disease faced by some with diabetes may not be linked to cholesterol levels, the findings suggest.
"Statin treatment may not be sufficient to prevent damage to the heart in people with diabetes," she says. "Even though there may be no symptoms yet, our research suggests there is microvascular damage being done to the heart which is leading to heart failure and even death."
Selvin says more research is needed to identify precisely how diabetes may be causing the heart damage.
To learn more, read the article in the journal Circulation (also available online), titled Diabetes, pre-diabetes and Incidence of Subclinical Myocardial Damage," by Elizabeth Selvin, Mariana Lazo, Yuan Chen, et al.