The new test measures troponin T, a marker for the biological process of cell death that leads to heart failure. Current cardiac troponin T blood tests do not detect troponin in seemingly healthy people and are often used in hospital emergency rooms to clarify whether the source of chest pain is a heart attack or something else.
The new test, not commercially available in the United States, detects troponin levels that are 10 times lower than previous tests. The researchers found the marker in two-thirds of people without symptoms age 65 or older whose blood samples were collected and stored for up to 18 years as part of a long-term cardiovascular research project.
"This is a very unique finding," said principal investigator Christopher deFilippi, associate professor of medicine at the University of Maryland School of Medicine and a cardiologist at the University of Maryland Medical Center.
"We found that the higher the level of troponin, the greater the individual was at risk for symptoms of heart failure or death from cardiovascular disease over the next 10-15 years. The meaning of these elevated levels was unknown until this point."
The study was based on a national research project, the Cardiovascular Health Study (CHS), which began in 1989 and followed more than 4,000 people age 65 and older who were not hospitalized, did not have symptoms of heart failure and were not experiencing an acute medical illness.
Blood samples of the study participants, who were ethnically and geographically diverse, were taken when they first entered the study and repeated after two-three years. Each participant was followed for about 12 years to see what, if any, heart-related diseases they developed, with the most recent follow-up visit in 2008.
The blood samples were stored at very low temperatures to stabilize the proteins in the samples for a period of 10-15 years. By preserving the blood samples in this way, researchers such as the University of Maryland team could look back in time with modern testing tools.
The researchers also found that troponin levels can change over time. Troponin levels rose in some study participants between the first and second blood samples, with a corresponding increase in their risk for heart disease. Conversely, the risks dropped in other participants whose blood samples showed a reduction in troponin levels.
"These fluctuations suggest that even in people without clinical symptoms of heart disease, we may be able to intervene with lifestyle modifications to lower their risks," says deFilippi.
"This study may have important clinical implications, since it suggests that physicians need to consider that test results are more dynamic over time and that risk factors are also likely to change over time," says E. Albert Reece, vice president for medical affairs at the University of Maryland and dean of the University of Maryland School of Medicine.
Results of the study have been presented at the Scientific Sessions of the American Heart Association and simultaneously published online in JAMA, Journal of the American Medical Association. (ANI)