Records on follow-up cTnT levels, measured 2-3 years after baseline in 86% of the study participants, showed that among those with a detectable cTnT level at baseline, nearly two-thirds stayed at about the same level, 22% increased by more than 50%, and 14% decreased by more than 50%.
The high increasers had their subsequent heart failure and cardiovascular death rates rise by about 50% compared with people with more moderate changes.
In contrast, among those whose levels fell by more than 50% during follow-up subsequent event rates dropped by about 25% compared with those with less change in their cTnT level.
Concurrent with Dr. deFilippi's talk at the meeting the findings also appeared in an article published online in JAMA (2010; 304:doi:10.1001/jama.2010.1708).
The results also identified some people with very high levels at baseline that then fell to an undetectable level at their second cTnT measurement. Few people showed this kind of change, but it occurred often enough for Dr. deFilippi to speculate that certain actions can effectively lower serum cardiac troponin T levels.
The source of the cTnT isn't clear. Dr. deFilippi believes it's caused by a chronic process, although the specifics remain unknown. “It's unlikely an ischemic cause,” he said. “The issue is, once you see [a high level] can you intervene? Right now, that's an open question.”
Over 12 years, the rates of heart failure and cardiac death tracked along with baseline cTnT levels.
Source DR. DEFILIPPI
Other Studies Using High-Sensitivity Test Support cTnT's Risk-Marker Role
CHICAGO – In addition to the report by Dr. deFilippi, three other research groups recently reported finding significant links between elevated serum levels of cardiac troponin T and an increased risk for cardiovascular events:
▸ Researchers measured cardiac troponin T (cTnT) using a high-sensitivity assay in 10,820 Americans aged 53-75 without prevalent cardiovascular disease enrolled in the Atherosclerosis Risk in Communities (ARIC) study. In these people, with an average age of 63 years, 61% had a detectable level of serum cTnT at baseline using the high-sensitivity test. During an average follow-up of 10 years, Researchers found a significant link between detectable levels at baseline and death and hospitalization for heart failure during follow-up, Dr. Justin T. Saunders from Baylor College of Medicine in Houston reported at the scientific sessions.
▸ In a second, independent study, researchers measured serum cTnT with the high-sensitivity assay in women enrolled in the Women's Health Study. The current analysis focused on 512 women with diabetes at the time of their serum sampling and 564 women without diabetes. Among the women with diabetes, detectable levels of cTnT excisted in 56% of those who had cardiovascular disease events during follow-up and in 42% of the women who did not later have an event, a statistically significant difference. The event that seemed most responsible for this difference was cardiovascular disease death. Among the women without diabetes, detectable levels of cTnT appeared to have no significant relationship to subsequent cardiovascular disease events. Detectable cTnT appeared in 34% of the women with a subsequent event and in 30% of those without a later event, Dr. Brendan M. Everett from Brigham and Women's Hospital in Boston reported at the scientific sessions.
▸ In the third study, researchers ran high-sensitivity cTnT measures on 3,546 people aged 30-65 enrolled in the Dallas Heart Study. They found detectable levels in 25% of the participants. The prevalence of detectable levels depended on age and gender. People younger than 40 had a prevalence rate of 14% compared with a prevalence of 58% in people aged 65 or older. Men had a prevalence rate of 37%, compared with a rate of 13% in women. During a median follow-up of 6.4 years, in an analysis that adjusted for a series of baseline variables and risk factors, people in the highest quintile for serum cTnT level had a statistically significant, greater than fourfold increased risk for both all-cause death and cardiovascular death, said Dr. James A. de Lemos, from the University of Texas Southwestern Medical Center, and his associates in a report published in the Dec. 8, 2010, issue of JAMA (2010;304:2503-12).
Dr. Saunders had no disclosures.
Dr. Everett said he had received research grants from Roche Diagnostics.
Dr. de Lemos said that he has received research grants from Roche Diagnostics and Biosite, and consulting fees, lecture honoraria, or both from Tethys Biomedical, Johnson & Johnson, Roche Diagnostics, Biosite/Invemess, Siemens, AstraZeneca, Pfizer, Bristol Myers Squibb/Sanofi Aventis, and Merck.
– Mitchel L. Zoler