CHICAGO – "Measurement of cardiac troponin T using a highly sensitive assay may be useful in risk stratification in older adults," Dr. Stephen L. Seliger declared in presenting study findings at the annual scientific sessions of the American Heart Association.
The investigational assay was an independent predictor of cardiovascular mortality in a longitudinal observational cohort study of 4,221 ambulatory, community-dwelling adults aged 65 years or older without prior heart failure. The cohort participated in the nationwide Cardiovascular Health Study, a National Institutes of Health–funded study of cardiovascular risk in the elderly. During a median 11.8 years of follow-up, 1,100 of them died of cardiovascular causes.
At baseline, serum cardiac troponin T (cTnT) was 3.0 pg/mL or more in 66% of the subjects. Cardiovascular deaths rose with increasing baseline cTnT, from a low of 1.1 cases per 100 person-years in those with undetectable cTnT to a high of 4.8 per 100 person-years in subjects in the top quartile of detectable cTnT, with a level greater than 12.94 pg/mL.
The incidence of cardiovascular mortality was 1.6 per 100 person-years in individuals with a baseline cTnT of 3.00-5.44 pg/mL, 2.3 cases per 100 person-years in those with a value of 5.45-8.16 pg/mL, and 3.0 per 100 person-years in subjects with a cTnT of 8.17-12.94 pg/mL, added Dr. Seliger of the University of Maryland, Baltimore.
A higher baseline cTnT was strongly predictive of cardiovascular mortality independent of the traditional cardiovascular risk factors as well as the widely used biomarkers N-terminal pro-type B natriuretic peptide and C-reactive protein. In a multivariate analysis adjusted for these variables, a cTnT greater than 12.94 pg/mL was associated with a 2.1-fold greater risk of cardiovascular death than was an undetectable level of cTnT. Subjects in quartiles 1-3 for detectable cTnT had adjusted risks that were, respectively, 1.3-, 1.45-, and 1.58-fold greater than in individuals with an undetectable cTnT.
Not only was a higher baseline cTnT associated with increased risk of cardiovascular mortality, but so were changes in cTnT over time, regardless of the absolute baseline level. Among the two-thirds of elderly individuals who had a detectable baseline cTnT, 22% had a 50% or greater increase in cTnT over the next several years; their long-term risk of cardiovascular death was 70% greater than that of subjects without an increase of that magnitude.
In contrast, the 14% of subjects who showed a 50% or greater reduction in cTnT compared with baseline had a 30% lower cardiovascular mortality rate than did those with less than a 50% change in cTnT level over the first several years of follow-up.
The underlying cause of these small elevations in cTnT – changes undetectable using standard assays – remains unclear. It’s possible that the enzyme is being released as a consequence of increased left ventricular mass or perhaps because of chronic hypertension. Preliminary work by Dr. Seliger and his coinvestigators suggests the cTnT release may be due to a metabolic alteration involving changes in fatty acid oxidation patterns.
Dr. Seliger declared he serves as a consultant to Roche Diagnostics, which is developing the highly sensitive cTnT assay.