FROM THE NEW ENGLAND JOURNAL OF MEDICINE
An abnormal troponin T level of 14 ng/L or higher, as measured using a high-sensitivity assay, doubles the risk of cardiovascular events and death among patients who have stable ischemic heart disease and type 2 diabetes, according to a report published online Aug. 13 in the New England Journal of Medicine.
Moreover, an increase of more than 25% in troponin T level during the course of 1 year predicts a worse outcome than do stable or decreasing troponin T levels in this patient population, significantly increasing the rates of death from cardiovascular causes, MI, or stroke. These findings “raise the possibility that serial measurements of troponin concentration may improve its prognostic value, and that persistently elevated and increasing troponin concentrations may be the best predictor of adverse outcomes,” said Dr. Brendan M. Everett of the divisions of cardiovascular medicine and preventive medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston.
These findings have particular significance because the prevalence of elevated troponin T was fully 40% in this study, noted Dr. Everett and his associates.
To examine the possible relationship between elevated troponin T and adverse cardiovascular outcomes in patients who had both stable ischemic heart disease and diabetes, the investigators performed a post hoc analysis of data gathered in the Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes (BARI 2D) clinical trial, which compared outcomes between patients who underwent preventive percutaneous coronary intervention or CABG plus intensive medical therapy against those who received intensive medical therapy alone.
For their ancillary study, Dr. Everett and his colleagues focused on 2,285 of these participants who had high-sensitivity assays to measure very low cardiac troponin levels in plasma samples and who were followed for a mean of 5 years. At baseline, 897 (40%) of these patients had troponin T levels of 14 ng/L or higher, the current cutoff point for both men and women.
The 5-year incidence of the composite outcome of death from cardiovascular causes, MI, or stroke was 27.1% in patients with elevated troponin T at baseline, compared with 12.9% in those with normal troponin T. The between-groups differences in each of the individual components of this composite outcome were of similar magnitude, as were the between-group differences in the secondary outcomes of death from any cause and heart failure (N Engl J Med. 2015 Aug 13 [doi:10.1056/NEJMoa1415921]).
This association remained robust after the data were adjusted to account for numerous potentially confounding factors such as traditional CV risk factors, a history of MI, a history of heart failure, the severity of diabetes, glomerular filtration rate, ECG abnormalities, the number of coronary lesions, and the presence of an abnormal ejection fraction.
In a further analysis that divided patients into five groups according to their troponin T levels, adverse event rates were substantially higher than average only in the highest two categories: 14.0-23.0 ng/L and 23.0 ng/L and higher.
In another analysis, the investigators assessed outcomes in a subgroup of 1,984 participants who underwent troponin T testing both at baseline and 1 year later. Patients whose levels increased by more than 25% during that year – about 7% of this subgroup – showed significantly increased risk of all adverse outcomes, compared with patients whose troponin T levels either remained stable or decreased.
Prompt revascularization via percutaneous coronary intervention or coronary artery bypass surgery did not lower the risk of any adverse outcomes in patients who had elevated troponin T. It is therefore crucial that the troponin T assay, already in widespread use, not be used to justify revascularization procedures, the researchers wrote. At least on the basis of this study’s findings, such procedures appear to offer little benefit, they noted.
The National Heart, Lung, and Blood Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, and Roche Diagnostics supported the study. Dr. Everett reported ties with Roche, Novartis, and Genzyme; his associates reported ties to numerous industry sources.
