For patients with type 2 diabetes and stable ischemic heart disease, measuring their cardiac troponin T concentration may help predict their risk of death from cardiovascular causes, nonfatal MI or nonfatal stroke, according to an analysis of a randomized study.
After five years, 27.1 percent of patients with abnormal troponin T concentrations at baseline had achieved the composite endpoint of death from cardiovascular causes, nonfatal MI or nonfatal stroke compared with 12.9 percent of patients with normal troponin T concentrations.
Among patients with abnormal troponin T concentrations, the researchers also found that the rates of the composite endpoint were similar whether they were randomly assigned to undergo revascularization or medical therapy alone.
Of the patients, 39.3 percent had abnormal troponin T concentrations at baseline, which was defined as at least 14 ng per liter.
Results were published online in the New England Journal of Medicine on Aug. 13. The National Institutes of Health and Roche Diagnostics funded the study.
“It was surprising how common an abnormal troponin was in this population,” lead researcher Brendan M. Everett, MD, MPH, of Harvard Medical School and Brigham and Women’s Hospital in Boston, told Cardiovascular Business. “That means patients with diabetes and stable heart disease, nearly 40 percent of them, are walking around with a circulating troponin that’s in the abnormal range. That reflects ongoing heart injury in those patients.
"The other surprising thing was that opening the coronary arteries of these patients, whether we did it with balloons and stenting or whether it was done with bypass surgery, did not seem to offer benefit even to those patients with the evidence of ongoing heart injury as indicated by an abnormal troponin.”
Everett said doctors commonly use cardiac troponin as a biomarker to diagnose MI in patients who present to the emergency department with chest pain. The high-sensitivity assay used in this study is not FDA-approved, according to Everett. However, he added the assay detects lower levels of cardiac troponin in the bloodstream compared with commercially available assays in the U.S.
The researchers used the assay to measure cardiac troponin T concentration from 2,277 patients with type 2 diabetes and stable ischemic heart disease who had ongoing heart injury and enrolled in the BARI 2D (Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes) trial. During the study, which began on Jan. 1, 2001, patients with type 2 diabetes and stable heart disease with minimal symptoms of angina were randomized to receive prompt coronary revascularization plus intensive medical therapy or intensive medical therapy alone. The study found that the revascularization strategy did not offer patients any benefit.
The researchers also noted that significantly more patients with abnormal troponin T concentrations at baseline died from any cause or had an MI, stroke or heart failure.
If the FDA approves the assay used in this study, Everett said it would likely be indicated to diagnose MI in patients presenting to the emergency room with chest pain. He predicted the assay would not be used for monitoring stable patients as it was used in this study. As of now, there is no therapy that will alter abnormal troponin concentration levels in stable patients.
Everett said the researchers were surprised that so many patients had abnormal troponin levels and that opening the arteries did not improve the patients’ risk of a poor outcome or their troponin concentrations.
“What that tells me is that there is a different underlying cause for this abnormal troponin than what we traditionally think of as the cause of an abnormal troponin, which is a blocked artery that requires a balloon and a stent to open or bypass surgery to open,” he said. “There’s some other process going on that causes the low level heart injury. It’s not really ameliorated by opening the arteries. That gives us the opportunity to identify new strategies for treating these patients and to hopefully make their outcomes better, to reduce their risks of heart attack and stroke and heart failure and cardiovascular death.”