NEW YORK — An experimental, highly sensitive troponin test cannot predict when type 2 diabetics with stable ischemic heart disease will benefit from prompt coronary revascularization, but it can show which patients are more likely to die from myocardial infarction, stroke, or other cardiovascular cases, according to a new study.
Because the troponin test measures damage to heart muscle, the outcome "suggests there's ongoing injury to patients with stable heart disease and diabetes. It has a strong association with death, heart attack, stroke, heart failure," the chief author, Dr. Brendan Everett, director of inpatient general cardiology at Brigham and Women's Hospital in Boston, told Reuters Health in a telephone interview.
But when it comes to heading off a higher risk, "we need to do more research to understand where it's coming from and what therapies might be appropriate. So it does not appear in this population that opening the coronary arteries offers any long-term benefit with respect to death or heart attack," he said.
"It tells you this is not the type of disease status that can be managed by bypass or stenting," said Dr. David Zhao, chairman of cardiology at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina. He was not involved in the research.
"From the patient's standpoint, it is disappointing," Dr. Zhao said. "But from a science standpoint, it all comes together nicely. These patients tend to have more small-vessel microvascular disease and the constant elevation of troponin indicates that there is more severe microvascular disease and more endomyocardial injury. I think it gives us the opportunity to look at more intensified medical management in this group of patients."
The study was an offshoot of the BARI 2D trial, conducted at 49 sites in six countries. It found that aggressive revascularization didn't reduce the risk of death or cardiovascular outcomes compared to intensive medical therapy alone in type 2 diabetics with stable heart disease.
In the new research, the team went back and used a highly sensitive troponin test sold in Europe but not available in the United States to see "if it could be used in stable patients to identify those who would benefit from having their coronary arteries opened with either angioplasty and stenting or bypass surgery," Dr. Everett said.
"There aren't many studies addressing that question and luckily BARI 2D had samples that were stored and available to us after the completion of the trial," he said. "What we did find was that there's clearly a group of patients that are at very high risk for death, heart attack, heart failure, and stroke."
The researchers found 27.1% of patients with a troponin T level of 14.0 ng/L or higher died from cardiovascular cause, or had a heart attack or stroke, compared to 12.9% of patients whose levels were lower, they reported online August 12 in the New England Journal of Medicine.
Adjusting for various factors, the risk of reaching one of those primary endpoints after five years was 85% greater with the higher troponin levels (P<0.001).
The risks for reaching individual components of the composite endpoint were also higher. Unadjusted five-year rates for patients with higher versus lower troponin levels were, respectively, 10.9% versus 3.5% for cardiovascular death, 18.7% versus 9.2% for myocardial infarction, 4.4% versus 2.3% for stroke, and 25.7% versus 11.1% for heart failure.
The Everett team also found that among the 897 volunteers whose levels had been at 14 or above, receiving a prompt intervention did not reduce their likelihood of reaching a primary endpoint compared to the 2,277 with normal concentrations.
The five-year rates of heart attack, stroke, or death from any cardiovascular cause were 26.5% in the revascularization group and 27.6% with medical therapy alone.
"We need to figure out how to better treat them, because fixing their coronary arteries doesn't seem to be giving them the benefit we thought it would, or hoped it would," said Dr. Everett. "For the time being, this is not a test that should be routinely used on stable patients."
The researchers also looked at how troponin levels changed over time.
"Despite aggressive medical therapy for type 2 diabetes and stable ischemic heart disease, the median troponin T concentration increased over one year of follow-up, and no significant reductions in troponin T concentrations were observed in patients who underwent coronary revascularization," the researchers said.
"If this type of patient has elevated troponin, I would be more aggressive in medical management, including statins, smoking cessation, and lifestyle changes," said Dr. Zhao of Wake Forest. "I think the next step would be to ideally run a clinical trial and see if, in patients with elevated troponin levels, intensified medical management reduces the number of events as compared to standard therapy.