MI Rates Rise After Introduction of High-sensitivity Troponins

By Will Boggs MD, Reuters Health
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NEW YORK (Reuters Health) - The rates of myocardial infarction (MI) diagnosis and treatment increased after the introduction of high-sensitivity cardiac troponins (hs-cTnT), with no impact on overall survival, researchers report.

"I know that in the U.S. there has been a lot of concern about the introduction of the high-sensitivity assays," senior author Dr. Martin J. Holzmann from Karolinska Institutet, in Stockholm, told Reuters Health by email. "I believe our study is one more study that suggests that these assay not only help us in the assessment of patients in the emergency department (ED), but also that patients with MI will benefit from them."

Cardiac invasive specialist. (Source: Nellis Air Force Base)

 Despite concerns that implementation of hs-cTnT assays could diminish the clinical specificity for MI diagnosis and lead to increased use of resources, most studies have found their introduction to be associated with small or no increases in coronary angiography and revascularization but with sharp declines in admission rates for chest pain.

 Dr. Holzmann and colleagues used data from nationwide Swedish registries to investigate the impact of the introduction of hs-cTnT assays on the risk of mortality, reinfarctions and resource use in more than 87,000 unselected MI patients, including 47,133 diagnosed with cardiac troponins (cTn) and 40,746 diagnosed using hs-cTnT.

 The overall incidence of MI increased by 5% in the 90 days following the introduction of hs-cTnT assays, compared with the 90 days that preceded their introduction. But the difference was not consistent across hospitals: Some reported increased numbers of MIs and others reported decreased numbers.

During a mean follow-up of 3.9 years, all-cause mortality (the primary endpoint) did not differ between patients diagnosed with cTn and patients diagnosed with hs-cTnT, the team reports in the Journal of the American College of Cardiology, online June 12.

 Patients diagnosed with MI using hs-cTnT were 11% less likely to have reinfarctions and were 16% more likely to undergo coronary angiography and 13% more likely to undergo revascularization within 30 days of MI, compared with patients diagnosed with MI using cTn. All of the differences were significant.

"We did not expect an improved survival, but it was somewhat surprising that the risk of reinfarction was reduced in patients tested with the hs-cTnT assay," Dr. Holzmann said.

At the hospital level, coronary angiographies increased 3% and revascularizations increased 4% in the 90 days after introduction of the hs-cTnT assay; neither difference was statistically significant.

"As hs-cTn assays become widely available and clinicians gain experience interpreting the results, more work is needed to enhance clinical reasoning and implementation to improve patient outcomes," the researchers note.

"I think that the few hospitals in countries like Sweden, where we have used the high-sensitivity assays for some years already, who are not using them should start doing that," Dr. Holzmann said. "And for the U.S. hospitals who are hesitant about whether to start using the high-sensitivity assays or not, this paper is yet another paper that suggests that most likely hospitals and patients will benefit from the introduction of these assays."

Dr. L. Kristin Newby from Duke University Medical Center, in Durham, North Carolina, who co-authored an accompanying editorial, told Reuters Health by email, "I am intrigued by the finding that among the subgroup of patients diagnosed with MI, those diagnosed with hs-cTnT had more angiography and revascularization and a lower subsequent rate of MI than those diagnosed with conventional Tn, though it is premature to draw any conclusions without more information to understand what is driving these associations."

"I think this study should help to allay some of the concerns that U.S. cardiologists have about the impact of implementation of hs-cTnT testing on volume of MIs or that it will drive increased use of angiography and intervention," she said.

"There is substantial prior experience (8 years) with the clinical implementation and use of hs-cTnT testing outside of the U.S.," Dr. Newby explained. "Although there will be some challenges, the upsides of hs-cTnT testing are tremendous. We do not have to 'reinvent the wheel'; we can learn from reports like this and the extensive practice experience outside of the U.S. to educate our healthcare teams, administrators, etc., enabling us to take informed action and enlightened approaches for the rollout of hs-cTnT testing at our U.S. institutions and continue to tailor our approaches through surveillance and active learning from our experiences."

Dr. David E. Winchester from the University of Florida, in Gainesville, who has also examined associations between cardiac troponin, mortality, and use of cardiovascular services, told Reuters Health by email, "One prominent speculation about adoption of hs-troponin is that the diagnosis of unstable angina would be substantially reduced or eliminated. The reasoning is that the increased sensitivity of the assay would make it possible to detect even the smallest amount of myocardial necrosis. This study showed that the overall incidence of unstable angina was not substantially reduced during the study period."

"Physicians would be wise to plan ahead for hs-troponin adoption with an interdisciplinary team of groups affected by the change," said Dr. Winchester, who was not involved in the Swedish research. "Implementation science is lacking on the best strategies for adopting hs-troponin. Facilities yet to adopt hs-troponin would likely benefit from study of best practices for the assay.​"

One of Dr. Holzmann's coauthors is on the speakers' bureau of Roche, which produced the hs-cTnT assay used in the study.

SOURCE: https://bit.ly/2Jy5lKE and https://bit.ly/2Jzq2pj

J Am Coll Cardiol 2018.

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