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High-Sensitivity Troponins and Outcomes After MI
Study Questions:
How has high-sensitivity cardiac troponin T (hs-cTnT) affected the incidence, prognosis, and use of coronary angiography in patients with myocardial infarction (MI) compared to conventional cardiac troponin (cTn)?
Methods:
The authors conducted a cohort study of patients with a first MI from the Swedish National Patient Registry from 2009-2013. MI was defined as either cTn or hs-cTnT >99th percentile value. The primary outcome was all-cause mortality, and secondary outcomes were reinfarction, coronary angiography, and coronary revascularization. Cox proportional hazard models were used to calculate the association between patients tested with cTn and patients tested with hs-cTnT for the primary and secondary outcomes. For each outcome, an unadjusted and adjusted model were conducted, the latter adjusting for covariates including sex, chronic kidney disease, hospital, heart failure, prior stroke, chronic obstructive pulmonary disease, diabetes, previous cardiac revascularization, and treatment with aspirin, P2Y12 inhibitors, beta-blockers, angiotensin-converting enzyme inhibitors/angiotensin-receptor blocker, and statins. Patients were followed until death or the end of follow-up (March 2016), whichever came first. Mean follow-up was 3.9 ± 2.8 years.
Results:
The study cohort consisted of 87,879 patients with a first MI, of whom 57,133 (54%) were diagnosed using cTn and 40,756 (46%) were diagnosed using hs-cTnT. Compared to the 90 days prior to the introduction of hs-cTnT, the 90 days following the introduction of hs-cTnT showed a 5% increase (95% confidence interval [CI], 0%-10%) in the number of MIs. During follow-up, there were 33,492 (38%) deaths in the cohort: 20,115 in the cTn group and 13,377 in the hs-cTnT group. There was no difference in the risk of all-cause mortality in the hs-cTnT group (hazard ratio [HR], 1.00; 95% CI, 0.97-1.02), and there was no difference in the risk of all-cause mortality in sex-specific analysis. There was an 11% relative risk reduction for reinfarction in the hs-cTnT group compared to the cTn group (adjusted HR, 0.89; 95% CI, 0.86-0.91), with a similar risk reduction for both men and women. Patients with MI diagnosed by hs-cTnT were 16% more likely to undergo coronary angiography (adjusted HR, 1.16; 95% CI, 1.14-1.18) and were 13% more likely to undergo revascularization within 30 days of MI (adjusted HR, 1.13; 95% CI, 1.11-1.15).
Conclusions:
In this observational cohort study of patients with a first MI in Sweden from 2009-2013, having MI diagnosed with hs-cTnT was not associated with a change in all-cause mortality. Use of hs-cTnT for diagnosis of MI was associated with small reductions in the risk of reinfarction and a small increase in coronary angiography and coronary revascularization.
Perspective:
This study analyzed the associations of hs-cTnT with all-cause mortality, coronary angiography, and revascularization during the time period in which 73% of acute care hospitals in Sweden transitioned from cTn to hs-cTnT. The introduction of hs-cTnT was not associated with an all-cause mortality benefit, but was associated with a reduced risk of reinfarction and increase in coronary angiography and revascularization. The reduced risk of reinfarction may be related to the increase in coronary angiography/revascularization, although in the context of an observational study, this is hypothesis generating. If the increase in angiography or revascularization was associated with improved prognosis, the overall benefit would have to be weighed against the additional cost and possible risks associated with these procedures. Broadly, as hs-cTnT becomes increasingly more available, clinicians will have to gain experience in the interpretation of hs-cTnT results, and further investigations are needed to refine clinical decision making with the goal of improving patient care.
Keywords: Acute Coronary Syndrome, Angiography, Biomarkers, Metabolic Syndrome, Coronary Angiography, Myocardial Infarction, Myocardial Revascularization, Outcome Assessment, Health Care, Patient Care, Risk, Risk Reduction Behavior, Secondary Prevention, Troponin, Troponin T
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