Outcomes associated with small changes in normal-range cardiac markers.
BACKGROUND
Troponin concentrations rising above an institutional cutpoint are used to define acute myocardial necrosis, yet it is uncertain what outcomes are associated with fluctuations in troponin that do not exceed this level. We evaluate the association between troponin fluctuations below an institutional upper limit of normal and acute coronary syndrome (ACS).


METHODS
This was a post hoc analysis of the Internet tracking registry of ACS (i*trACS), which describes patients presenting to emergency departments (EDs) with suspected ACS across the spectrum of risk. Patients were included in this registry if they were at least 18 years old and had suspected ACS at the time of their ED visit. Inclusions in this analysis required that patients had at least 1 cardiac marker (creatine kinase-MB [CK-MB], troponin T, or troponin I) drawn twice within 6 hours of presentation, with both measures being below the institution's upper limit of normal. A marker change was defined as either an increase or decrease that exceeded 15% of the institutional upper limit of normal. Acute coronary syndrome was defined as a positive stress test, documented myocardial infarction, coronary revascularization, or death within 30 days of their ED admission.


RESULTS
Of 17,713 patient visits, 2162 met inclusion and exclusion criteria. There were 1872 patient visits with 2 troponin results and 1312 with 2 CK-MB results. Patient visits with increasing troponin had increased odds of ACS compared with those with stable troponin levels (odds ratio, 3.6; 95% confidence interval, 1.4-9.2). Changing CK-MB and decreasing troponin were not associated with increased odds of ACS.


CONCLUSIONS
Small increases in troponin concentration below the upper limit of normal are associated with increased odds of ACS.
McMullin
Nolan
N
The Cleveland Clinic, Cleveland, OH, USA.
Lindsell
Christopher J
CJ
Lei
Lei
L
Mafi
John
J
Jois-Bilowich
Preeti
P
Anantharaman
Venkataraman
V
Pollack
Charles V
CV
Hollander
Judd E
JE
Gibler
W Brian
WB
Hoekestra
James W
JW
Diercks
Deborah
D
Peacock
W Frank
WF
D054058:Acute Coronary Syndrome / Q000097:blood* / Q000175:diagnosis; D015415:Biomarkers / Q000097:blood; D052279:Creatine Kinase, MB Form / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood* / Q000175:diagnosis; D017063:Outcome Assessment, Health Care; D011379:Prognosis; D012042:Registries; D019210:Troponin I / Q000097:blood*; D020107:Troponin T / Q000097:blood*
D015415:Biomarkers; D019210:Troponin I; D020107:Troponin T; D052279:Creatine Kinase, MB Form