The prognostic value of serum myoglobin in patients with non-ST-segment elevation acute coronary syndromes. Results from the TIMI 11B and TACTICS-TIMI 18 studies.
OBJECTIVE
The goal of this study was to define the prognostic value of serum myoglobin in patients with non-ST-elevation acute coronary syndromes (ACS).


BACKGROUND
While myoglobin is useful for the early diagnosis of myocardial infarction (MI), its role in the early risk-stratification of patients with ACS has not been established.


METHODS
Myoglobin, creatine kinase-MB subfraction (CK-MB) and troponin I (cTnI) were measured at randomization in 616 patients from the Thrombolysis In Myocardial Ischemia/Infarction (TIMI) 11B study and 1,841 patients from the Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Therapy-Thrombolysis In Myocardial Ischemia/Infarction (TACTICS-TIMI) 18 study. The risks for death and nonfatal MI through six months of follow-up were compared between patients with and without myoglobin elevation (>110 microg/l) in each study and in a dataset combining all eligible patients from both studies (n = 2,457).


RESULTS
In a multivariate model adjusting for baseline characteristics, ST changes and CK-MB and cTnI levels, an elevated baseline myoglobin was associated with increased six-month mortality in TIMI 11B (adjusted odds ratio [OR] 2.9 [95% confidence interval [CI] 1.2 to 7.1]), TACTICS-TIMI 18 (adjusted OR 3.0 [95% CI 1.5 to 5.9]) and the combined dataset (adjusted OR 3.0 [95% CI 1.8 to 5.0]). In contrast, there was no significant association between myoglobin elevation and nonfatal MI (combined dataset adjusted OR 1.55, 95% CI 0.9 to 2.6). In TACTICS-TIMI 18, patients with versus those without myoglobin elevation were more likely to have an occluded culprit artery (28% vs. 10%; p < 0.0001) and visible thrombus (49% vs. 34%; p = 0.006) and less likely to have TIMI 3 flow (53% vs. 68%; p = 0.009).


CONCLUSIONS
A serum concentration of myoglobin above the MI detection threshold (>110 microg/l) is associated with an increased risk of six-month mortality, independent of baseline clinical characteristics, electrocardiographic changes and elevation in CK-MB and cTnI. These findings suggest that myoglobin may be a useful addition to cardiac biomarker panels for early risk-stratification in ACS.
de Lemos
James A
JA
Thrombolysis In Myocardial Infarction (TIMI) Study Group, Reynolds Cardiovascular Clinical Research Center, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75390-9047, USA. james.delemos@utsouthwestern.edu
Morrow
David A
DA
Gibson
C Michael
CM
Murphy
Sabina A
SA
Sabatine
Marc S
MS
Rifai
Nader
N
McCabe
Carolyn H
CH
Antman
Elliott M
EM
Cannon
Christopher P
CP
Braunwald
Eugene
E
D000208:Acute Disease; D000368:Aged; D000704:Analysis of Variance; D000787:Angina Pectoris / Q000097:blood; D015415:Biomarkers / Q000097:blood; D016001:Confidence Intervals; D003327:Coronary Disease / Q000097:blood* / Q000503:physiopathology / Q000628:therapy; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood; D017202:Myocardial Ischemia / Q000097:blood; D009211:Myoglobin / Q000097:blood*; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011379:Prognosis; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012306:Risk; D015912:Thrombolytic Therapy
D015415:Biomarkers; D009211:Myoglobin