Measurement of myocardial infarct size from plasma fatty acid-binding protein or myoglobin, using individually estimated clearance rates.
OBJECTIVE
In patients with acute myocardial infarction (AMI), estimation of infarct size from the early markers, fatty acid-binding protein (FABP) and myoglobin (MYO), usually assumes average (fixed) rate constants (FCR) for protein clearance from plasma. However, individual variation in FCR is large. Renal dysfunction causes slower clearance of FABP and MYO from plasma and, hence, overestimation of infarct size in 20-25% of patients. We investigated whether or not more accurate values of infarct size could be obtained with individually estimated clearance rates.


METHODS
Concentrations of FABP and MYO and, for comparison, activities of the established cardiac markers, creatine kinase (CK) and alpha-hydroxybutyrate dehydrogenase (HBDH), were assayed in serial plasma samples from 138 patients with AMI. Individual FCR values of FABP and MYO were estimated from plasma creatinine concentrations, sex and age.


RESULTS
Individual FCR values varied from 0.4 to 2.4 h-1. Use of these individual FCR values significantly improved the correlation between infarct size, as estimated from FABP or MYO on the one hand, and from CK and HBDH on the other. Approximately equal estimates of infarct size were obtained for all four marker proteins.


CONCLUSIONS
Using individually estimated clearance rates, renal insufficiency no longer hampers calculation of infarct size from FABP and MYO, and reliable estimates of total myocardial damage can be obtained within 24 h after first symptoms.
de Groot
M J
MJ
Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands.
Wodzig
K W
KW
Simoons
M L
ML
Glatz
J F
JF
Hermens
W T
WT
D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D002352:Carrier Proteins / Q000097:blood* / Q000378:metabolism; D003402:Creatine Kinase / Q000097:blood; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005260:Female; D006801:Humans; D006884:Hydroxybutyrate Dehydrogenase / Q000097:blood; D007668:Kidney / Q000503:physiopathology; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D018996:Myelin P2 Protein / Q000097:blood* / Q000378:metabolism; D009203:Myocardial Infarction / Q000097:blood / Q000473:pathology* / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D009211:Myoglobin / Q000097:blood* / Q000378:metabolism; D009363:Neoplasm Proteins; D018709:Statistics, Nonparametric; D013997:Time Factors; D025521:Tumor Suppressor Proteins
D015415:Biomarkers; D002352:Carrier Proteins; C107608:FABP7 protein, human; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D018996:Myelin P2 Protein; D009211:Myoglobin; D009363:Neoplasm Proteins; D025521:Tumor Suppressor Proteins; D006884:Hydroxybutyrate Dehydrogenase; D003402:Creatine Kinase