FATTY-ACID-BINDING PROTEIN AS A PLASMA MARKER FOR THE ESTIMATION OF MYOCARDIAL INFARCT SIZE IN HUMANS

Background-There are substantial amounts of cytoplasmic heart-type fat ty-acid-binding protein (FABP) (15 kDa) in myocardial tissue. The rapi d release of FABP into plasma during ischaemia indicates the possibili ty of using this protein as a biochemical marker for ischaemic myocard ial injury. Objective-To study the completeness of the release of FABP from damaged tissue in patients with acute myocardial infarction (AMI ) and the suitability of serial plasma FABP concentrations for estimat ion of myocardial infarct size. Methods-Immunochemically assayed FABP and enzymatically assayed creatine kinase isoenzyme MB (CK-MB) and alp ha-hydroxybutyrate dehydrogenase (HBDH) were determined serially in pl asma samples from 49 patients with AMI who had been treated with throm bolytic agents within six hours after the onset of AMI. Previously val idated circulatory models and a value of 2.6 h(-1) for the fractional clearance rate of FABP from plasma were used to calculate cumulative p rotein release into plasma. Results-Release of FABP was completed earl ier (24-36 h) after AMI than that of CK-MB (50-70 h) and that of HBDH (> 70 h). However, infarct size estimated from the cumulative release of the proteins and expressed as gram equivalents of healthy myocardiu m per Litre of plasma yielded a comparable value of 4-6 for both FABP and the two enzymes. Conclusion-The data indicate that FABP released f rom the heart after AMI is quantitatively recovered in plasma and that FABP is a useful biochemical plasma marker for the estimation of myoc ardial infarct size in humans.