MYOCARDIAL INFARCT SIZE CAN BE ESTIMATED FROM SERIAL PLASMA MYOGLOBINMEASUREMENTS WITHIN 4 HOURS OF REPERFUSION

Background. An early estimation of infarct size is useful for the appr opriate early treatment of patients with acute myocardial infarction. We evaluated how early and how accurately infarct size could be estima ted from serial plasma myoglobin (Mb) measurements in patients with su ccessful reperfusion. Methods and Results. We measured plasma Mb and c reatine kinase (CK) in 35 patients in whom reperfusion therapy was suc cessfully performed. Blood samples were collected at 15-minute interva ls for 2 hours after reperfusion, at 30-minute intervals for the subse quent 2 hours, and at 3-6-hour intervals until 52 hours after reperfus ion. Plasma Mb was measured by a newly developed turbidimetric latex a gglutination assay. Total Mb and CK release (SIGMAMb, SIGMACK) were ca lculated with a one-compartment model. The mean chord motion in the mo st hypokinetic 50% of the infarct-related artery territory was calcula ted from follow-up ventriculograms as an index of the severity of regi onal hypokinesis. There were significant correlations between SIGMAMb and SIGMACK (r = 0.89), between log SIGMAMb and the severity of region al hypokinesis (r = -0.85), and between log SIGMACK and the severity o f regional hypokinesis (r = -0.74). The time required for the cumulati ve Mb release curves to reach a plateau was 64 +/- 28 minutes. An addi tional 53 +/- 14 minutes was required to calculate the disappearance r ate constant of Mb, and 15 minutes was necessary for the assay. Theref ore, the total time required for SIGMAMb to be available was 132 +/- 4 0 minutes, significantly shorter than the time required for SIGMACK, 2 4.3 +/- 9.1 hours (p < 0.001). The infarct size could be estimated fro m the SIGMAMb in 34 of 35 patients within 4 hours of reperfusion. Conc lusions. Infarct size can be estimated accurately 4 hours after reperf usion by calculating the SIGMAMb in patients with successful reperfusi on.