18 November 2008
A monoclonal enzyme immunoassay for measuring human ventricular myosin light chain isotype 1 (HVMLC1) in serum has been developed. To evaluate the method in patients with suspected myocardial injury, we studied 51 patients (16 acute myocardial infarction (AMI), 19 unstable angina pectoris (UAP), 9 stable angina pectoris, 3 nonischemic heart disease, 4 hip surgery patients), and 190 controls (blood donors). Serial blood-samples were drawn from patients; a single blood-sample from controls. The diagnostic value of the HVMLC1 assay was compared with total creatine kinase (CK), CKMB activity, CKMB mass concentration, lactate dehydrogenase isoenzyme 1 (LD1), troponin T (TnT) and mitochondrial-aspartate aminotransferase (m-ASAT). The detection limit of HVMLC1 was 0.4 µg/l (linear range 0-20 µg/l). Sera from 190 reference persons did not contain detectable levels of HVMLC1 ( < 0.4 µg/l; 99% percentile). The coefficients of variation were 13% (1.0 µg/l) and 3.1% (17.7 µg/l). Cross-reactivity with myosin from skeletal muscle was seen. Times to peak value were: CK 19.3 ± 2.0, LD1 43.4 ± 3.2, HVMLC1 72.9 ± 7.0, and m-ASAT 67.3 ± 5.6 h. Time-curves of HVMLC1 and m-ASAT were similar, whereas time-curves for HVMLC 1 and TnT were quite different in most cases. Peak value of HVMLC 1 was five times higher than CK peak value and eight times that of LD1. HVMLC 1 appeared in the blood within hours after the onset of chest pain and in the majority remained for more than a week after AMI. Among patients with UAP 16% (3/19) had elevated HVMLC1 in serum, whereas elevated TnT was seen in 26% (5/19) and elevated CKMB mass in 26% (5/19). We conclude that the new HVMLC 1 assay offers a sensitive diagnosis of myocardial injury. It is characterized by a wide diagnostic time window. The similarity of the HVMLC 1 and m-ASAT curves indicates that it may be used to estimate the extent of myocardial necrosis.