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[MBCK and infarct size (author's transl)]
Insights
Calculating infarct size using creatine kinase (CK) and myoglobin-bound creatine kinase (MBCK) serum activity showed a moderate correlation. Variations in MBCK levels explain the discrepancies in infarct size estimations between the two methods.
Area of Science:
- Biochemistry
- Cardiology
- Clinical Chemistry
Context:
- Acute myocardial infarction (AMI) diagnosis and prognosis rely on accurate infarct size estimation.
- Creatine kinase (CK) and its isoenzymes, like myoglobin-bound creatine kinase (MBCK), are biomarkers for myocardial injury.
- Assessing infarct size using serum enzyme activity requires understanding the behavior of these enzymes post-infarction.
Purpose:
- To evaluate the correlation between infarct size calculated from serum CK activity (CK-IG) and MBCK activity (MBCK-IG) in patients with acute myocardial infarction.
- To investigate the factors contributing to discrepancies in infarct size estimations using CK and MBCK.
- To assess the reliability of MBCK as a sole marker for infarct size calculation.
Summary:
- In 128 acute myocardial infarction patients, infarct size was calculated using CK and MBCK serum activity with individual fractional decay rates.
- A moderate correlation (r=0.65) was observed between CK-IG and MBCK-IG, with slight improvement upon excluding resuscitated patients (r=0.69).
- Discrepancies are attributed to wide variations (4.7-21.2%) in the serum MBCK to CK percentage, deviating from the assumed myocardial 14% constant.
Impact:
- Highlights the limitations of using MBCK alone for infarct size calculation due to variable serum enzyme ratios.
- Suggests that the assumption of a constant MBCK percentage in serum is invalid, impacting the accuracy of infarct size estimations.
- Underscores the need for refined methodologies or consideration of enzyme variations when calculating infarct size from serum biomarkers.
Abstract:
In 128 patients (20 f., 98 m., age between 26 and 88 years, mean age 59 years) with acute myocardial infarction, infarct size was calculated from CK and MBCK serum activity using the individual fractional decay rate kD. Only a moderate correlation could be found between infarct size calculated from CK-serum curves (CK-IG) and from MBCK (MBCK-IG) (r = 0.65). Only little improvement was achieved by excluding those patients who had been resuscitated (n = 13, r = 0.69). In 20% of the patients there was a good correlation (+/- 5 g eq) between CK-IG and MBCK-IG. In 14% MBCK-IG was larger and in 66% smaller than CK-IG. Calculation of MBCK-IG is based on a constant MBCK percentage of CK in myocardium, namely 14%, and assumes that the distribution volume and amount of enzyme released into the serum is the same for CK and MBCK. Thus the percentage of MBCK in serum compared to CK should also be 14%. We found an average value approaching this (13.6%), but with a wide range between 4.7 and 21.2%. It is this variation which is responsible for the poor correlation between both IGs.