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Myocardial enzyme depletion in infarcted human hearts: infarct size and equivalent tissue mass
F H van der Veen1, R Visser, G M Willems
1Department of Biophysics, University of Linburg, Maastricht, The Netherlands.
Insights
Enzyme activity in heart tissue is altered in myocardial infarction, impacting infarct size estimates. However, specific enzyme correlations suggest plasma enzyme levels can still reflect myocardial injury.
Area of Science:
- Biochemistry
- Cardiology
- Pathology
Background:
- Accurate assessment of myocardial infarction (MI) size is crucial for patient management.
- Previous studies reported low correlations between enzymatic and histological methods for estimating infarct size.
- Understanding enzyme activity alterations in infarcted and non-infarcted myocardium is essential.
Purpose of the Study:
- To investigate myocardial enzyme activities in different heart tissue regions.
- To correlate enzymatic estimates with histological findings in myocardial infarction.
- To explore the phenomenon of 'diluted myocardium' and its impact on enzyme activity measurements.
Main Methods:
- Enzyme activities were measured in myocardial tissue sections from patients with acute MI, other cardiovascular disorders, and no known heart disease.
- Comparison of enzyme activities between infarcted and non-infarcted areas.
- Correlation analysis of residual myocardial enzyme activities.
Main Results:
- Both infarcted and non-infarcted myocardial tissue showed significantly altered enzyme activities.
- Low correlations were observed between enzymatic and histological infarct size estimations.
- A strong correlation was found between creatine kinase, alpha-hydroxybutyrate dehydrogenase, and aspartate aminotransferase activities.
- The 'diluted myocardium' phenomenon may explain observed pathological changes in enzyme activities.
Conclusions:
- Altered enzyme activities in both infarcted and non-infarcted tissue explain discrepancies in infarct size estimation.
- Despite alterations, plasma enzyme activities can still provide meaningful estimations of myocardial injury in gram equivalents of healthy myocardium.
- The findings support the utility of specific enzyme correlations for assessing myocardial damage.
Abstract:
Myocardial activities of several enzymes were measured in infarcted and non-infarcted areas of heart sections obtained from eight patients who died after acute myocardial infarction. Similar data were obtained from four patients with cardiovascular disorders who died from causes other than myocardial infarction and from six patients without previously known heart disease. It was found that both non-infarcted and infarcted tissue samples contained considerably altered enzyme activities. This finding explains the low correlations between enzymatic and histological estimates of infarct size previously reported. However, when the residual myocardial activities of different enzymes were compared with each other, a close correlation was found between creatine kinase, alpha-hydroxybutyrate dehydrogenase, and aspartate aminotransferase. It appears that the pathological changes in the myocardial activities of these enzymes may be explained by the phenomenon of diluted myocardium. This indicates that myocardial injury, as estimated from plasma enzyme activities, may still be expressed meaningfully in gram equivalents of healthy myocardium.