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Infarct size estimation from serial CK MB determinations: peak activity and predictability
Abstract:
In 198 patients with acute myocardial infarction serial measurements of plasma creatine kinase isoenzyme MB (CK MB) were performed at four hour intervals. In every patient, maximal CK MB activity (peak activity) was compared with calculated total release per litre plasma. In 28 patients (group 1) sufficient plasma samples were available for calculation of the apparent first order inactivation constant kd. Mean apparent kd in group 1 patients was 0 . 085 +/- 0 . 018 h-1 (mean +/- SD). Total release in group 1 was calculated with individual apparent kd values (Q) and with the mean kd value (Q*). In the remaining 170 patients (group 2), Q* only was calculated. A linear relation between peak activity P and total release (both Q and Q*) was found, extending over the whole range of CK MB peak activities that are routinely observed (4-216 U/l). It was immaterial whether a one or a two compartment model was used: both yielded a close linear relation. Though the mean ratio between Q* and peak activity depends on the value of kd chosen for calculation of total release (the ratio increasing with increasing kd), linearity between peak activity and Q* was found for any value of kd up to 0 . 4 h-1. In group 1, shapes of calculated CK MB release curves Q*(t), expressed relative to maximal release Q(40), were sufficiently similar so as to be superimposable; the section of the release curves extending from 12 hours before until two hours after peak time could be tentatively described by a linear time course with a slope of 4 . 2 +/- 0 . 5% per hour (mean +/- SD). We conclude that peak activity of CK MB is a reliable estimate of cumulative CK MB release and may be clinically more practicable than calculation of Q(40). Both the similarity and the large apparently linear section of the calculated enzyme release curves possibly permit early prediction of Q(40), with acceptable precision.
Insights
Peak creatine kinase MB activity reliably estimates total enzyme release in acute myocardial infarction patients. This finding offers a more practical clinical approach than complex release calculations for diagnosing heart attacks.
Area of Science:
- Biochemistry
- Cardiology
- Clinical Diagnostics
Background:
- Acute myocardial infarction (AMI) diagnosis relies on cardiac enzyme markers.
- Creatine kinase isoenzyme MB (CK MB) is a key biomarker for myocardial damage.
- Accurate quantification of CK MB release is crucial for assessing infarct size.
Purpose of the Study:
- To evaluate the reliability of peak plasma CK MB activity as an estimate of total CK MB release in AMI patients.
- To determine the clinical practicability of using peak CK MB activity compared to complex release calculations.
Main Methods:
- Serial plasma CK MB measurements at 4-hour intervals in 198 AMI patients.
- Calculation of apparent first-order inactivation constant (kd) in a subgroup of 28 patients.
- Comparison of peak CK MB activity with calculated total release (Q and Q*) using individual and mean kd values.
Main Results:
- A strong linear relationship was observed between peak CK MB activity and calculated total CK MB release (Q and Q*) across a wide range of activities.
- This linearity was consistent regardless of whether a one or two-compartment model was used and for kd values up to 0.4 h-1.
- Calculated CK MB release curves showed similarity, suggesting potential for early prediction of total release (Q(40)) with acceptable precision.
Conclusions:
- Peak CK MB activity serves as a reliable and clinically more practicable estimate of cumulative CK MB release in AMI.
- The linear relationship and similarity of release curves support the use of peak activity for clinical assessment.
- Early prediction of total CK MB release may be feasible using these findings.