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Detection of myocardial infarct extension by CK-B radioimmunoassay
Insights
Myocardial infarct extension, detected by a second rise in serum creatine kinase-BB (CK-B), occurred in 23% of patients. This phenomenon may be more common than clinically recognized, especially in anterior transmural myocardial infarcts.
Area of Science:
- Cardiology
- Biochemistry
Background:
- Myocardial infarct extension can occur after the acute event.
- Detecting infarct extension is crucial for patient outcomes.
Purpose of the Study:
- To define and quantify myocardial infarct extension using serum creatine kinase-BB (CK-B) measurements.
- To compare the incidence of infarct extension across different types of myocardial infarcts.
Main Methods:
- Serum CK-B levels were measured by radioimmunoassay every 12 hours for 14 days in 43 patients with acute myocardial infarcts.
- Patients were categorized into anterior transmural myocardial infarcts (AMI), inferior transmural myocardial infarcts (IMI), and subendocardial myocardial infarcts (SEMI).
Main Results:
- Infarct extension was detected in 23% of all patients.
- Extension occurred in 32% of AMI, 14% of IMI, and 20% of SEMI patients, with no statistically significant differences.
- Four patients with AMI and infarct extension died within 3 weeks; no increased mortality was observed in IMI or SEMI patients with extension.
Conclusions:
- Myocardial infarct extension is more common than clinically recognized, particularly when assessed with sensitive assays like CK-B.
- While extension was more frequent in AMI, the study did not find statistically significant differences between infarct types.
- Further research may be needed to compare these findings with methods like precordial mapping.
Abstract:
Myocardial infarct extension after the acute event was defined as a second reise in the myocardial isoenzyme of serum creatine kinase (CK-B) after the initial return of CK-B to normal values. In 43 patients with acute myocardial infarcts, CK-B was measured by radioimmunoassay every 12 hours for 14 days. Nineteen patients had anterior transmural myocardial infarcts AMI, 14 had inferior transmural myocardial infarcts (IMI) and 10 had subendocardial myocardial infarcts (SEMI). Infarct extension as detectd by a second rise in serum CK-B occurred in six patients (32%) with AMI, two (14%) with IMI and two (20%) with SEMI; these differences are not statistically significant. Infarct extension for all patients combined was 23%. Four patients with AMI also had infarct extension as determined by recurrent chest pain. ECG alterations and other enzyme changes. In the other six, the infarct extension was undetected clinically. Four patients with AMI and infarct extension died within 3 weeks after hospitalization. We did not note any additional morbidity or mortality in patients with infarct extension who had IMI or SEMI. There was no significant difference in the frequency of previous myocardial infarction, history of hypertension, diabetes mellitus or smoking history in patients with and without infarct extension shown by serum CK-B isoenzyme elevations. The measurement of serum CK-B values with a quantitative and sensitive assay suggests that myocardial infarct extension occurs more commonly than clinically recognized, but the frequency of extension may be less than that reported in patients in whom precordial mapping and total serum CK values were measured to identify this phenomenon.