Cardiac markers

Diagnosis of MI

The most serious type of ischemic injury is acute myocardial infarction (AMI). Transient and fully reversible myocardial ischemia is called angina pectoris . Clinical manifestations:

• Pain in the chest
• Changes on ECG
• Changes in biochemical markers

Classical tests in the diagnosis of MI

Test enzyme	Standard	The beginning of the rise	Maximum	Standardization	Multipler at maximum
Aspartate aminotransferase (AST)	< 0,67 μkat/l	4–8 h	16–48 h	3–6 days	Up to 25
Creatine kinase (CK)	men < 3,2 μkat/l	3–6 h	16–36 h	3–5 days	Up to 25
	women < 2,4 μkat/l
CK-MB isoenzyme	< 0,4 μkat/l, < 6 % of total CK activity
Lactate dehydrogenase(LD)	< 8 μkat/l	6–12 h	24–60 h	7–15 days	Up to 8
LD isoenzymes

New tests in the diagnosis of MI

Myoglobin, CK MB mass and Troponin, their serum levels during myocardial ischemia

Myoglobin

• cytoplasmic protein, source of O₂ in the anaerobic phase of contraction
• in the blood 0.5-2 h after MI (sensitivity 4-5 h)
• small molecule (Mr = 17,100), rapidly lost from the blood through the glomeruli
• standard

• M < 92 µg/l
• F < 76 µg/l

CK-MB mass isoenzyme (antigen determination)

• concentration is given in mass units (µg/l) !!
• degraded molecules also react to the antigen (higher sensitivity)
• standard: < 5 µg/l

Test enzyme	The beginning of the rise	Maximum	Standardization	Multiplier at maximum
Myoglobin	0,5–2 h	6–12 h	0,5–1 d	Up to 20
Troponin T	3,5–10 h	12–18 h (3–4 d)	7–20 d	Up to 300

Recommended procedure for biochemical examination in suspected AMI

First recruitment on admission - STATIM

• Basic parameters for broader differential diagnosis: Na, K, Cl, urea, creatinine, Ca, uric acid, cholesterol, TAG, total bilirubin, ALT, AST, ALP, GMT, LD, CRP
• Cardiac markers:

• CK, CK-MB
• Myoglobin – difficulties lasting 2-12 hours, normal renal function
• Troponin T:

• a) within 8 hours to exclude AMI
• b) after 12 hours to diagnose microinfarcts

Further recruitment

• 2. Recruitment in 6 ± 2 hours (CK, CK-MB, troponin T, Myoglobin)
• 3. Recruitment in 12 ± 2 hours (CK, CK-MB if the diagnosis or extent of involvement is not clear)
• 4. Recruitment in 24 ± 2 hours - exceptionally

Interpretation of results

Myoglobin

• < 30 µg/l

• normal in healthy, excludes AMI between 6 and 10 hour

• 30–70 µg/l

• if the concentration rises to less than 40 µg/l within 1 h, MI can be ruled out

• > 70 µg/l

• excluding skeletal muscle damage, MI

Troponin T

• < 0.05 µg/l - MI can be excluded, repeat in 10-12 h
• 0.05-0.1 µg/l - it is recommended to repeat testing in 1 hour
• 0.1-3 µg/l - myocardial damage
• > 3 µg/l - massive myocardial damage

Troponin I

• <0.1 µg/l - MI can be excluded
• 0.6-1.5 µg/l - according to the WHO this is evidence of MI

Confirmation of myocardial reperfusion

Analyze	Myocardial reperfusin
	Successful		Unsuccessful
	C1–C0 (µg/l)	Tmax–T0(h)	Tmax–T0(h)
Myoglobin	> 150	< 3	> 12
CK MBmass	> 10	< 8–12	> 12
Troponin T	> 0,2	< 14	> 14
Troponin I	> 100	< 14	> 14

Natriuretic peptides

Structure of BNP

• Hormones synthesized in atrial and ventricular cardiomyocytes
• Maintain electrolyte and volume homeostasis
• ANP, BNP - produced by cardiomyocytes
• CNP - produced by vascular endothelial cells and renal epithelium

Links

Related articles

• Cardiac markers in AMI

Resource

• MRAZOVA, K. Kardiomarkery [online]. [cit. 2012-03-15]. <https://el.lf1.cuni.cz/p67526721/>.