Cardiac Markers

Cardiac Markers, also known as cardiac biomarkers or cardiac enzymes, are substances or proteins that are released into the bloodstream when the heart is damaged or stressed. They are essential tools in the diagnosis, prognosis, and monitoring of various cardiac conditions, particularly acute coronary syndromes (ACS) like heart attacks (myocardial infarctions) and other heart-related diseases.

There are many types of cardiac markers:

• Myoglobin
• Troponin T
• Troponin I
• CK-MB
• LDH
• AST(SGOT)
• NT-Pro BNP

Characteristics of ideal cardiac marker

• Cardiac-specific, Sensitive
• Easy to Measure
• Absent (Trace) in blood normally
• Not expensive
• Release rapidly after myocardial injury

Explanation of Cardiac Markers:

1. Myoglobin

• Myoglobin is a protein present in the heart and skeletal muscles. It increases the rate of transport of O2 within the muscle cells during construction.
• An increase in serum myoglobin occurs after trauma to skeletal or cardiac muscle as in crush injury. 

Time sequence

Onset: 30 hr.

Peak: 2-4 hr.

Fall: 1 day

• Rises rapidly
• Sensitive Marker
• Non-Specific- Also increase in skeletal muscle

Normal Range – 25-72 ng/ml

2. Troponin

Troponin is a protein present in the heart and skeletal muscles.

There are 3 types

• Troponin C ( cardiac and skeletal muscles)
• Troponin T ( cardiac muscles)
• Troponin I ( cardiac muscles)

Troponin I, T is particular and sensitive to cardiac and therefore is known as cardiac troponin.

Troponin T is thought to be a more specific marker of cardiac damage than Troponin T.

Time sequence

Onset: 2-4 hr.

peak: 12-24 hr

Fall: 10 day

• Particular Marker
• Rise early
• Late Marker

1. Normal range Troponin I 0-0.04ng/ml
2. Troponin T 0-0.01 ng/ml

3. CK-MB

Creatinine Kinase is an enzyme present in the heart, Skeletal muscle, and brain.

Isoenzymes of CK

There are 3 isoenzymes of CK

• CK-MM- Skeletal Muscle
• CK-MB- Heart Muscle
• CK-BB – Brain, GT tract

It provides energy during muscle contraction.CK-MB is used for diagnosing a heart attack.

Time Sequence

• Onset 24 hr
• Peak 6-10 hr
• Fall 3 days

CK-MB is very Specific. It rises early and is good for early diagnosis.

4. AST( Aspertat transminase) or SGOT

AST is present in high concentrations in cells of the cardiac, liver, kidney, Skeletal muscle, and RBCs.

Time Sequence

• Onset 6-8 hr
• Peak 24-48 hr
• Fall 4-6 day

Normal Range of AST: 8-10 IU/ L

5. LDH (Lactate Dehydrogenase )

LDH is an enzyme found in heart, Skeletal muscle, brain, and liver blood cells.

Isoenzymes of LDH

• LDH – 1 ( heart)
• LDH – 2 ( blood )
• LDH – 3, LDH – 4 and LDH – 5

Normally, LDH -2 is higher than LDH – 1, but in Acute Myocardial infarction the LDH -1 increases over LDH -2 in serum this is called FLIPPED PATTERN.

1. First marker used for Myocardial infarction.

2. Not a good marker as it increases late.

3. Need electrophoresis to determine a Flipped pattern. 

Time Sequence

• On set 12-24 hr
• Peak 1-2 days
• Fall 3-5 days

6. NT – Pro BNP

N Terminal pro B – type natriuretic peptide

1. NT Pro BNP is mainly synthesized in cardiac muscle in the left ventricle ( LV ) as a response to the myocytes of the ventricle.
2. High levels can mean your heart is not pumping as much blood as your body needs.
3. Heart failure

Normal range: Less than 125 pg/ml <74 years

Less than 450pg/ml >75 years

Why do I need a Cardiac Markers Test:

Here are some reasons why you might need a Cardiac Markers Test:

1. Chest Pain or Discomfort: If you are experiencing chest pain, pressure, or discomfort, a Cardiac Markers Test may be ordered to determine whether you are having a heart attack or angina. Elevated levels of certain cardiac markers can indicate heart muscle damage.
2. Monitoring Heart Conditions: If you have a known heart condition, such as a history of heart attacks or heart surgery, your doctor may order cardiac marker tests regularly to monitor your heart’s health and assess the effectiveness of your treatment.
3. Assessment of Risk Factors: Cardiac markers can also be used to assess your risk of heart disease. Your doctor may order these tests as part of a routine health checkup, especially if you have risk factors such as a family history of heart disease, high blood pressure, high cholesterol, smoking, or diabetes.
4. Evaluation of Symptoms: If you have symptoms such as shortness of breath, fatigue, or dizziness that could be related to heart problems, your healthcare provider may recommend cardiac marker tests to help diagnose or rule out heart issues.
5. Post-Cardiac Event: After a heart attack or other cardiac event, cardiac markers can be used to assess the extent of heart muscle damage and guide treatment decisions.
6. Medication Monitoring: Some medications used to manage heart conditions can affect cardiac marker levels. Regular testing may be necessary to ensure that medications are dosed appropriately and are not causing harm.
7. Risk Stratification: Cardiac marker tests can help doctors stratify patients into risk categories. For example, elevated cardiac markers in the absence of other symptoms might indicate a higher risk of future heart problems.
8. Evaluation of Treatment Response: If you are undergoing treatment for a heart condition, cardiac marker tests can be used to assess how well you are responding to treatment and whether any adjustments are needed.

It’s important to note that there are different cardiac markers, including troponin, creatine kinase-MB (CK-MB), and myoglobin, among others. The choice of which markers to test for and when to perform the tests depends on your specific clinical situation and the judgment of your healthcare provider.