Cardiac Profile Test

Table of Contents

Introduction

A cardiac profile test is a comprehensive panel of blood tests designed to evaluate the heart’s overall health and detect any risk factors associated with cardiovascular diseases.
It plays a crucial role in the early diagnosis, monitoring, and management of conditions such as coronary artery disease, myocardial infarction, and heart failure.
This profile typically includes key biomarkers such as lipid profile (total cholesterol, LDL, HDL, triglycerides), cardiac enzymes (like CK-MB, troponins), and inflammatory markers (such as C-reactive protein). Some advanced panels may also assess homocysteine levels, NT-proBNP, and lipoprotein (a), among others.
By analyzing these parameters, clinicians can assess the extent of cardiac stress, inflammation, and the likelihood of atherosclerosis or ischemic events, enabling timely medical intervention and lifestyle modifications to prevent serious cardiac outcomes.

Lipid Profile
- Total Cholesterol – Measures the overall cholesterol in the blood.
- LDL Cholesterol (Low-Density Lipoprotein) – “Bad” cholesterol contributing to plaque buildup in arteries.
- HDL Cholesterol (High-Density Lipoprotein) – “Good” cholesterol that helps remove excess cholesterol from the blood.
- Triglycerides – Type of fat (lipid) in the blood; elevated levels increase heart disease risk.
- VLDL (Very Low-Density Lipoprotein) – Transports triglycerides; linked with atherosclerosis.
Cardiac Enzymes & Biomarkers
- Troponin I or T – Highly specific and sensitive markers of myocardial injury (heart attack).
- Creatine Kinase-MB (CK-MB) – Enzyme found in the heart; elevated in myocardial damage.
- Total CPK (Creatine Phosphokinase)
- Myoglobin – Early marker of muscle injury, including cardiac muscle.
- SGOT – (AST – Aspartate Aminotransferase)
- LDH – (Lactate Dehydrogenase)
Inflammatory Marker
- High-Sensitivity C-Reactive Protein (hs-CRP) – Indicates low-grade inflammation associated with cardiovascular risk.
Brain Natriuretic Peptide (BNP) or NT-proBNP
- Used to assess and monitor heart failure severity.
Homocysteine
- Elevated levels are linked to increased risk of coronary artery disease.
Lipoprotein (a)
- Genetic lipid marker associated with early atherosclerosis and cardiovascular events.
Electrolytes and Minerals
- Potassium, Sodium, Calcium, and Magnesium – Help evaluate cardiac function and rhythm disturbances.

Cardiac Enzymes & Biomarkers

Total Creatine Phosphokinase

Principle

Creatine Phosphokinase (CPK or CK) catalyzes the reversible transfer of a phosphate group from creatine phosphate to ADP, forming ATP and creatine:

$Glucose-6-phosphate + NADP^{+} G6PD 6-Phosphogluconate + NADPH + H^{+}$

The increase in NADPH concentration is directly proportional to CPK activity and is measured colourimetrically at 340 nm.

Method

Colourimetric

Type

Enzymatic assay

Sample Material

Specimen: Serum (preferred) or plasma (heparinized)
Collection: Avoid hemolysis (RBCs contain enzymes that interfere)
Storage: Analyze within a few hours; if delayed, refrigerate at 2–8°C (stable for 24 hours)

Normal Reference Range

Male: 38–174 U/L
Female: 26–140 U/L

Requirements

Colorimeter or spectrophotometer (set at 340 nm)
Water bath (37°C)
Test Tube
Stop watch
Micropipettes

Reagents

Imidazole buffer, pH 6.1	125 mmol/l
Glucose	25 mmol/l
Magnesium acetate	12.5 mmol/l
EDTA	2 mmol/l
N-acetylcysteine	25 mmol/l
NADP	2.4 mmol/l
Hexokinase	> 6.8 U/ml

ADP	15.2 mmol/l
D-glukoso-6-phosphate-dehydrogenase	> 8.8 U/ml
Creatine phosphate	250 mmol/l
AMP	25 mmol/l
Diadenosine pentaphosphate	103 μmol/l

Procedure

Reagent 1 (buffer)	1.000 ml
Sample	0.050 ml

Mix and incubate for 3 min. at 37°C. Then add:

Reagent 2 (substrate)

0.250 ml

Mix and incubate for 3 min. at 37 °C. Then, measure the absorbance and, at the same time, start the stopwatch. Read the absorbance again exactly after 1, 2 and 3 minutes. Calculate the average 1-minute absorbance change (ΔA).
Monoreagent method – sample start

Working solution	1.000 ml
Sample	0.040 ml

Mix and incubate for 3 min. at 37 °C.

Calculation

CPK (U/L)=ΔA/min×F(F = factor provided by manufacturer)

Principle of Troponin Test

Troponins are regulatory proteins involved in calcium-mediated muscle contraction. The cardiac troponin complex has three subunits:

Troponin C (TnC) – binds calcium
Troponin I (TnI) – inhibits actin-myosin interaction
Troponin T (TnT) – binds the complex to tropomyosin

In cardiac muscle:

cTnI and cTnT have unique amino acid sequences, distinct from skeletal muscle isoforms.
During myocardial injury, especially acute myocardial infarction (AMI), cardiac cell membranes are disrupted, leading to leakage of intracellular contents, including troponins, into the circulation.

Detection:

The test is based on antibody-antigen interactions, where monoclonal or polyclonal antibodies specific to cTnI or cTnT are used.
The amount of troponin detected reflects the extent of myocardial injury.

Sample Type and Collection

Sample: Venous blood
Preferred tube: Serum (red-top) or plasma (lithium heparin or EDTA)
Storage:
- Room temperature: up to 8 hours
- Refrigerated (2–8°C): up to 24 hours
- Frozen (−20°C or below): longer storage

Timing:

Troponins begin to rise: 3–6 hours after injury
Peak levels: 12–24 hours
Remain elevated: 7–10 days (cTnT may persist longer than cTnI)

Methods Used

A. Immunoassay-Based Methods (Routine clinical use)

Enzyme-Linked Immunosorbent Assay (ELISA)
- Sandwich-type assay using capture and detection antibodies.
- Signal is proportional to troponin concentration.
Chemiluminescent Immunoassay (CLIA)
- Uses a chemiluminescent label that emits light during a reaction.
- Higher sensitivity and automation.
Fluorescence Immunoassays (FIA)
- Fluorescent tags emit signals read by detectors.
High-Sensitivity Troponin Assays (hs-cTn)
- Can detect troponin levels in picogram/mL range
- Allows early diagnosis (within 1–2 hours)

B. Point-of-Care Testing (POCT)

Rapid immunochromatographic tests
Useful in ER or ambulance settings
Less sensitive but faster (results in ~15 min)

C. Mass Spectrometry (Research Use)

High specificity and multiplexing ability
Rarely used in routine settings due to complexity

Clinical Significance:

Diagnosis of Myocardial Infarction (MI):
- Troponin levels rise within 3–6 hours, peak at 12–24 hours, and may remain elevated for 7–10 days.
- High-sensitivity assays can detect very early myocardial injury.
Differential Diagnosis of chest pain
Prognostic marker in:
- Unstable angina
- Heart failure
- Pulmonary embolism
- Sepsis-related cardiac injury
Risk stratification in cardiac patients

Creatine Kinase MB

Principle

Creatine phosphate + ADP —–^{CKBB / CKMB}——> Creatine + ATP

ATP + Glucose——^HK———-> Glucose-6-phosphate + ADP

Glucose-6-phosphate + NADP—–^G6PDH—–> Gluconate-6-P + NADPH + H⁺

Method

Enzymatic method

Sample

Serum free of hemolysis, heparinized plasma, protected from light. Stability
24 hrs. at 2-8°C; 3 days at -20°C

Reagents

Reagent I: Buffer Reagent I
Reagent II: Enzyme Reagent II

Procedure

Working Reagent

1000 µl

Incubate at Assay temperature for 1 min and add.

Sample

50 µl

Mix well and after 5 min. measure the change in absorbance. Read the initial absorbance and start timer simultaneously, read again after every 60 seconds for 5 minutes. Calculate ∆ A/min.

Calculation

U/l CKB = ∆ A/min. x 6752

Lactate dehydrogenase

Principle

Kinetic determination of lactate dehydrogenase according to the following reaction.

Pyruvate + NADH + H⁺———-^LDH———> L-Lactate +NAD⁺

Method

Optimized UV-test according to IFCC

Sample

Serum or heparin plasma or EDTA plasma. Separate at the latest 1h after blood collection from cellular contents.
1 month at 4 – 8°C
Discard contaminated specimens

Reagents

Reagent I: Buffer reagent
Reagent II: Substrate reagent

Procedure

Working Reagent	1000 μl
Sample	25 μl

Mix well and after 1 min incubation, measure the change in absorbance per min. (ΔA/min.) for next 2 minutes.

Calculation

LDH Activity (IU/L) = Δ A/min x 6592

SGOT (AST – Aspartate Aminotransferase)

CLICK HERE FOR MORE INFORMATION ——> SGOT

Cardiac Profile Test

Introduction