Cardiac enzymes are proteins and enzymes found within the heart muscle cells, and they help regulate their vital processes, such as muscle contraction and energy production.

When the heart muscle is exposed to factors such as excessive stress or injury, these enzymes begin to leak into the bloodstream, so they are measured to diagnose and monitor heart diseases, especially heart attacks. (1)

What are the types of cardiac enzymes?

Troponin is the most accurate and sensitive cardiac enzyme for detecting heart attacks and damage to the heart muscle.

There are other enzymes, but they are less accurate and less commonly used, including: (1)

• Cardiac creatine kinase CK-MB
• Myoglobin

Here is detailed information about these enzymes: (2)(3)

1. Troponin: 

Troponin is a protein in the heart muscle that contributes mainly to its contraction and consists of two main types: troponin T and troponin I.

In the event of a heart attack, troponin levels rise within 2-4 hours of its occurrence and remain elevated in the bloodstream for 7-14 days, despite the return of other indicators (enzymes) to their normal levels. This is what makes troponin the most accurate and important analysis.

2. Creatine Kinase CK-MB:

CK-MB levels begin to rise a few hours after a heart attack and return to normal within a day or two. This makes it less accurate than troponin, but it may be useful in diagnosing a recurrent heart attack within a short period.

3. Myoglobin:

Myoglobin is a muscle protein that stores oxygen in the muscles, including the heart muscle. Because it is found in all muscles, it is not specific to the heart; therefore, it is rarely used in the diagnosis of heart attacks.

What are the causes of elevated cardiac enzymes?

Cardiac enzymes rise when the heart muscle is damaged or stressed, and common causes include: (4)

• Heart attack: The most common cause of elevated cardiac enzymes, especially troponin.
• Myocarditis: Inflammation of the heart muscle, resulting from infection or autoimmune diseases.
• Pericarditis: Inflammation of the sac surrounding the heart.
• Acute heart failure: In severe cases, troponin levels may rise.
• Severe high blood pressure: Can put significant strain on the heart.
• Pulmonary embolism: A large clot in the lungs that affects heart function.
• Cardiac procedures and surgeries: Such as catheterization, open-heart surgery, or angioplasty may lead to a temporary rise in enzymes.
• Strenuous exercise or severe injuries: Rarely lead to elevated cardiac enzymes, but it may occur in professional athletes or due to chest injury.

How are they measured?

Cardiac enzymes are measured through blood tests, where tests are performed at successive intervals over several hours to monitor changes in their levels.

A final word...

If your blood tests show an elevation in cardiac enzymes, especially troponin, this may be an indication of stress or damage to the heart muscle, but not every elevation necessarily means a heart attack. However, it is a sign that requires attention and follow-up with a specialist doctor. For specialized consultation or for more information, you can book an appointment with us in the Cardiology Department.

References

1. Medscape - Cardiac Markers: Definition and Efficacy, Markers of Myocardial Necrosis and Ischemia, Acute Coronary Syndrome Testing Strategy
2. Healio - Cardiac Enzymes / Cardiac Biomarkers Topic Review | Learn the Heart
3. Oxford Academic - Myocardial Injury and the Release of Troponins I and T in the Blood of Patients | Clinical Chemistry
4. Testing.com - Troponin Test (cTN)