Heart disease remains the leading cause of death in the United States, claiming lives every 33 seconds and contributing to a significant economic burden.[1,2] For many, heart disease goes undetected until it's too late, with one in five heart attacks occurring without the victim's awareness. [3]
This article explores the importance of cardiac enzymes, also known as cardiac biomarkers. By understanding these biomarkers, individuals can take proactive steps to monitor and manage their heart health effectively.
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What Are Cardiac Enzymes?
Cardiac enzymes are also known as cardiac biomarkers. Enzymes are proteins that speed up chemical processes in the body.[4] When the heart muscle is damaged or stressed, cardiac enzymes are released into your bloodstream.[5] These levels are generally measured if there is a concern for damage or stress to the heart. Four primary cardiac enzymes are useful for detecting damage to the heart muscle.[6]
- Troponin T and troponin I – Troponins are the most sensitive markers for heart muscle injury. These are the preferred tests for evaluating a possible heart attack. Which test is used typically depends on which is available at the testing facility.[7]
- Creatinine kinase-MB (CKMB) – CKMB is an enzyme found in the heart muscle that was used as the primary marker for heart muscle injury before using troponin. It is not used as widely as previously because there are few situations where it adds more information than the troponin. It is also less sensitive and specific than troponins.[8]
- Myoglobin—Myoglobin is a protein released into the bloodstream when muscle is damaged. It is not specific to the heart muscle. Because of the non-specific nature of this protein, it’s no longer part of the specific guidelines for managing heart attacks.[9]
Understanding Elevated Cardiac Enzymes
Cardiac enzymes are generally measured to diagnose conditions associated with heart muscle damage, such as heart attacks. Elevation in these enzymes usually indicates that parts of the heart muscle have been injured. This injury can occur due to decreased blood flow, increased need for blood flow that the heart can’t respond to, or trauma.
Cardiac enzyme elevations may be mild or significant. Troponin, for example, may rise for 12 hours after injury. The degree of elevation may correlate with the amount of damage to the heart muscle.[7]
There are many reasons why the cardiac enzymes may be elevated. Causes of elevated cardiac enzymes include:[5]
- Myocardial infarction (heart attack)
- Myocardial ischemia (decreased blood flow to the heart without heart muscle death)
- Myositis (inflammation of the heart muscle)
- Heart Failure
- Strenuous exercise
- Pulmonary hypertension (elevated blood pressure in the lungs)
- Pulmonary embolism (blood clot in arteries to lung)
- Trauma to the heart muscle
- Medical procedures involving the heart (e.g., cardiac ablation, cardiac surgery)
- Kidney disease
- Certain medications (statins, steroids, chemotherapy drugs, etc.)
Lab Tests for Cardiac Enzymes
Testing for cardiac enzymes is accomplished through venipuncture (blood draw). The test involves putting a needle into the vein to collect a blood sample, which is then sent to the lab. An existing intravenous (IV) catheter may be used to draw the blood.
Cardiac enzymes are often drawn in a hospital or emergency department, though they can be ordered in any medical setting. If a heart attack is suspected, you may need to check serial labs, as it takes time for the enzymes to rise in the bloodstream in response to cardiac damage.
Additional Testing and Biomarkers
Additional testing might be needed in addition to cardiac enzymes. Electrocardiograms (ECG, EKG), echocardiograms, stress tests, and coronary angiography are other tests that can be used to assess heart function.
- An EKG is an electrical tracing of the heart rhythm that can identify abnormal heart rhythms and damage to the heart muscle, such as in a heart attack.[10] A heart attack is sometimes easy to see because there are ST segment elevations (STEMI). However, iIt is possible to have a heart attack with a normal EKG (this is called a non-ST elevation MI or NSTEMI). For this reason, EKG is combined with cardiac enzymes to evaluate for heart damage.
- An echocardiogram is an ultrasound of the heart. This test can be combined with a stress test to look for areas of the heart that do not move as well under conditions that would generally require increased blood flow to the heart muscle. An echocardiogram can also be used to assess how the heart is functioning.[11]
- A stress test evaluates how the heart functions and whether blood flow is adequate.[12] It can be performed using exercise or medications to increase the heart rate, thereby increasing the heart's oxygen demand and determining how well the body is able to respond to those increased demands.
- Coronary angiography is an invasive test that evaluates the blood flow through the arteries to the heart, heart function, and even pressure in the pulmonary arteries. This test is performed by putting a catheter in the groin and advancing it to the heart. Dye is then injected into the blood vessels and heart chambers to measure and evaluate it.[13]
Other lab tests that may also evaluate your heart function include B-type natriuretic peptide (BNP) and C-reactive protein (CRP). These tests can be used to assess stress on your heart. BNP is made in the blood vessels and heart.[14] It is elevated in conditions such as congestive heart failure. CRP is a marker of inflammation made in the liver. High-sensitivity CRP can help with evaluating the risk for heart disease and stroke.[15]
How Long Do Cardiac Enzymes Stay Elevated?
A normal range for cardiac enzymes depends on the assay being used.
- Troponin increases within two to three hours of a heart attack and usually peaks in 12-24 hours.[16] Troponin may stay elevated for several days after injury.
- CKMB may start to rise three to six hours after injury and peaks between 16 and 30 hours. CKMB usually resolves in 36 hours.[17]
- Myoglobin rises within two to three hours of muscle damage (not specific to the heart). It usually peaks 8 to 12 hours after injury.[18] It's important to note that myoglobin is not specific for heart damage. It can occur with any muscle damage, so it is more likely to be elevated after strenuous activity or a fall or other muscle trauma.
Even though it may take a while for cardiac enzymes to elevate, it is important to seek medical care immediately if someone experiences symptoms That could indicate damage to the heart muscle. The earlier that damage can be identified and treated, the better the outcome for most people.
The level of cardiac enzymes may vary depending on individual risk factors and conditions, such as kidney or liver disease. It may also correlate with the degree of damage in the heart.[19]
Management and Follow-Up
So, what happens if cardiac enzymes are elevated? Elevated cardiac enzymes, especially troponin, suggest damage to the heart muscle. This is a medical emergency and requires urgent evaluation. The management may depend on the duration of symptoms.
Certain types of heart attacks might result in an urgent trip to the cardiac catheterization lab for coronary angiography and the possible use of a balloon to open the blocked vessels and the insertion of a stent to keep them open. Other types of heart attacks might be managed with medication in a hospital setting. Nonheart attack forms of heart muscle damage may require other management strategies, such as medication.[20]
Long-Term Management
If you have been diagnosed with heart disease, your healthcare provider may recommend additional steps for long-term management of your health.
- Diet: The American Heart Association recommends a healthy diet and regular exercise to prevent and treat heart disease. A healthy diet includes a wide variety of fruits and vegetables, whole grains, healthy proteins, and healthy oils, and it also includes minimizing processed foods, sugars, and salt.
- Exercise: Ideally, 150 minutes of moderate exercise per week or 75 minutes of vigorous exercise per week is recommended.
- Smoking cessation: Another significant risk factor for heart disease is smoking, so smoking cessation is another step that people can take to improve their heart health.[21]
Regular Follow-Up
People diagnosed with heart disease or any other chronic health condition should have regular follow-ups and monitoring according to their healthcare provider's recommendations. Medications that may be used to treat heart disease include blood pressure medications, cholesterol medications, and, in some cases, blood thinners. The healthcare team may recommend other medications depending on the patient's risk factors.
Frequently Asked Questions (FAQs)
Some common questions that patients may have regarding cardiac enzymes include:
- What do cardiac enzymes show? Certain cardiac enzymes such as troponin, CKMB, and myoglobin are released in response to damaged muscle, especially in the heart. Elevations in these enzymes may indicate damage to the heart and require further evaluation and treatment.
- What cardiac enzymes indicate a heart attack? The phone and I and troponin T are most sensitive to cardiac injury. CKMB is another enzyme that may indicate heart disease but is less specific for heart damage. Myoglobin is released in response to muscle damage in other body parts besides the heart. It may indicate disease processes other than heart damage, such as muscle breakdown from strenuous exercise or injury from a fall.
- What do elevated cardiac enzymes mean for my health? Elevated cardiac enzymes are a sign of heart damage. This urgent medical condition should be evaluated in an acute medical care setting. Other biomarkers may indicate an increased risk for heart disease, such as high-sensitivity CRP.
Empowering patients to take control of their heart health and be proactive about their care is an important step in engaging them in the process of better health outcomes. If a patient is experiencing symptoms concerning heart disease, counseling them can be a balance between impressing upon them the urgency and importance of being evaluated while still helping them stay calm.
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Key Takeaways
- Cardiac enzymes such as troponin T, Troponin I, CK-MB, and myoglobin are tests that may indicate heart disease and damage and generally require urgent evaluation.
- Other healthcare conditions can influence cardiac enzymes, and levels may vary depending on the timing and extent of the damage.
- Lifestyle modifications such as diet, exercise, and smoking cessation can help prevent and treat heart disease.
- Being proactive about your health care is one of the best ways to ensure positive health outcomes. It is important to get routine screening tests as your health care team recommends and to educate yourself about your chronic health conditions and how best to manage them to be an informed advocate for your health. Talk to your healthcare provider about steps that you can take to mitigate your risk of heart disease and other chronic health conditions and for personalized recommendations specific to your health concerns.
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