Cardiac Biomarkers

Cardiac biomarkers are enzymes, proteins, and hormones that are associated with heart function, damage or failure. Some of the tests are specific for the heart while others are also elevated with skeletal muscle damage. Cardiac biomarkers are used for diagnostic and prognostic purposes and are frequently ordered by caregivers when someone comes into the Emergency Room complaining of symptoms, such as chest pain, pressure, nausea, and shortness of breath. These tests are ordered, along with other laboratory and non-laboratory tests, to detect heart failure (which is often a chronic, progressive condition affecting the ability of the heart to fill with blood and pump efficiently) and the acute coronary syndromes (ACS) as well as to help determine prognosis for people who have had a heart attack. ACS is a group of symptoms that reflect a sudden decrease in the amount of blood and oxygen, also termed 'ischemia,' reaching the heart. This decrease is frequently due to either a narrowing of the coronary arteries (atherosclerosis or vessel spasm) or unstable plaques, which can cause a blood clot (thrombus) and blockage of blood flow. If the oxygen supply is low, it can cause angina (pain); if blood flow is reduced, it can cause death of heart cells (called myocardial infarction or heart attack) and can lead to death of the affected heart muscle cells and to permanent damage and scarring of the heart.

The goal with cardiac biomarkers is to be able to detect the presence and severity of an acute heart condition as soon as possible so that appropriate treatment can be initiated.

There are only a few cardiac biomarkers that are being routinely used by physicians. Some have been phased out because they are not as specific as the marker of choice – troponin. Many other potential cardiac biomarkers are still being researched but their clinical utility has yet to be established.

Note: Cardiac biomarkers are not the same tests as those that are used to screen the general healthy population for their risk of developing heart disease. Those can be found under Cardiac Risk Assessment.

LABORATORY TESTS CURRENT CARDIAC BIOMARKERS

  • CK and CK-MB

  • BNP or (NT-proBNP)

  • Troponin

  • Myoglobin (not always used; sometimes ordered with troponin)

MORE GENERAL TESTS FREQUENTLY ORDERED ALONG WITH CARDIAC BIOMARKERS

  • Blood Gases

  • CMP

  • BMP

  • Electrolytes

  • CBC

ON THE HORIZON

Ischemia modified albumin (IMA) – Test has received FDA approval for use with troponin and electrocardiogram to rule out acute coronary syndrome (ACS) in patients with chest pain. May become useful for identifying patients at higher risk of heart attack and potentially could replace myoglobin one day.

NON-LABORATORY TESTS

These tests allow caregivers to look at the size, shape, and function of the heart as it is beating. They can be used to detect changes to the rhythm of the heart as well as to detect and evaluate damaged tissues and blocked arteries.

  • EKG (ECG, electrocardiogram)

  • Coronary angiography (or arteriography)

  • Stress testing

  • Nuclear scan

  • ECG (echocardiogram)

  • Chest X-ray

THE FOLLOWING SUMMARIZES CURRENTLY USED CARDIAC BIOMARKERS.

Marker: CK

  • What: Enzyme that exists in three different isoforms

  • Where Found: Heart, brain, and skeletal muscle

  • What Indicates: Injury to muscle cells

  • Time to Increase: 4 to 6 hours after injury, peaks in 18 to 24 hours

  • Time back to Normal: Normal in 48 to 72 hours, unless due to continuing injury

  • When/How Used: Being phased out, may be ordered prior to CK-MB

Marker: CK-MB

  • What: Heart- related portion of total CK enzyme

  • Where Found: Heart primarily, but also in skeletal muscle

  • What Indicates: Injury (cell death) to heart

  • Time to Increase: 4 to 6 hrs after heart attack, peaks in 12 to 20 hours

  • Time back to Normal: Returns to normal in 24 to 48 hours unless new/continual damage

  • When/How Used: Not as specific as Troponin for heart injury/attack, may be ordered when Troponin is not available, may be ordered to monitor new/continuing damage

Marker: Myoglobin

  • What: Small oxygen-storing protein

  • Where Found: Heart and other muscle cells

  • What Indicates: Injury to heart or other muscle cells. Also elevated with kidney problems.

  • Time to Increase: Starts to rise within 2 to 3 hours, peaks in 8 to 12 hours.

  • Time back to Normal: Falls back to normal by about one day after injury occurred

  • When/How Used: Ordered along with Troponin, helps diagnose heart injury/attack

Marker: Cardiac Troponin

  • What: Components of a Regulatory protein complex. Two cardiac specific isoforms: T and I

  • Where Found: Heart muscle

  • What Indicates: Heart injury/damage

  • Time to Increase: 4 to 8 hours

  • Time back to Normal: Remains elevated for 7 to 14 days

  • When/How Used: Ordered to help assess prognosis and diagnose heart attack

Marker: LDH

  • What: Enzyme

  • Where Found: Almost all body tissues

  • What Indicates: General marker of injury to cells

  • When/How Used: Phased out, not specific

Marker: AST

  • What: Enzyme

  • Where Found: Almost all body tissues

  • What Indicates: General marker of injury to cells

  • When/How Used: Phased out, not specific

Marker: Hs-CRP

  • What: Protein

  • Where Found: Associated with athero-sclerosis

  • What Indicates: Inflammatory process

  • Time back to Normal: Elevated with inflammation

  • When/How Used: May help determine prognosis of patients who have had heart attack

Marker: BNP

  • What: Hormone

  • Where Found: Heart's left ventricle

  • What Indicates: Heart failure

  • Time back to Normal: Elevation related to severity

  • When/How Used: Help diagnose and evaluate heart failure, prognosis, and to monitor therapy