A heart attack (myocardial infarction) usually occurs when a blood clot blocks blood flow to the heart. Without blood, tissue loses oxygen and dies. A heart attack is a medical emergency.
The symptoms of a heart attack are as follows.
• Pain or discomfort in the chest, such as a squeezing sensation or feeling of fullness
• Pain in the neck, back, left arm, or jaw
• Shortness of breath
• Light-headedness or dizziness
• Nausea or vomiting
• Sudden sweating
• Tiredness
Cardiac biomarkers include enzymes, proteins and hormones which show up in the blood when the heart is under severe stress or due to lack of proper oxygenation to the heart. These markers are tested to understand the severity of the heart attack or how seriously the heart has been affected. These biomarkers indicate if someone has suffered a heart attack currently or very recently.
Cardiac troponin
Cardiac troponin is a protein and is the most commonly used cardiac biomarker with very high sensitivity. Troponin is released into the bloodstream soon after a heart attack. It also stays in your bloodstream days after all other related biomarkers go back to normal levels. Two forms of troponin may be measured: troponin T and troponin I. Troponin I is highly specific to the heart and stays higher longer than another commonly used biomarker – creatinine kinase-MB. Current guidelines from the American Heart Association (AHA) say Cardiac troponin I is the best biomarker for finding a heart attack.
Creatinine kinase (CK)
This is an enzyme that can also be measured several times over a 24- hour period of a suspected heart attack. It will often at least double if you’ve had a heart attack. But because levels of CK can go up in many other conditions besides a heart attack, it is not a very specific marker for heart attack. Other conditions that contribute to elevated CK levels are kidney failure, trauma due to surgery, inflammation, etc.
CK-MB
This is a subtype of CK. It is more sensitive to finding heart damage from a heart attack. CK-MB rises 4 to 6 hours after a heart attack. But it is generally back to normal in a day or two. Because of this, it’s not very helpful when a healthcare provider is trying to figure out if your recent chest pain was a heart attack. Also, there is no correlation between the severity of heart attack and CK-MB levels. To help differentiate heart attack from skeletal muscle damage, a CK index can be calculated using CK-MB and total CK as follows: CK index = (CK-MB, ng/mL) x100 / (total CK activity, IU/L). If CK-MB is elevated and the CK index is higher than 2.5 to 3.0, heart damage is likely.
Myoglobin
This is a small protein that stores oxygen. It is seen in the heart and skeletal muscles and is measured occasionally as suggested by the physician. Myoglobin is sometimes measured in addition to troponin to help diagnose a heart attack. It is also not very specific for finding a heart attack. Myoglobin increases in your blood 2 to 3 hours after the first symptoms of muscle damage.