Heart Attack and Acute Coronary Syndrome and Laboratory Tests

 Also referred to as an acute myocardial infarct, a heart attack occurs when an artery blockage prevents blood from flowing to a portion of a person’s heart. If someone isn’t treated swiftly, heart tissue can be damaged or even destroyed. A heart attack can be fatal. The American Heart Association states that each year, approximately 735,000 people in the United States experience heart attacks. Around 120,000 of those people do not survive.  

The symptoms and signs that are linked with insufficient blood flowing to the heart are referred to as Acute coronary syndrome (ACS). What separates a heart attack from other types of ACS is that the decrease in blood flows continues, which causes heart muscle cells to be damaged or destroyed. If someone is brought into the ER, healthcare workers need to run tests to see if the symptoms are being caused by a heart attack or something else.  

The human heart is an organ that’s primarily made from cardiac muscle. It uses a system of arteries and veins to pump blood through the body. As blood flows through the human body, it picks up oxygen from the lungs. The blood then passes through the pulmonary veins and enters the heart. The blood is then pumped out, bringing oxygen to the tissues. The veins return the blood to the heart, where it is pumped back out to collect more oxygen from the lungs. The heart is unable to carry out these tasks without a significant amount of oxygen, which is obtained from the heart’s network of arteries and veins.  

In most cases, a blockage that leads to a heart attack occurs because of a blood clot in a coronary artery, which are the arteries that bring blood to the heart. This is more likely to happen when the walls of the arteries are thickened and narrowed. This happens via a process known as atherosclerosis, which causes plaque to gradually build up on artery walls. If a clot in a coronary artery keeps blood from flowing to the heart for more than an hour, it can cause scarring in that area. Furthermore, it can cause heart muscle cells to die.  


Several factors can increase the risk of a heart attack, such as: 

  • High cholesterol  
  • High blood pressure  
  • Obesity  
  • A sedentary lifestyle  
  • Diabetes  
  • Advanced age  
  • A smoking habit  
  • History of heart disease in the family  
  • Drug use  
  • Stress  
  • Autoimmune conditions like rheumatoid arthritis or lupus  
  • Pre-eclampsia, which is linked with high blood pressure in pregnancy  

Symptoms and Warning Signs  

Heart attacks and other types of acute coronary syndrome often cause abrupt pain in the chest. The pain frequently radiates into other parts of the body, such as the arm, shoulder, or jaw, and does not go away with rest. In some cases, this is a more intense version of pain that’s reoccurring, but in other cases, people are experiencing this pain for the first time.  

If someone has already experienced chest pain because their narrowed arteries do not allow an adequate amount of blood to flow to the heart, they may find that these symptoms are more intense or last for a longer period of time.  

It should be noted that not all people that have heart attacks experience this symptom. It is more likely that women will experience atypical symptoms. Women often experience milder symptoms, which means these symptoms are frequently attributed to another cause. It’s possible for a heart attack to occur abruptly, but it’s also possible for symptoms to slowly build up over time. In some cases, people may find that their symptoms stop and then return.  

Some common signs and symptoms are:  

  • Discomfort, pain, or pressure in the chest (this is the most common symptom)  
  • Elevated heart rate or skipping a heartbeat  
  • Stomach pain, nausea, and vomiting  
  • Shortness of breath or difficulty breathing  
  • Sweating  
  • Lightheadedness  
  • Fatigue  
  • Blood pressure changes  
  • Pain in the arms, back, neck, or jaw  

It’s possible for people to experience these symptoms without feeling any chest pain, especially if they’re older or diabetic.  

Testing for A Heart Attack  

If a patient arrives at the ER showing acute coronary syndrome symptoms, it’s not always immediately clear that they are experiencing a heart attack. Their chest pain could have another cause, or they may be dealing with unstable angina. Thankfully, there is a range of tests that allow healthcare workers to determine whether a heart attack has taken place.  

Laboratory Tests  

Typically, it’s necessary to run a blood test to determine whether someone has suffered a heart attack. When muscle cells are damaged, certain proteins are released. To see if a patient has suffered a heart attack, cardiac biomarkers are ordered, such as: 

Troponin: This is the marker that is most frequently ordered. It’s focused on the heart. Troponin blood levels are going to be elevated in the hours after heart damage has occurred. These levels can remain elevated for as long as two weeks. If a patient arrives in the emergency room showing acute coronary syndrome symptoms, troponin tests will likely be ordered right away. Over the next few hours, these tests will be ordered a few more times so that concentration changes can be monitored. If the tests show normal levels, stable angina is likely causing the pain, not heart muscle damage. However, if the results show levels rising or falling, it’s a clear indicator of a heart attack.  

A high-sensitivity troponin test is like the standard test, but it can detect this protein at lower levels. Since this is a more sensitive version of the test, it can deliver positive results more quickly, which allows doctors to diagnose a heart attack more quickly. The test is also able to show a patient’s risk of heart attacks and other heart events in the future. The test can be positive even if a person has no symptoms. The test is not approved in the United States at the time of writing, but research is still being conducted. It’s possible that it will be available at a future date. Canada, Europe, and several other countries already use this test as a cardiac biomarker. 

CK-MB – This is a form of the creatine kinase that can be found in cardiac muscle tissue. When the cells of the heart muscle are damaged, it rises. Now that troponin testing is an option, this test isn’t ordered as often.  

Additional tests that could be ordered are:  

Myoglobin – When there is an injury to either the heart or skeletal muscle, this protein is released into the blood. This is another test that is ordered less often.  

NT-proBNP or BNP – The body naturally releases this in response to heart failure. Although elevated BNP levels aren’t enough to diagnose a heart attack, it suggests that a person is at an increased risk for cardiac problems.  

There are additional screening tests that could be ordered to look at a patient’s electrolyte balance, organ health, blood glucose levels, and red and white blood cell count. Examples of these tests are:  

Comprehensive Metabolic Panel – This is a collection of 14 tests that can broadly screen the health of a patient’s liver, kidneys, blood proteins, blood glucose, and electrolyte and acid balance.  

Complete Blood Count: This test is used to screen for various disorders that can impact blood cells, like infection and anemia.