When the oxygen supply to the heart is cut off or greatly reduced, we get into a situation called Acute Coronary Syndrome (ACS). Within this syndrome we have both myocardial infarction and unstable angina. At this point, you may be asking “what is the difference between unstable and stable angina?” 

Stable vs unstable angina in acute coronary syndrome

Angina can be characterized based on how dangerous it is for the patient. Stable angina is typically brought on by exercise or stress and is relieved by rest and/or nitroglycerin. Unstable angina, however, requires more intense intervention and is considered a medical emergency. For the record, there are several types of angina, but for now let’s just focus on stable vs. unstable. Blog post coming soon about all the types of angina! 

Acute myocardial infarction (AMI)

AMI occurs when blood flow to the heart is blocked to the point of causing ischemia and tissue damage. This is what most people call a “heart attack.” The blockage can be caused by a blood clot or buildup of plaque in the arteries (this condition of plaque buildup is called atherosclerosis). This area of plaque buildup can break open, or break free, causing a clot to form in the coronary arteries. The clot blocks blood flow and oxygen to that area of the heart and, if left untreated, that muscle tissue dies. When there is a lack of oxygen, we refer to this as ischemia…ischemia is typically the cause of pain in myocardial infarction and unstable angina. After all, an oxygen-starved and dying heart muscle hurts! 

Symptoms of acute coronary syndrome

  • The hallmark sign is chest pain, pressure, tightness or a feeling of fullness
  • Pain could include the jaw, neck, stomach, back or arms (sometimes just one arm)
  • Feeling shortness of breath
  • Nausea or indigestion; some patients may think they just have an upset stomach
  • Dizziness, feeling lightheaded
  • Sweating, AKA diaphoresis
  • Fatigue

Not everyone experiences chest pain!

I know, I know…the movies always show a guy clutching his chest, grimacing and falling to the ground. But, not everyone who has an MI will experience chest pain. For example, patients with diabetes will often not experience chest pain due to the damage that the disease causes the nerves (a condition called neuropathy). Also, studies show that women can experience MI differently than men and may be more likely to report symptoms of shortness of breath, back pain, jaw pain and nausea/vomiting. And what about heart transplant patients? This study looked at 22 patients almost four years after their transplants who had episodes of AMI. Of those 22, only two had chest  pain, while most had shortness of breath and weakness as their main symptoms. The point is, an MI can occur WITHOUT crushing chest pain…when this occurs, it’s often referred to as a “silent MI.” 

How is ACS treated?

Looking at the ACLS guidelines determined by the American Heart Association, ACS in the hospital is treated in a systematic way. 

  • After getting a set of vitals, oxygen is recommended for O2 saturations < 94% or in cases where the patient is experiencing shortness of breath. 
  • Someone will need to get an IV in the patient, and the patient needs a 12-lead ECG right away. An x-ray may also be ordered, but when it is conducted is likely determined by the severity of the patient’s symptoms. 
  • Labs will be collected to examine cardiac enzymes, coagulation status, lipid profile and a metabolic panel
    • For cardiac markers myoglobin is released first, followed by troponins and CK-MB. Troponin I has the most specificity for cardiac muscle necrosis, followed by CK-MB, then myoglobin. So even though myoglobin rises first, it’s not all that specific for an MI. The team will need to take the patient’s whole story into account when looking at these lab results. (I made a handy graphic for you below for those of you who are more visual learners.)
  • The acronym MONA is helpful to remember the key components…but be aware that MONA does not indicate the ORDER in which these things are done! 
    • Oxygen if  needed (most likely will be!)
    • Aspirin if not already given
    • Nitroglycerin sublingual or translingual spray. It’s important to note that you’ll want to look at the ECG before giving the nitroglycerin…this is because it’s not recommended in right-ventricular infarct. In right heart failure, the heart needs MORE preload, not less. I’m doing a whole, extensive post on nitroglycerin…but for now just know that it reduces preload. Your patient with a right ventricular infarct needs that preload because the right side of their heart is not working well right now!
    • Narcotic such as morphine, dilaudid or fentanyl if the pain does not resolve with nitroglycerin administration. If nitro relieves the pain, this could mean the arteries have opened and the heart is getting oxygen…if the nitro doesn’t help, it’s generally a sign that things are very serious. The M in MONA  stands for morphine as it’s generally considered the drug of choice.
    • The acronym is more like ONAM or OANM…depending on when your facility’s protocol dictates giving the nitro vs the aspirin. 
  • Based off the ECG, the MD will determine if the patient is having a STEMI or NSTEMI
    • STEMI (ST-elevation MI)
      • STEMI treatment involves re-perfusion therapy…get that patient to the cath lab stat!
      • Based on the patient’s history and full clinical picture they could also receive ACEi or ARB, statins, beta blockers, an anti-platelet agent and an anticoagulant.
    • NSTEMI (Non ST-elevation MI) or unstable angina
      • These patients may receive nitroglycerin to open those coronary arteries, an ARB, an anti-platelet agent and an anticoagulant such as heparin.
      • High-risk patients may continue to receive aspirin and also get a statin added to the mix.
Note that various sources give Troponin I an onset range from 3 to 8 hour; the general consensus is represented here.

What puts a patient at risk for ACS?

There are a number of risk factors for acute coronary syndrome; we’ll break them down into unmodifiable vs modifiable. 

  • Unmodifiable risk factors for ACS
    • Age, the older we get, the greater risk we have. Since age is not something we can change, this is considered an unmodifiable risk factor.
    • Family history of heart disease, stroke or ACS
    • Type 1 diabetes 
  • Modifiable risk factors  for ACS
    • Smoking cigarettes
    • Hypercholesteremia
    • Uncontrolled hypertension or a history of  preeclampsia
    • Unhealthy diet 
    • Lack of physical activity (this was me in nursing school!)
    • Being obese or overweight
    • Type 2 diabetes

Preventing acute coronary syndrome

The best ways to prevent acute coronary syndrome is to address those modifiable risk factors. Some patients will also take medications to reduce their risk….these can include aspirin, anti-platelet agents, statins, ACEi, BB, CCB, ranalazine and/or nitroglycerin

Patients with chronic coronary artery disease may need a stent to keep those arteries open or cardiac bypass surgery, which you’ll often hear referred to as a CABG (pronounced “cabbage”). When we talk about the CABG, we usually specify how many arteries were bypassed. So, a quadruple bypass means four arteries were bypassed, whereas a quintuple bypass means five!

As for the modifiable risk factors, provide the patient/family with education on all the things they can do to mitigate them. They may need smoking cessation information and resources, support losing weight, a physical therapy consult if they’re so weakened they can’t exercise regularly, a dietician consult to maximize their nutrition, diabetes education if they have type 2 diabetes related to diet and weight, and so on.

For more, check out these great companion posts about all the different types of angina and the oh-so-fascinating medication nitroglycerin. See you soon!

Get this on audio in episode 60 of the Straight A Nursing podcast


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ACLS Training Center. (2019). Acute Coronary Syndromes Algorithm. Retrieved July 24, 2019, from https://www.acls.net/acute-coronary-syndromes-algorithm.htm

Gao, S. Z., Schroeder, J. S., Hunt, S. A., Billingham, M. E., Valantine, H. A., & Stinson, E. B. (1989). Acute myocardial infarction in cardiac transplant recipients. The American Journal of Cardiology64(18), 1093–1097. https://doi.org/10.1016/0002-9149(89)90858-8

heart.org. (n.d.). Acute Coronary Syndrome. Retrieved July 24, 2019, from www.heart.org website: https://www.heart.org/en/health-topics/heart-attack/about-heart-attacks/acute-coronary-syndrome

Mayo Clinic. (n.d.-a). Coronary artery disease – Diagnosis and treatment – Mayo Clinic. Retrieved July 24, 2019, from https://www.mayoclinic.org/diseases-conditions/coronary-artery-disease/diagnosis-treatment/drc-20350619

Mayo Clinic. (n.d.-b). Heart attack – Symptoms and causes. Retrieved July 24, 2019, from Mayo Clinic website: https://www.mayoclinic.org/diseases-conditions/heart-attack/symptoms-causes/syc-20373106