Stable vs Unstable Angina: an Acute Coronary Syndrome Overview

Acute coronary syndrome (ACS) is a term that describes when a blood clot forms inside the coronary arteries – there are two types: stable angina vs unstable angina. 

Angina technically means chest or heart pain, and both stable and unstable angina occur due to low oxygenation of the heart. 

Stable angina occurs when there is chest pain with activity (usually during physical exertion), but then subsides after taking medication or rest. Unstable angina is similar to stable angina, except that the chest pain worsens quickly and does not subside after medication or rest.

A key point to consider with angina is the vasoconstriction and vasodilation of blood vessels. So let’s dive into more detail.

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Vasoconstriction vs Vasodilation

When a person becomes physically active or is in a stressful situation, the sympathetic nervous system activates the fight and flight response. Once this happens, the blood vessels shrink and cause vasoconstriction. 

On the other hand, when a person is relaxed (like resting on a beach somewhere), vasodilation occurs. During vasodilation, rest and digestion are activated.

If a patient has coronary artery disease (CAD), which is caused by high cholesterol, there’s increased plaque formation within the lining of the blood vessels. This causes the passageway to constrict.

Why do Blood Vessels Constrict?

Blood vessels constrict when the body exerts effort during strenuous activities. During this time, the heart rate and blood pressure increase.

The blood vessels constrict to increase oxygen delivery to vital parts of the body such as; the heart, lungs, and brain. As a result, there’s increased blood pressure and heart rate because the body shunts all that oxygen into the blood vessels where it’s needed most.

What is Stable Angina?

Stable angina is also known as exercise-induced chest pain. When a patient exercises or physically exerts themself, the plaque or inflamed vessels become very narrow, which causes decreased oxygen delivery to the heart. When the patient stops the exercise or physical exertion, the chest pain also goes away, and breathing goes back to normal.

Stable Angina Symptoms

The symptoms of stable angina tend to be less severe and more long-lasting than unstable angina. The most common symptom is chest discomfort, pressure, or tightness that lasts for more than twenty minutes (and comes back again and again). Other stable angina symptoms can include:

• Pain in the shoulders, arms, neck, jaw, or back
• Shortness of breath (dyspnea)
• Crushing chest pain with coughing or wheezing
• Heart palpitations (a fast or irregular heartbeat)
• Fatigue, weakness, and/or lightheadedness

Stable Angina Pharmacology

Stable angina patients are commonly given Nitroglycerin. Also known as glyceryl trinitrate, it works by widening the arteries and relaxing the heart muscles. 

Other medications used to treat stable angina include:

Antiplatelet drugs: These help prevent blood clots from forming in the arteries, which can block blood flow to the heart muscle. Common examples include Aspirin and Plavix (Clopidogrel).

Beta blockers: These reduce the heart rate and blood pressure, making it easier for the patient’s heart to pump blood around the body with less effort. Beta blockers aren’t used as often for patients with stable angina because they can cause dizziness, fatigue, and cold hands and feet.

What is Unstable Angina?

Unstable angina occurs when a patient still experiences pain even after stopping a stressful physical activity. This is because the blood vessels have expanded, but the pain has remained consistent. 

This is most likely a case of unstable angina, which means a blood clot is blocking the coronary artery. Why does this happen?

When a patient exercises, the blood vessels shrink or become smaller to adequately and effectively deliver oxygenated blood to the vital organs in the body. As the body relaxes, the blood vessels expand, there will be tiny clots or platelets attached to the edges of the plaque, occluding the entire vessel.

So just a reminder, stable angina is relieved by rest, while unstable angina still causes chest pain even during rest.

Unstable Angina Symptoms

The most common symptom of unstable angina is chest pain or discomfort that occurs with physical activity or stress. Others include:

• Shortness of breath
• Fatigue
• Lightheadedness
• Sweating
• Nausea or vomiting
• Heart palpitations 
• Pain or discomfort spreading to shoulders, arms, neck, jaw, or back

Unstable Angina Pharmacology

Since unstable angina is not relieved by rest, the health care provider (HCP) will prescribe MONA – morphine, oxygen, nitrogen, and aspirin. 

MONA is a mnemonic to remember the best treatment practice in the care of unstable angina.  MONA has shown promising results in decreasing events that can lead to death.

But MONA is actually given as ANOM. How and why?

1. Aspirin – The first recipe that will be given to patients to thin out the congregated platelets. Aspirin breaks up the platelets to ensure they will not form around the plaque.
2. Nitrogen – Given for vasodilation or vaso-expansion.
3. Oxygen – Given after vasodilation.
4. Morphine – The last recipe to be given, especially if the top three recipes couldn’t take the chest pain away. Morphine is given last to determine if the patient is experiencing myocardial infarction. If the patient is still in pain after morphine administration, they can possibly experience a heart attack.

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