An Overview of Unstable Angina

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Unstable angina causes random or unpredictable chest pain, as a result of partial blockage of an artery that supplies the heart. In contrast to stable angina, the pain or discomfort of unstable angina often occurs while resting, lasts longer, is not eased with medication, and is unrelated to any obvious trigger, such as physical exertion or emotional stress.

Diagnosis of unstable angina, a form of acute coronary syndrome (ACS), is often done in the emergency room and requires a combination of patient symptoms, an electrocardiogram (ECG), and cardiac enzymes (a blood test).

Treatment entails taking medications to ease the chest pain and associated ischemia (when the heart is not obtaining adequate blood flow). Medications to stop blood clot formation within the affected artery are also given. In some cases, an invasive intervention called angioplasty with stenting (where the blocked artery is opened) is required.

unstable angina
Verywell / Gary Ferster


The classic symptoms of angina include chest pressure or pain, sometimes squeezing or “heavy” in character, often radiating to the jaw or left arm.

Keep in mind though, many patients with angina do not have classic symptoms. Their discomfort may be very mild and may be localized to the back, abdomen, shoulders, or either or both arms. Nausea, breathlessness, or merely a feeling of heartburn may be the only symptom.

What this means, essentially, is that anyone middle-aged or older, especially anyone with one or more risk factors for coronary artery disease, should be alert to symptoms that might represent angina.

In addition, people without any history of coronary artery disease can also develop unstable angina. Unfortunately, these people seem to be at higher risk of a heart attack because they often don’t recognize the symptoms as being angina.

In the end, anybody with a history of coronary artery disease should suspect unstable angina if their angina occurs in the following situations:

  • At lower levels of physical exertion than normal
  • At rest
  • Persists longer than usual, or especially if it wakes them up at night
  • Is not eased by nitroglycerin (a medication that relaxes and widens coronary arteries)

Important Message

If you think there is any possibility you might have unstable angina, you need to go to your doctor, or to an emergency room, immediately.


Unstable angina is "unstable" because, as with all forms of ACS, it is most often caused by the actual rupture of a plaque in a coronary artery.

In unstable angina, the ruptured plaque, and the blood clot that is almost always associated with the rupture, creates a partial blockage of the artery. This partial blockage may create a "stuttering" pattern (as the blood clot grows and shrinks), producing angina that comes and goes in an unpredictable fashion.

If the clot should cause complete obstruction of the artery (which happens commonly), the heart muscle supplied by that affected artery is in grave danger of sustaining irreversible damage. In other words, the imminent risk of a complete myocardial infarction (heart attack) is very high in unstable angina. Obviously, such a condition is quite "unstable," and for this reason is a medical emergency.

No Apparent Trigger/Unpredictable Pattern

Looking deeper into its meaning, unstable angina is considered "unstable" because it no longer follows the predictable patterns typical of "​stable angina."

First, in contrast to stable angina, symptoms of unstable angina occur in a more random and unpredictable fashion. More specifically, while symptoms of stable angina are typically brought on by exertion, fatigue, anger, or some other form of stress, in unstable angina, symptoms can (and often do) occur without any apparent trigger.

In fact, unstable angina often occurs at rest, and may even wake a person from a restful sleep. Furthermore, in unstable angina, the symptoms often persist for more than just a few minutes.


Unstable angina is "unstable" because symptoms may occur more frequently than usual, without any discernible trigger, and may persist for a long time.

Important Point

If you think there is any possibility you might have unstable angina, you need to go to your doctor, or to an emergency room, immediately.


Symptoms are critically important in making the diagnosis of unstable angina, or indeed, any form of ACS.

In particular, if you have one or more of the following three symptoms, your doctor should take that as a strong clue that one type or another of ACS is occurring:

  • Angina at rest, especially if it lasts more than 10 minutes at a time
  • New onset angina that markedly limits your ability to engage in physical activity
  • An increase in prior stable angina, with episodes that are more frequent, longer lasting, or occur with less exertion than previously

Once your doctor suspects ACS, he should immediately get an electrocardiogram (ECG) and blood tests for cardiac enzyme testing.

ECG and Cardiac Enzymes

If the portion of the ECG known as "ST segments" are elevated (which indicates that the artery is completely blocked), and the cardiac enzymes are increased (which indicates cardiac cell damage), a "large" myocardial infarction (MI) is diagnosed (also called an "ST-segment elevation MI," or STEMI).

If the ST segments are not elevated (indicating that the artery is not completely blocked), but the cardiac enzymes are increased (indicating that cell damage is present), a "smaller" MI is diagnosed (also called a "non-ST segment MI," or NSTEMI).

If the ST segments are not elevated and the enzymes are normal (meaning the artery is not completely blocked and no cell damage is present), unstable angina is diagnosed.

Notably, unstable angina and NSTEMI are similar conditions. In each condition, a plaque rupture has occurred in a coronary artery, but the artery is not completely blocked so at least some blood flow remains.

In both of these conditions, the symptoms of unstable angina are present. The only difference is that in an NSTEMI enough heart cell damage has occurred to produce an increase in cardiac enzymes.

Important Note

Because unstable angina and NSTEMI are so similar, their treatment is identical.


If you have either unstable angina or NSTEMI, you will be treated with one of two general approaches:

  • Treated aggressively with medications to stabilize the condition, then evaluated non-invasively
  • Treated aggressively with medications to stabilize the condition, and receive an early invasive intervention (generally, angioplasty and stenting).​


There are three main types of medications used to treat unstable angina— anti-ischemic, antiplatelet, and anticoagulant medications.

Anti-Ischemic Therapy

Sublingual nitroglycerin, an anti-ischemic medication, is often given to alleviate any ischemic chest pain.

For persistent pain, intravenous (through the vein) nitroglycerin may be given, assuming no contraindications (for example, low blood pressure). Morphine may also be given for persistent pain.

A beta-blocker, another anti-ischemic medication, will also be given, assuming no contraindications, such as signs of heart failure.

Side Note

A beta-blocker can lower a person's blood pressure and heart rate, both of which, when high, increase the heart's oxygen consumption requirements.

Finally, a cholesterol-lowering medication called a statin, like Lipitor (atorvastatin) or Crestor (rosuvastatin), will be given.

Side Note

Statins have been found to decrease the rate of heart attacks, death from coronary heart disease, need for myocardial revascularization, and stroke.

Antiplatelet Therapy

Antiplatelet medications, which prevent platelet clumping, will be given. This includes both aspirin and a platelet P2Y12 receptor blocker—either Plavix (clopidogrel) or Brilinita (ticagrelor).

Anticoagulant therapy (which thins the blood), like unfractionated heparin (UFH) or Lovenox (enoxaparin), will also be given.

Possible Invasive Intervention

Once stabilized with medication, a cardiologist will decide whether a patient needs an invasive intervention, usually angioplasty with stenting—a procedure (also called a percutaneous coronary intervention, or PCI) in which the partially blocked artery is first unblocked using a balloon catheter and then permanently propped open with a stent.

Determining whether to proceed with angioplasty and stenting is a very important decision. One tool many cardiologists use to help guide this decision is called the TIMI (thrombolysis in myocardial infarction) score.

The TIMI Score is based on the following risk factors:

  • Age 65 years or older
  • Presence of at least three risk factors for coronary heart disease (hypertension, diabetes, dyslipidemia, smoking, or a positive family history of an early myocardial infarction)
  • Prior coronary artery blockage of 50 percent or more
  • At least two episodes of angina in the last 24 hours
  • Elevated cardiac enzymes
  • Use of aspirin in the last seven days

TIMI Scoring

A low TIMI score (0 to 1) indicates a 4.7 percent chance of having an adverse heart-related outcome (for instance, death, heart attack, or severe ischemia requiring revascularization).

A high TIMI score (6 to 7) indicates a 40.9 percent chance of having an adverse heart-related outcome—and thus, nearly always warrants an early intervention like PCI.

A Word From Verywell

If you are experiencing new or worsening chest pain or chest pain that will not go away with rest or medication, you need to go to the emergency room right away. Even if your pain turns out to not be heart-related, that is OK. It's much better to be cautious and safe than to risk your life.

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Article Sources

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