Stable vs. Unstable Angina: Differences and Similarities

Medically reviewed by Anthony Pearson, MD, FACC

Angina is a type of chest pain that results from poor blood flow to the heart muscle, typically from blocked coronary arteries. It is a condition marked by localized squeezing pressure, tightness, or a painful "strangling sensation" in the chest, arms, or jaw caused by the heart not getting enough oxygen due to insufficient blood flow.

Stable angina follows a pattern and occurs during physical exertion, while unstable angina doesn't follow a pattern and can occur without physical exertion. Unstable angina is more dangerous and may be a warning that a person is at imminent risk of a heart attack.

Read on to learn what you need to know about the difference between stable and unstable angina, including common versus emergency symptoms, why unstable angina is more intense and serious than stable angina, tests doctors use to confirm unstable angina, treatment options, and more.

Stable vs. Unstable Angina: Main Differences

Below is a side-by-side comparison list that shows similarities and differences between stable and unstable angina.

Stable Angina

• Chest pain near the heart

• Caused by the heart not getting enough blood flow and oxygen

• Symptom of heart disease

• Less serious, more common
  

• Not always an emergency

• Predictable

• "Stable" consistent pattern

• Triggered by exertion, exercise, strong emotions, anxiety, eating a big meal, etc.

• Rest, relaxation, and calmness typically relieve symptoms

• Usually lasts one to five minutes; rarely lasts longer than 15 minutes

• Not classified as acute coronary syndrome (ACS)

Unstable Angina

• Chest pain near the heart

• Caused by the heart not getting enough blood flow and oxygen

• Symptom of heart disease

• More serious, deadlier

• Always an emergency

• Unpredictable

• "Unstable" nonexistent pattern

• Not triggered by any predictable factors (often occurs out of the blue while reclining or sleeping)

• Rest and relaxation do not quickly resolve symptoms

• Often lasts longer than 15 minutes; can last 30 minutes or more

• Classified as acute coronary syndrome (ACS)

Acute coronary syndrome (ACS) is characterized by an abrupt, life-threatening reduction in the heart's blood supply. Unstable angina is a form of ACS; stable angina is not.

Although stable angina isn't considered an ACS, it can become unstable angina if you don't take steps to slow it.

Common Symptoms

Angina feels like a heavy pressure and tightness in the chest, but the pain or squeezing sensation can also be felt in other locations near the heart, such as the arms, shoulders, neck, or jaw.

Stable and unstable angina cause defects in the heart's functioning and its ability to sufficiently supply the heart with blood. But their seriousness and potential deadliness are different: Unstable angina is much more dangerous and should always be treated with life-or-death urgency as a medical emergency.

Stable and unstable angina symptoms may seem similar at the first sign of chest pain. However, unstable angina is unpredictable and doesn't quickly resolve with rest, relaxation, or the calming of strong emotions. It also causes more severe, longer-lasting symptoms requiring immediate medical attention at a nearby hospital or by calling 911.

Potential Angina Complications

Angina symptoms are caused by myocardial ischemia, a medical term that means “restricted blood supply to the heart.” When the heart doesn’t get enough blood, it can cause complications such as abnormal heart rhythms (cardiac arrhythmias), heart failure, heart tissue death (myocardial necrosis), or heart attacks.

Emergency Symptoms

You should call 911 or go to the emergency room (ER) if your stable angina symptoms seem different than usual or are accompanied by any of the following:

• Previously predictable angina symptoms occur unpredictably

• Symptoms last five minutes or longer

• Chest pain radiates to the arm, upper back, neck, or jaw

• Skin breaks out in a cold sweat

• Shortness of breath

• Dizziness

• Nausea

• Vomiting
  

Causes and Risk Factors

The most common underlying cause of stable and unstable angina is atherosclerosis, a condition marked by plaque buildup inside the heart’s arteries, which is a sign of coronary artery disease (CAD). Other causes include coronary microvascular dysfunction and coronary artery spasm.

Risk factors for both stable and unstable angina include:

• Age (Getting older increases risk)

• Underlying medical conditions (high blood pressure, cardiomyopathy, diabetes, etc.)

• Hereditary factors (e.g., having a family history of heart disease)

• Smoking cigarettes

• Being overweight

• Drug use (amphetamines can cause angina-inducing heart damage)

• Insufficient sleep or poor sleep quality

• Unhealthy eating habits

• Lack of physical activity
  

• Stress

• High levels of low-density lipoprotein (or "bad") cholesterol
  

How Is Stable vs. Unstable Angina Treated?

Vasodilators are medications that dilate the arteries and veins; they are first-line treatments for both stable and unstable angina. Common vasodilators for treating angina are nitroglycerin and a nitrate medication called Imdur (isosorbide mononitrate).Another relatively new anti-angina drug is Ranexa (ranolazine).

People experiencing chronic angina are usually prescribed two or more of the following types of drugs:

• Nitrates

• Beta-blockers

• Calcium channel blockers

• Late sodium current blockers (e.g., Ranexa)
  

Vasodilation vs. Vasoconstriction

Angina is caused by a narrowing of the arteries, which constricts blood flow (also known as vasoconstriction) to the heart. Nitrates that treat angina improve blood flow by widening coronary arteries (this is also called vasodilation).

Because unstable angina is more serious than stable angina, it requires more aggressive treatment. Most people with stable angina don't need surgery. The gold standard for most people with stable angina is non-invasive medical treatment such as medications and heart-healthy lifestyle changes.

People with unstable angina usually require an invasive surgical procedure such as angioplasty with stenting to unblock clogged arteries. In addition to making lifestyle changes and having a surgical procedure, unstable angina treatment often includes different prescription drugs, including anti-ischemic agents, anticoagulants, and antiplatelets.

Physical Activity and Rehabilitation With Angina

Physical activity is key to making heart-healthy lifestyle choices that reduce angina risk. That said, because strenuous exercise can trigger angina symptoms, it's important to work closely with a trained professional when using physical activity as part of rehabilitation with angina.

Long-Term Management, Follow-Up, and Living Well

Long-term management of stable and unstable angina involves living well by making heart-healthy lifestyle choices and scheduling regular follow-up visits with a healthcare provider for checkups.

Because stable angina symptoms tend to be predictable, the American Heart Association has a downloadable "Cardiac Rehabilitation Angina Log" for tracking the date of any angina attacks, what triggered it, its intensity rating (1–4), how long it lasted, and what you did to alleviate its symptoms. You should share this log with your healthcare provider during follow-up visits.

Long-term management of stable and unstable angina aims to prevent the progression of blockages and to avoid severe consequences associated with coronary artery disease, such as deadly heart attacks.

Summary

Angina means "chest pain." Stable and unstable angina are both caused by plaque buildup, which blocks the heart's blood flow. They share similar symptoms: constricted feelings of heavy pressure, tightness, or a squeezing "strangling sensation" in the chest area near the heart.

Unstable angina is unpredictable and more serious than stable angina. Strenuous exercise and strong emotions can trigger stable angina. But unstable angina doesn't have clear triggers; it can happen anytime, even when someone's relaxed or sleeping.

Sitting down or resting usually relieves stable angina symptoms in less than five minutes. However, taking it easy or relaxing doesn't relieve unstable angina symptoms, which generally last longer than 15 minutes and can lead to a heart attack or death.

Unstable angina is a medical emergency that almost always requires surgery to remove the heart's blockage. Stable angina doesn't necessarily require surgery and is primarily treated with medicine and heart-healthy lifestyle changes.

Read the original article on Verywell Health.