Unstable Angina vs. Stable Angina?
Angina is the name given to the symptoms (usually chest pain or chest discomfort) produced when the heart muscle is in a state of ischemia-that is, when the heart muscle is not getting enough blood supply. In unstable angina, ischemia occurs unpredictably and suddenly, usually because a blood clot has suddenly formed within a coronary artery, temporarily limiting blood flow to the heart muscle.
Key Points
Unstable angina is often exacerbated by the formation of temporary blood clots within the coronary arteries. If the blood clots persist, a heart attack can occur. It’s not surprising, then, that unstable angina often occurs before a heart attack and should be treated aggressively.
Unstable angina is a pattern of angina that occurs randomly or unpredictably and is unrelated to any obvious trigger (such as physical exertion or emotional stress). Unstable angina is a form of acute coronary syndrome (ACS), and like all ACS, unstable angina should be considered a medical emergency.
What is Unstable Angina?
Angina is considered to be “unstable” when it no longer follows the predictable patterns typical of “stable angina.”
Unstable angina is called “unstable” for two reasons.
1. in contrast to stable angina, symptoms occur in a more random and unpredictable fashion. While in stable angina, symptoms 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 can even wake people from a restful sleep. Furthermore, in unstable angina, the symptoms often persist for more than just a few minutes, and nitroglycerin often fails to relieve the pain. So, unstable angina is “unstable” because symptoms may occur more frequently than usual, without any discernible trigger, and may persist for a long time.
2. more importantly, 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 are producing partial blockage of the artery. The partial blockage may take 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 is very high in unstable angina. Obviously, such a condition is quite “unstable,” and for this reason, it is a medical emergency.
When Should You Be Concerned That You Have Unstable Angina?
Anybody with a history of coronary artery disease should suspect unstable angina if their angina begins to occur at lower levels of physical exertion than normal, if it occurs at rest, if it persists longer than usual, if it is more difficult to relieve with nitroglycerin, or especially if it wakes them up at night.
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, unfortunately, they often don’t recognise the symptoms as being angina. The classic symptoms of angina include chest pressure or pain, sometimes squeezing or “heavy” in character, often radiating to the jaw or left arm. Unfortunately, many patients with angina do not have classic symptoms. Their discomfort may be very mild and may be localised to the back, abdomen, shoulders, or arms. Nausea, breathlessness, or merely a feeling of heartburn may be the only symptoms. 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.
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.
How Is Unstable Angina Diagnosed?
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 20 minutes at a time.
- Angina that has recently developed and severely 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 ECG and blood tests for cardiac enzyme testing.
If the portion of the ECG known as “ST segments” is 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. Because these two conditions are so similar, their treatment is identical.
What Is the Treatment for Unstable Angina (and NSTEMI)?
If you have either unstable angina or NSTEMI, you will be treated with one of two general approaches: a) treat aggressively with drugs to stabilise the condition, then evaluate non-invasively; or b) treat aggressively with drugs to stabilise the condition, and schedule early-invasive intervention (generally, angioplasty and stenting).
What is Stable Angina?
Stable Angina is the name given to the symptoms (usually chest pain or chest discomfort) produced when the heart muscle is in a state of ischemia-that is, when the heart muscle is not getting enough blood supply. Stable angina occurs when there is a partial blockage in a coronary artery that limits the maximum blood flow to the heart muscle.
Patients with stable angina usually have no symptoms during rest with mild activity since blood flow to the heart muscle is adequate under these conditions. However, during periods of exercise or other
conditions of stress in which the heart muscle requires more oxygen, the partial blockage prevents an adequate increase in blood flow. This lack of sufficient blood flow under these circumstances produces ischemia, thus leading to angina.
This condition is called “stable” angina because the symptoms occur in a predictable fashion—that is, they occur only under conditions such as exercise or other stresses that require the heart to work harder.
In contrast, in unstable angina, symptoms occur unpredictably, most often at rest.
