Stable vs Unstable Angina: Symptoms and When to Call 999
Call 999 now if chest pain or discomfort:
- Comes on at rest, or wakes you from sleep
- Lasts more than 15 minutes
- Is more severe, more frequent or easier to bring on than your usual angina
- Does not settle after two doses of your GTN spray, five minutes apart
- Comes with breathlessness, sweating, nausea, vomiting or a feeling of impending doom
- Spreads to the arm, jaw, neck, back or stomach
Do not drive yourself to hospital and do not wait to see whether it passes. If you are not allergic and have not been told otherwise, chew a 300mg aspirin while you wait for the ambulance. Angina that is new, worsening or occurring at rest is treated as a medical emergency because it can be the warning stage of a heart attack.
The difference between stable and unstable angina is not how much it hurts. It is whether the plaque in your coronary artery has stayed intact or started to break. Stable angina is predictable: it appears with exertion, it eases with rest, and the pattern stays roughly the same for months. Unstable angina is a change in that pattern, or new chest pain at rest, and it means a plaque has ruptured and a clot is forming. Stable angina is managed in clinic. Unstable angina is a 999 call.
That distinction is the whole point of this article, because it is the one that decides what you do in the next ten minutes.
Key takeaways
- Angina is a symptom, not a disease. It is chest discomfort caused by heart muscle not receiving enough oxygen rich blood.
- Stable angina is brought on by a predictable amount of exertion or stress and settles within minutes of resting or using a GTN spray.
- Unstable angina occurs at rest, lasts longer, or is a clear worsening of your usual pattern. It belongs to the acute coronary syndrome group alongside heart attacks.
- The mechanism differs. Stable angina involves a fixed narrowing. Unstable angina involves a ruptured or eroded plaque with a clot forming on it.
- Angina does not always present as chest pain. Breathlessness, jaw or arm ache, nausea and fatigue are common, especially in women, older people and people with diabetes.
- Vasospastic angina and microvascular angina are separate conditions and are often confused with unstable angina.
- Treatment has two separate goals: relieving symptoms, and reducing the risk of a future heart attack. Different drugs do each job.
- Chest pain that is new, worse or occurring at rest is an emergency. Call 999.
What is angina, exactly?
Your heart is a muscle, and like any muscle it needs a blood supply proportional to how hard it is working. That supply comes from the coronary arteries on the surface of the heart. Angina happens when demand outstrips supply, a mismatch doctors call myocardial ischaemia. The muscle is starved rather than dying, which is what separates angina from a heart attack, where a sustained blockage causes muscle to die.
The usual underlying cause is coronary artery disease, in which fatty deposits called atheroma build up in the artery wall over decades. A plaque narrowing an artery by around 70 percent or more starts to limit flow when demand rises, which is why symptoms first appear on a hill or a flight of stairs rather than sitting down.
The important framing is that angina is a message. It is your heart reporting that its blood supply has a limit, and that message is worth acting on whether it arrives predictably or suddenly.
What does angina actually feel like?
People expect crushing pain, and that expectation causes dangerous delays. Angina is more often described as heaviness, tightness, pressure or a band around the chest. Many people insist it is not pain at all, only discomfort, which is exactly why the word discomfort appears in every set of guidance.
It commonly spreads to the left arm, but it can equally affect both arms, the jaw, the neck, the upper back or the upper stomach. It may come with breathlessness, sweating, nausea or an overwhelming sense that something is wrong.
Some patterns make angina less likely, though none of them rule it out: pain that is sharp and stabbing, pain reproduced exactly by pressing on the chest wall, and pain that changes clearly with breathing or position.
Angina does not always look like the films
Women, people with diabetes and people over 75 are more likely to have atypical presentations, where breathlessness, unusual fatigue, indigestion like discomfort or nausea dominates and chest pain is mild or absent. Nerve damage from diabetes can blunt the warning entirely, producing so called silent ischaemia. Women are more likely to have their symptoms attributed to anxiety or reflux, and more likely to delay seeking help. If something feels wrong in your chest and you cannot explain it, get it assessed.
Stable and unstable angina side by side
| Feature | Stable angina | Unstable angina |
|---|---|---|
| What is happening in the artery | Fixed narrowing from a plaque with an intact fibrous cap | Plaque cap has ruptured or eroded and a clot is forming on it |
| When it happens | On exertion, cold, heavy meals or emotional stress | At rest, at night, or on far less exertion than before |
| Predictability | Reliable, the same trigger produces the same symptom | Unpredictable and changing |
| How long it lasts | Usually a few minutes | Longer, often more than 10 to 15 minutes |
| Response to rest or GTN | Settles promptly | Partial, slow or no relief |
| Classification | Chronic coronary syndrome | Acute coronary syndrome, alongside heart attack |
| What to do | See your GP, take prescribed treatment, attend follow up | Call 999 immediately |
The single most useful question is not how bad it is but has anything changed. Angina that used to appear at the top of the stairs and now appears halfway up, or that used to last two minutes and now lasts ten, has become unstable regardless of severity.
What is really happening in unstable angina
A plaque is not simply a lump of fat blocking a pipe. It is a lesion in the artery wall with a lipid rich core and a fibrous cap holding it in. Stability depends on that cap.
Plaques with thick fibrous caps tend to stay put, and they cause stable angina by narrowing the channel. Plaques with thin, inflamed caps are vulnerable. When such a cap tears or the surface erodes, the highly thrombogenic core is exposed to flowing blood. Platelets stick to it, a clot builds, and the artery narrows abruptly.
If that clot partially blocks the artery, you get unstable angina or a non ST elevation myocardial infarction, distinguished by whether blood tests show heart muscle damage. If it blocks the artery completely and persistently, muscle starts to die and you have a ST elevation myocardial infarction, the classic heart attack. These sit on one continuous spectrum, which is why unstable angina is treated with such urgency: the same process, a little further along, is a heart attack.
This also explains something counterintuitive. Many heart attacks arise from plaques that were not severely narrowing the artery beforehand. A modest but unstable plaque is more dangerous than a large stable one, so a normal exercise test last year does not guarantee safety today.
A myth worth correcting: plaque does not break off and float to your brain
A widely repeated explanation says that unstable plaque breaks away, travels through the bloodstream and causes a stroke by lodging elsewhere. It is a vivid picture and it is not how coronary events work.
When a coronary plaque ruptures, the damage is local. A clot forms at the rupture site and blocks that same artery downstream of it. Coronary arteries carry blood away from the heart into heart muscle, so material dislodged there cannot travel to the brain. The anatomy runs the wrong way.
Strokes caused by clots come from elsewhere: atherosclerosis in the carotid arteries in the neck, clots forming in the heart chambers during atrial fibrillation, or debris from a diseased aorta. Coronary disease and stroke share risk factors, which is why people with one often have the other, but they are not the same mechanism.
This matters practically. It means the aim of treatment is stabilising plaque and preventing clot formation in the coronary arteries themselves, which is precisely what statins and antiplatelet drugs are for. If you have seen claims that a food can replace those medicines, we took that argument apart in our piece on why garlic is not an alternative to a statin.
Two other kinds of angina that get confused with unstable angina
These are frequently mixed up in health articles, including the version this page replaces.
Vasospastic angina, also called Prinzmetal or variant angina, is caused by sudden spasm of a coronary artery rather than by a plaque. It characteristically occurs at rest, often in the early hours of the morning, and can affect arteries that look normal on an angiogram. It is treated primarily with calcium channel blockers and nitrates, and beta blockers can sometimes make it worse. Because it causes rest pain, it is easily mistaken for unstable angina, and it must be assessed urgently to tell them apart.
Microvascular angina involves the tiny vessels beyond the reach of an angiogram. Patients have genuine ischaemia with unobstructed major coronary arteries, a picture increasingly described as ANOCA or INOCA. It is more common in women, and it has historically been dismissed as non cardiac, leaving people without treatment for years. It is real, and it deserves proper assessment.
The practical message is unchanged. Chest pain at rest needs urgent assessment. Which of these it turns out to be is a job for a clinician with an ECG and a blood test, not for you at home.
How angina is diagnosed
Assessment usually follows a familiar sequence.
- History. Still the most powerful tool. The pattern, triggers, duration and what relieves it carry more diagnostic weight than any single test.
- ECG. A resting ECG can be entirely normal in stable angina, which does not exclude it. During an acute episode it can show ischaemic changes.
- Troponin blood test. Troponin is a protein released when heart muscle is damaged. It is what separates unstable angina, where troponin is not raised, from a heart attack, where it is.
- CT coronary angiography. In the UK this is the recommended first line investigation for stable chest pain thought to be cardiac. It images the arteries directly.
- Functional testing. Stress echocardiography or perfusion imaging shows whether an area of muscle is short of blood under load.
- Invasive coronary angiography. A catheter study, used where the picture is high risk or unclear, and allowing treatment during the same procedure.
Tell the hospital about your supplements
High dose biotin, found in many hair, skin and nail products, interferes with laboratory immunoassays and can make a troponin result read falsely low. In a chest pain assessment that is a genuine safety concern, so mention every supplement you take, by name. We explain the issue in more detail in our guide to whether collagen and other beauty supplements work.
How angina is treated
Treatment has two aims that are worth separating, because patients often assume one drug is doing both jobs.
| Aim | Typical treatments | What it does |
|---|---|---|
| Relieve symptoms now | Glyceryl trinitrate spray or tablets | Widens vessels within minutes during an attack |
| Prevent attacks | Beta blockers, calcium channel blockers, long acting nitrates, ivabradine, ranolazine | Reduces the heart's oxygen demand or improves supply |
| Reduce future heart attack risk | Antiplatelet therapy such as aspirin or clopidogrel, statins, blood pressure treatment | Stabilises plaque and makes clot formation less likely |
| Restore blood flow | Angioplasty with stent, or coronary artery bypass surgery | Physically reopens or bypasses a narrowed artery |
The distinction that surprises people is that the drugs relieving symptoms and the drugs extending life are largely different. A GTN spray makes you feel better and changes nothing about your long term risk. A statin does almost nothing for today's symptoms while meaningfully reducing the chance of a future heart attack. Both are worth taking, for different reasons, which is why stopping the statin because you feel fine is a mistake.
How to use a GTN spray properly
If you have been prescribed one, the standard approach is to stop and rest, use one dose under the tongue, and wait five minutes. If the discomfort remains, take a second dose and wait five more minutes. If it has not settled five minutes after the second dose, call 999. Sit down when using it, since it commonly causes a headache, flushing or light headedness, and never take it alongside erectile dysfunction medicines such as sildenafil, which can cause a dangerous drop in blood pressure. Always confirm the routine your own clinician has given you.
Living with stable angina
A diagnosis of stable angina is not a sentence to a smaller life. Many people continue working, exercising and travelling, and cardiac rehabilitation programmes exist precisely to rebuild confidence in activity. Regular exercise within your limits is beneficial rather than risky, though it should be started on medical advice.
The things that change outcomes are consistent: stopping smoking, taking prescribed medicines reliably, controlling blood pressure and blood sugar, and knowing your own pattern well enough to notice when it changes. Understanding what actually brings on an angina attack makes daily life considerably easier to plan.
One small thing worth knowing, since people find it alarming and nobody warns them: noticeable hair shedding two to three months after a cardiac event, hospital admission or surgery is common. It is called telogen effluvium, it is a delayed response to physical stress rather than a sign of anything new going wrong, and it usually recovers on its own. Our guide to the main causes of hair loss covers the pattern. Raise it with your GP rather than changing any heart medication over it.
Frequently asked questions
What is the main difference between stable and unstable angina?
Predictability and mechanism. Stable angina appears with a consistent amount of exertion and settles with rest, caused by a fixed narrowing. Unstable angina occurs at rest or represents a clear worsening of your usual pattern, and is caused by a ruptured plaque with a clot forming on it. Unstable angina is an emergency.
Can unstable angina turn into a heart attack?
Yes. They are part of the same acute coronary syndrome spectrum. Unstable angina means the clot is partially blocking the artery without yet causing detectable muscle damage. If the blockage becomes complete, muscle begins to die and it becomes a heart attack.
How long does angina last?
Stable angina usually lasts a few minutes and eases with rest or GTN. Discomfort lasting more than 15 minutes, or not relieved by two doses of GTN five minutes apart, should be treated as an emergency and you should call 999.
Can you have angina with normal coronary arteries?
Yes. Vasospastic angina involves temporary spasm of an artery that may look normal, and microvascular angina affects vessels too small to see on an angiogram. Both cause genuine ischaemia and both deserve proper assessment rather than dismissal.
Is angina the same as a heart attack?
No. In angina the heart muscle is short of oxygen but survives. In a heart attack the blockage is sustained and muscle dies, which is detected by a rise in troponin in the blood.
Does angina show up on a normal ECG?
Not necessarily. A resting ECG is often completely normal in stable angina, so a normal trace does not rule it out. This is why history, CT coronary angiography and functional testing matter.
Can stress alone cause angina?
Emotional stress raises heart rate and blood pressure, increasing the heart's oxygen demand, and can bring on an attack in someone with existing coronary narrowing. It is a trigger acting on underlying disease rather than a cause of the disease itself.
Should I take aspirin if I think I am having a heart attack?
Current UK advice is to call 999 first, then chew a 300mg aspirin while waiting, provided you are not allergic to it and have not been told to avoid it. Chewing gets it into the bloodstream faster than swallowing whole.
The bottom line
Stable angina is a warning you can plan around. Unstable angina is a warning you act on immediately. The line between them is not the intensity of the discomfort but whether the pattern has changed, and any chest discomfort that is new, worse, longer lasting or occurring at rest should be treated as an emergency.
Watermans is a UK hair care company, not a medical provider, and there is deliberately nothing for sale on this page. If any of this sounds like you, the right next step is a GP appointment or, if symptoms are happening now, a 999 call.
