Angina pectoris is chest pain or pressure caused by reduced blood flow to the heart muscle. The most common cause is coronary artery disease, where fatty deposits narrow the arteries that supply your heart. But several other conditions can trigger it too, from artery spasms to problems with the heart’s smallest blood vessels.
How Coronary Artery Disease Causes Angina
The process starts with damage to the inner lining of a coronary artery. White blood cells migrate into the artery wall, absorb cholesterol, and die, leaving behind fatty deposits. Smooth muscle cells move in and build a tough, fibrous cap over this growing mass of fat and debris. Over years, the deposit develops a lipid-rich core that can progressively narrow the artery.
When the artery is significantly narrowed, it can still deliver enough blood to your heart at rest. But during exercise, emotional stress, or other situations that make the heart work harder, the narrowed artery can’t keep up with demand. Your heart muscle needs more oxygen than it’s getting, and the result is the squeezing, pressure-like chest pain that defines angina.
This supply-demand mismatch is the core mechanism behind most angina. The heart isn’t being damaged permanently during an episode. It’s signaling that it temporarily isn’t getting enough blood. That’s why the pain typically fades within a few minutes of resting or slowing down.
Stable Angina: The Predictable Pattern
Stable angina is the most common type. It follows a consistent pattern for at least two months: pain shows up during physical activity or stress, lasts a few minutes, and goes away with rest. If you have it, you can generally predict when it will happen. Walking uphill triggers it, for example, or shoveling snow, or a stressful argument. The underlying blockage isn’t changing rapidly, so the threshold that triggers pain stays roughly the same from week to week.
Unstable Angina: A Warning Sign
Unstable angina breaks the pattern. Pain may come on without exertion, last longer than usual, or feel more intense. Rest doesn’t always relieve it. This shift typically happens when a plaque in a coronary artery cracks or erodes, triggering a blood clot that further restricts flow. Even plaques that weren’t causing significant narrowing can rupture and suddenly create a dangerous blockage.
Unstable angina sits on a spectrum with heart attacks. The 2025 guidelines from the American College of Cardiology and American Heart Association classify it alongside two types of heart attack as part of “acute coronary syndromes,” a group of related conditions that all stem from disrupted plaques and clot formation. The key difference is that unstable angina doesn’t cause permanent heart muscle death. But it can progress to a heart attack quickly, which is why any change in your angina pattern, pain lasting longer, happening more often, or occurring at rest, needs immediate medical attention.
Coronary Artery Spasm (Prinzmetal Angina)
Not all angina comes from plaque buildup. In Prinzmetal angina, the coronary arteries temporarily spasm, clamping down and choking off blood flow to the heart. This usually happens between midnight and 8 a.m. while you’re resting or asleep, which is the opposite of typical angina triggered by exertion.
Known triggers include smoking, cocaine and marijuana use, exposure to cold, emotional stress, and certain medications that constrict blood vessels (some migraine treatments and decongestants containing ephedrine). The arteries themselves may look completely normal on imaging between episodes, with no significant plaque. Pain can be severe and is often accompanied by changes on an EKG that mimic a heart attack.
Microvascular Angina
Sometimes angina occurs even though the major coronary arteries are wide open. The problem lies deeper, in the tiny blood vessels that branch off into the heart muscle itself. This is called coronary microvascular dysfunction, and it’s far more common than doctors once thought.
The small vessels may fail to dilate properly when the heart needs more blood, or they may spasm, or their walls may thicken and increase resistance to flow. The result is the same: the heart muscle doesn’t get enough oxygen, and you feel chest pain. But because standard tests like coronary angiography look at the large arteries, this type of angina often goes undiagnosed for years.
Microvascular angina is significantly more common in women. Research from the Women’s Ischemia Syndrome Evaluation study found that microvascular dysfunction is highly prevalent among women who have chest pain but no visible blockages in their major arteries. Several biological factors contribute to this sex difference, including the effects of sex hormones on blood vessel function, differences in how the autonomic nervous system regulates small vessels, and varying susceptibility to oxidative stress. Women are also more likely to develop ischemia from mental stress through a mechanism involving peripheral microvascular dysfunction rather than the large increases in heart rate and blood pressure more typical in men.
Structural Heart Conditions
Several heart problems cause angina without any coronary artery disease at all. In aortic stenosis, the valve controlling blood flow out of the heart narrows, forcing the heart to pump harder. The thickened muscle that results needs more oxygen, but the increased pressure makes it harder for blood to flow into the coronary arteries during each heartbeat.
Hypertrophic cardiomyopathy works similarly. The heart wall thickens abnormally, sometimes blocking blood flow out of the heart entirely. Even when there’s no obstruction, the stiffened muscle can’t relax properly, reducing how much blood the chamber holds and sends out with each beat. The thickened muscle demands more oxygen while simultaneously making delivery more difficult, producing chest pain that can feel identical to angina from blocked arteries.
Environmental and Emotional Triggers
Cold weather is one of the most reliable angina triggers, and the mechanism is straightforward. Cold activates your sympathetic nervous system, the same fight-or-flight response you get from fear or stress. Blood vessels near the skin constrict to conserve heat, which can raise blood pressure by 5 to 30 mmHg. Your heart rate climbs as stress hormones like adrenaline surge. The heart is suddenly working harder against greater resistance, and if the coronary arteries are already compromised, they can’t deliver enough blood to match the increased demand.
Physical activity in cold weather is a double hit. Exercise raises heart rate and oxygen demand while the cold simultaneously narrows blood vessels and increases the resistance the heart must pump against. This is why shoveling snow after a winter storm is a classic trigger for angina episodes and heart attacks.
Emotional stress works through the same hormonal pathway. A burst of adrenaline and related stress hormones raises heart rate, blood pressure, and oxygen demand. Heavy meals can also trigger angina because digestion diverts blood flow and makes the heart work harder. Smoking narrows blood vessels directly and increases heart rate at the same time.
How Angina Is Diagnosed
Diagnosis starts with your symptoms and medical history, followed by an EKG and blood tests to rule out a heart attack. From there, imaging tests help identify the cause. Coronary CT angiography is particularly good at ruling out significant blockages, with sensitivity of 95 to 99 percent and negative predictive values of 97 to 99 percent. If a CT scan shows your arteries are clear, there’s a very high chance that obstructive coronary disease isn’t the problem. Nuclear stress tests using PET imaging have sensitivity around 90 percent and specificity of 75 to 84 percent.
The challenge comes when major arteries look normal but you’re still having chest pain. Diagnosing microvascular dysfunction or coronary spasm requires specialized testing during cardiac catheterization, where doctors can measure how the small vessels respond to medications that should cause them to dilate. These tests aren’t performed routinely, which is one reason microvascular angina remains underdiagnosed, particularly in women whose chest pain is sometimes dismissed when standard imaging looks normal.