Your turn
Each lab is one step from the video. Change things and see what happens.
Each lab isolates one part of the story. The models are simplified to show the idea; they are not medical tools.
Tap the buttons and slide the sliders.
Send the heart for a run, then let it rest. Why does it speed up?
Working muscles demand more oxygen, so the heart rate rises during exercise and falls again at rest.
Go for a run! Then rest. What does the heart do?
Tap a branch. Which part of the heart does it feed?
Each coronary branch supplies its own territory, so where a blockage sits decides which muscle is at risk.
Tap a pipe. Which part of the heart gets its blood?
A simplified map; real coronary arteries vary from person to person.
Slide through the years and switch risks on and off. How fast does the channel narrow?
More risk factors, faster plaque buildup: a qualitative picture of how the lumen narrows with age.
Slide the years. Tap the buttons. Does the pipe get narrow?
A simple picture of the idea, not a real risk calculator.
Crack the plaque. What happens to the muscle beyond the clot?
A ruptured plaque triggers a clot; once the artery is blocked, the muscle downstream is starved of oxygen, and time matters.
Tap to crack it. Can the blood get through?
Step through it: wire, balloon, stent. When does the blood flow again?
A catheter and wire reach the blockage; a balloon squashes the plaque and a stent holds the artery open.
Tap the steps in order. Can you open the pipe?
If someone might be having a heart attack, call 911 / emergency services right away. This isn't medical advice.
Pick some habits, then fast-forward to 65. How open is the artery?
Because plaque builds over decades, habits started young shift the long-run picture.
Tap the good habits, then fast-forward. Is the pipe still open?
A teaching model, not a risk calculator.
Your heart is a muscle about as big as your fist. It squeezes all day and all night to push blood around your body.
The heart needs blood too. Little pipes on the outside of the heart bring it. They spread out like the branches of a tree.
Over many, many years, sticky stuff can build up inside the pipes. The pipes get narrow. Smoking and not moving much make it build up faster.
Sometimes the sticky stuff cracks. The blood makes a plug to fix it, like a scab. But the plug can block the pipe. Then part of the heart does not get enough blood. That is a heart attack. It mostly happens to grown-ups.
Helpers come fast when you call. At the hospital, doctors can often open the pipe with a tiny balloon, so the blood flows again.
Run, jump and play every day. Eat lots of fruit and vegetables. And never smoke.
Please note: This page explains how the body works; it isn't medical advice. If someone might be having a heart attack, call 911 / emergency services (your local emergency number) right away.
Your heart is a muscle, and like every muscle it needs its own supply of oxygen-rich blood. It gets that blood from the coronary arteries, small pipes that branch off the aorta and spread over the outside of the heart.4
Most heart attacks are caused by coronary artery disease.29 Over many years, a waxy mix of fat, cholesterol and other substances called plaque builds up in the walls of these arteries.26 Then one day, a plaque cracks open. A blood clot forms on the crack, and if it grows big enough it blocks the artery.212 The patch of heart muscle beyond the blockage is starved of oxygen, and if blood flow isn't restored quickly, that muscle begins to die. That is a heart attack, or in medical words a myocardial infarction.115
plaque builds up → plaque cracks → clot blocks the artery → muscle starved of oxygen
The heart is a muscle about the size of your fist.16 It beats about 100,000 times a day, and over a long life it can beat more than 3.5 billion times.16 Even though the heart is always full of blood, that blood rushes straight through its chambers. The muscle itself is fed by the coronary arteries, which branch off the aorta, the big artery that carries blood from the heart to the rest of the body.4
| Artery | Branches from | What it mainly feeds |
|---|---|---|
| Right coronary artery | The aorta | The right atrium and parts of both ventricles |
| Left coronary artery | The aorta | The left side of the heart; splits into the two branches below |
| Left anterior descending | Left coronary artery | Parts of both ventricles, at the front |
| Circumflex | Left coronary artery | Part of the left ventricle |
Source: NHLBI.4 Because each branch feeds its own area, how much of the heart is hurt in a heart attack depends on which artery is blocked and how long it stays blocked.6
The slow buildup of plaque is called atherosclerosis.25 It starts with damage to the inner lining of an artery. Cholesterol and cell waste collect at the damaged spots, and white blood cells gather there too, clumping into plaque.5 As the plaque grows, the channel inside the artery gets narrower.
Plaque often starts to form in childhood and gets worse with age.5 In its early stages it usually causes no symptoms at all.6 When an artery becomes very narrow, the heart may not get enough blood when it works hard, which can cause chest pain called angina.2
In the player above, the "years" slider is a simple picture of this idea, not a real risk calculator: more risk factors make plaque build up faster.
Risk factors are things that make coronary artery disease, and so a heart attack, more likely.2 About half of all Americans have at least one of three key ones: high blood pressure, high cholesterol, or smoking.9
| Risk factors you can change | Risk factors you can't change |
|---|---|
| Smoking | Age (risk rises for men after 45 and for women after 55) |
| High blood pressure | Family history of early heart disease |
| High blood cholesterol | |
| High blood sugar or diabetes | |
| Not enough physical activity | |
| Diet high in saturated fat or salt; overweight |
Source: NHLBI.2 Heart attacks mostly happen to adults, but the habits that protect arteries start when you're young.5
Here is the moment itself, step by step.2615
Not every heart attack follows this pattern. Less often, a sudden spasm (tightening) of a coronary artery, a tear in its wall, or a clot that travels from somewhere else can block the blood flow.29
People often mix these up. The American Heart Association puts it simply: a heart attack is a circulation problem, and sudden cardiac arrest is an electrical problem.7
| Heart attack | Sudden cardiac arrest | |
|---|---|---|
| What goes wrong | A blocked artery stops blood reaching part of the heart muscle | The heart's electrical rhythm fails and it can't pump |
| Is the heart beating? | Usually yes | No; the person collapses and has no pulse |
| What to do | Call emergency services right away | Call emergency services, start CPR, use a defibrillator (AED) |
The two are linked: a heart attack can lead to cardiac arrest.17
Heart attacks don't always look like the movies. Some are sudden and intense; others start slowly with mild discomfort that comes and goes.38 Common warning signs include:89
Women are more likely to have signs such as unusual tiredness, nausea or shortness of breath.89 And about 1 in 5 heart attacks are "silent": the damage happens, but the person doesn't notice it.10
What to do: call your local emergency number right away, even if you're not sure. Don't drive to the hospital; emergency teams can start treatment as soon as they arrive.38
The goal is to get blood flowing again as fast as possible.1 A common treatment is coronary angioplasty.13
Other treatments include medicines that help dissolve clots and bypass surgery, which routes blood around a blocked artery.1215 Many people survive a heart attack and go on to live active, full lives.1
Because plaque builds slowly over years, everyday habits make a real difference.211
Starting healthy habits young raises the chance of good heart health into middle and older age.5
Most heart attacks are caused by coronary artery disease. Over years, fatty plaque builds up inside the arteries that feed the heart muscle. If a plaque cracks, a blood clot forms on it and can block the artery. Less often, a sudden spasm or a tear in a coronary artery is the cause.
Blood flow through a coronary artery is suddenly blocked, usually by a clot on a cracked plaque. The patch of heart muscle that artery feeds stops getting enough oxygen. The longer the blockage lasts, the more of that muscle is damaged, which is why fast treatment matters.
The most common sign is pain, pressure, squeezing or fullness in the chest that lasts more than a few minutes or comes and goes. Pain can spread to one or both arms, the back, neck, jaw or stomach, often with shortness of breath, a cold sweat, nausea or light-headedness. Some people, more often women, mainly feel unusual tiredness or sickness. If you think someone might be having a heart attack, call your local emergency number right away.
No. A heart attack is a circulation problem: a blocked artery starves part of the heart muscle, and the heart usually keeps beating. Cardiac arrest is an electrical problem: the heart's rhythm fails and it suddenly stops pumping. A heart attack can sometimes lead to cardiac arrest.
It's less likely, but yes. Plaque can build up for years with no symptoms, and some heart attacks have other causes, such as a coronary artery spasm or tear. Family history also plays a part. Healthy habits greatly lower the risk but can't remove it completely.
Don't smoke, stay active, eat plenty of fruit and vegetables with less salt and saturated fat, and keep a healthy weight. Adults should also keep blood pressure, cholesterol and blood sugar in check with their doctor. Starting these habits young helps keep arteries healthy for life.
Yes. According to the CDC, about 1 in 5 heart attacks are 'silent': the heart muscle is damaged, but the person isn't aware it happened. Symptoms can be mild or unusual.