How a Heart Attack Happens

What happens

• The heart muscle is fed by its own arteries, the coronary arteries.
• Plaque (atherosclerosis) builds up in artery walls quietly, often for decades.
• Most heart attacks begin when a plaque's thin cap cracks and a blood clot forms on it, blocking the artery.
• Heart muscle can start to die within about 20 minutes without blood flow. Time is muscle.

Know the warning signs

• Chest pain, pressure or squeezing
• Pain spreading to the arm, jaw, neck or back
• Shortness of breath
• Cold sweat, nausea or light-headedness

Women, older adults and people with diabetes are more likely to have these less obvious symptoms. Call 9-1-1 or your local emergency number right away. Don't drive yourself.

Call 9-1-1 or your local emergency number.

What you can do

• Don't smoke. Within one to two years of quitting, heart-attack risk drops sharply.
• Know your numbers: blood pressure, cholesterol and blood sugar can all be treated.
• Aim for about 150 minutes of brisk activity a week.
• Eat plenty of vegetables, fruit, whole grains, beans, nuts and fish; less salt and processed food.
• Look after your sleep and stress.

Common questions

What is the difference between angina and a heart attack?

Angina is chest pain that happens when a narrowed artery can't deliver enough blood during exertion; it usually eases with rest and doesn't damage the heart muscle by itself. A heart attack happens when an artery is suddenly blocked, usually by a clot on a cracked plaque, and heart muscle starts to die. New, worsening or rest angina needs urgent medical attention.

Can you have a heart attack without chest pain?

Yes. Some people, especially women, older adults and people with diabetes, have shortness of breath, nausea, a cold sweat, light-headedness, or pain in the jaw, neck, back or arm without much chest pain. If the symptoms are new and you're worried, call 9-1-1 or your local emergency number.

Why shouldn't I drive myself to the hospital?

Paramedics can start treatment on the way, check your heart rhythm, send an ECG ahead so the hospital team is ready, and treat a dangerous rhythm if it happens. Driving yourself, or waiting for a lift, delays all of that, and every minute counts because time is muscle.

Transcript

Your heart beats about a hundred thousand times a day. It never takes a day off, and it asks for very little in return.

But it does need one thing, all the time: a steady supply of oxygen-rich blood. When that supply is suddenly cut off, that's a heart attack. Let's see how it happens, and how to prevent one.

Your heart is a muscular pump, about the size of your fist. With every beat, it pushes blood out to the rest of your body.

But the heart can't feed itself from the blood passing through it. It has its own supply lines: small arteries that wrap around the outside, like a crown. They're called the coronary arteries.

Think of them like garden hoses watering a lawn. Pinch one hose, and the patch of grass it feeds begins to wilt.

Inside, a healthy artery is smooth and wide open, so blood flows through easily.

But over many years, fatty deposits can build up inside the artery wall. This build-up is called plaque, and the process is called atherosclerosis.

A plaque has a soft core of cholesterol and inflammatory cells, sealed under a thin, fibrous cap. A bit like a pimple in the artery wall.

It can start as early as our teens and twenties, and grow quietly for decades, usually with no symptoms at all.

When a plaque narrows an artery a lot, the heart can run short of blood during exertion. That can cause chest pain called angina. It's a warning sign worth getting checked.

But here's the surprising part. Many heart attacks start at plaques that weren't blocking much of the artery at all. So what goes wrong?

The thin cap cracks open. The body treats the crack like a cut, and rushes to seal it.

Sticky blood cells called platelets pile onto the crack, and a blood clot forms, right inside the artery.

Within minutes, the clot can block the artery completely. That's a heart attack. Doctors call it a myocardial infarction.

Beyond the blockage, the heart muscle is starved of oxygen. In as little as twenty minutes, muscle cells begin to die, and the damage spreads for as long as the artery stays closed.

That's why doctors say: time is muscle. The sooner the artery is opened, the more heart muscle is saved.

So know the warning signs. Chest pain, pressure or squeezing, often spreading to the arm, jaw, neck or back.

There may also be shortness of breath, a cold sweat, nausea or light-headedness. Women, older adults and people with diabetes are more likely to have these less obvious symptoms.

If you think someone is having a heart attack, call 9-1-1 or your local emergency number right away. Don't drive yourself. The dispatcher may tell you to chew an aspirin.

In hospital, the team works fast to reopen the artery. Often, a thin tube is threaded to the blockage, a tiny balloon opens it, and a mesh tube called a stent holds it open.

Now for the good news. A large study of heart attacks in fifty-two countries found that about nine in ten were linked to risk factors we can change.

The biggest one you control is smoking. Within one to two years of quitting, the risk of a heart attack drops sharply.

Next, know your numbers. High blood pressure, high cholesterol and high blood sugar all damage artery walls, and all of them can be treated.

Keep moving. Aim for about a hundred and fifty minutes of brisk activity a week. That's just over twenty minutes a day.

Fill your plate with vegetables, fruit, whole grains, beans, nuts and fish, with less salt and fewer heavily processed foods. And look after your sleep and stress, too.

One common myth is that heart attacks are mostly a man's problem. In fact, heart disease is a leading cause of death for women, too.

So, to recap. Plaque builds quietly. A crack triggers a clot. The clot blocks blood flow. And fast action saves heart muscle.

Now you know how a heart attack happens, and how to protect your heart. Look after it. It's been working for you all day.

Sources

1. Yusuf S et al. INTERHEART study. Lancet 2004;364:937–952
2. Thygesen K et al. Fourth Universal Definition of Myocardial Infarction. Circulation 2018
3. Libby P et al. Atherosclerosis. Nat Rev Dis Primers 2019;5:56
4. American Heart Association — Warning Signs of a Heart Attack
5. Heart & Stroke Foundation of Canada — Signs of a heart attack
6. CDC — Benefits of Quitting Smoking
7. WHO Guidelines on Physical Activity and Sedentary Behaviour (2020)