The difference between a heart attack versus cardiac arrest is one of the most commonly misunderstood distinctions in emergency medicine — and one of the most important. Although the two terms are often used interchangeably in the media and everyday conversation, they describe completely different medical events, with different symptoms, different emergency responses, and very different outcomes.
What Is a Heart Attack?
A heart attack — medically known as a myocardial infarction (MI) — occurs when the blood supply to part of the heart muscle is suddenly blocked, usually by a blood clot forming in a coronary artery that has been narrowed by a build-up of fatty deposits (atherosclerosis). Without blood and oxygen, that section of heart muscle begins to die.
Crucially, during a heart attack the heart is still beating and still pumping blood around the body. The person remains conscious and continues to breathe. Common symptoms include chest pain or tightness, pain radiating to the arm, jaw, or back, breathlessness, nausea, and cold sweats. Some heart attacks — particularly in women — present with more subtle symptoms. Heart attacks require urgent hospital treatment, typically coronary angioplasty and stenting to restore blood flow, but the person is usually awake and responsive throughout.
In the UK, roughly 70–80% of people who have a heart attack survive. The NHS and the British Heart Foundation both provide comprehensive guidance on heart attack symptoms and treatment.
What Is a Cardiac Arrest?
A cardiac arrest occurs when the heart suddenly stops pumping blood around the body altogether. It is an electrical problem rather than a plumbing problem: a dangerous arrhythmia — most commonly ventricular fibrillation — causes the heart to quiver chaotically rather than beat in a coordinated rhythm. The result is that no blood reaches the brain or vital organs.
Someone in cardiac arrest collapses suddenly, loses consciousness immediately, and stops breathing normally. Without intervention, brain damage begins within minutes and death follows rapidly. Survival depends entirely on immediate CPR and defibrillation — which is why the chain of survival is so critical. In the UK, fewer than one in ten people survive an out-of-hospital cardiac arrest. See our cardiac arrest statistics page for the full picture.
Heart Attack Versus Cardiac Arrest: Key Differences
The core distinction when comparing a heart attack versus cardiac arrest comes down to this: a heart attack is a circulation problem; a cardiac arrest is an electrical problem. In a heart attack, the heart muscle is being damaged by a blocked artery but the heart is still working. In a cardiac arrest, the heart has stopped working entirely.
| Heart Attack | Cardiac Arrest | |
|---|---|---|
| Heart still beating? | Yes | No |
| Person conscious? | Usually yes | No |
| Still breathing? | Yes | No (or only agonal gasps) |
| What to do | Call 999, keep calm, do not leave alone | Call 999, start CPR immediately |
| UK survival rate | ~70–80% | ~8–10% |
Can a Heart Attack Cause a Cardiac Arrest?
Yes — this is where the two conditions are genuinely linked, and where the statistics deserve careful handling.
At the level of underlying disease, coronary artery disease (CAD) — the same process that causes heart attacks — is present in around 60–70% of cardiac arrest patients. Years of narrowed, diseased coronary arteries create a heart that is far more prone to fatal arrhythmias. This is the source of the commonly cited figure that roughly 70–80% of cardiac arrests involve coronary artery disease as an underlying factor.
But that is not the same as saying 70–80% are caused by an active heart attack. The distinction matters. A cardiac arrest can occur in someone with severe underlying CAD without an acute blockage happening at that moment — the heart fibrillates due to chronic damage, electrical instability, or other triggers, not necessarily a fresh infarction. More recent evidence suggests that an acute MI as the direct precipitating trigger is present in only around 30% of out-of-hospital cardiac arrests, and the figure has been declining as treatment of coronary disease has improved.
This means a significant proportion of cardiac arrests — including those in younger people, and those with inherited arrhythmias or cardiomyopathies — occur in hearts with little or no coronary disease. For many SCA UK members, the arrest came without prior warning and without the classic “blocked artery” story.
Why the Confusion Between Heart Attack and Cardiac Arrest Matters
The conflation of these two terms is not just a linguistic nuisance — it has real consequences. When the media reports a cardiac arrest as a heart attack (which happens routinely), it distorts the public’s understanding of how cardiac arrest happens, what the warning signs are, and crucially, what bystanders should do when they witness one. A person who sees someone collapse and thinks they are having a heart attack may wait for an ambulance rather than start CPR immediately — a decision that can cost a life.
It also affects survivors. Many SCA UK members were initially told they had a heart attack — by well-meaning family members, friends, or even in initial clinical communications — when they had in fact suffered a cardiac arrest. These are different experiences, with different psychological impacts, different treatments, and different long-term implications. For more on this, see our page on how the media misreports cardiac arrest.
What to Do in an Emergency
The emergency response differs significantly between the two conditions:
If you think someone is having a heart attack: Call 999 immediately. Help them to sit or lie in a comfortable position. If they are not allergic and are able to swallow, they may be advised by the 999 operator to chew an aspirin. Do not leave them alone. Keep them calm and reassured until the ambulance arrives.
If you think someone is in cardiac arrest (unconscious, not breathing normally): Call 999 immediately and start CPR without delay. Push hard and fast in the centre of the chest — 30 compressions, then 2 rescue breaths if you are trained and willing, or continuous chest compressions if not. Use an AED as soon as one is available. Every minute without CPR and defibrillation significantly reduces the chance of survival. CPR training is free and widely available — knowing how to do it could save someone’s life.
Video Explanations
These two short videos explain the difference between a heart attack and a cardiac arrest in accessible, non-clinical language.
See also: What Is Cardiac Arrest?, The Chain of Survival, CPR Training, Arrhythmia, Cardiac Arrest Statistics, and How the Media Misreports Cardiac Arrest.