Uncover the difference between heart attack and sudden cardiac arrest

A heart attack is when the heart is deprived of oxygen due to a blockage in one of the coronary arteries that supplies blood to the heart. A heart attack is also known as a myocardial infarction. The longer that the blockage remains untreated, the greater the damage to the heart. Without oxygen, the heart muscle can start to die, and without treatment to restore blood flow, the heart can be permanently damaged.

A cardiac arrest is when the heart suddenly stops beating. This is also known as a sudden cardiac arrest. When the heart stops beating in a cardiac arrest, it stops pumping blood around the body. Blood flow to the brain and other vital organs stops, and the sufferer loses consciousness and stops breathing normally.

A heart attack and cardiac arrest are not the same thing, although sometimes the terms are used interchangeably. Both are medical emergencies and can be fatal without immediate treatment, but their underlying causes and symptoms are different.

A heart attack is when blood flow to the heart is blocked – the heart stops receiving enough oxygen to work properly, but it is usually still beating. The heart suffers a circulation problem.

A cardiac arrest is when the heart suddenly stops beating, most commonly due to a malfunction in the heart’s electrical system. The heart suffers an electrical problem.

Differences between heart attack and cardiac arrest symptoms

The symptoms of heart attack and cardiac arrest are different, as well as how they are managed and treated.

In a heart attack, the sufferer will usually be awake, breathing and experiencing symptoms of heart attack such as chest pain while their heart continues to beat.

In a cardiac arrest, the sufferer will be unconscious and not breathing normally or breathing at all, and their heart will have stopped beating.

Causes of heart attack

The most common cause of heart attack is coronary heart disease, also known as coronary artery disease. This is where the blood vessels that supply blood to the heart are blocked by fatty plaques.

Atherosclerosis is the process by which these fatty plaques (made up of fat, cholesterol and other substances) build up in the arteries. These plaques can grow bigger over time, narrowing the arteries and causing them to stiffen. This in turn reduces blood flow to the heart, starving it of the vital oxygen it needs to function properly.

If the atherosclerotic plaque breaks away from the artery wall, it can form a blood clot. If a clot blocks an artery to the heart, stopping blood flow to the heart, this can cause a heart attack.

Heart attack can also have other causes, including coronary artery spasms. If a coronary artery has a spasm, blood flow to the heart can be reduced or stopped, and in severe cases this can cause a heart attack.

Causes of sudden cardiac arrest

The heart has an electrical system that controls how it beats and how it pumps blood around the body. If something goes wrong with this system, the heart can beat irregularly (arrhythmia), too fast, too slow, or even stop beating altogether in a cardiac arrest. The main causes of the malfunction that can lead to cardiac arrest include ventricular fibrillation, untreated coronary heart disease that leads to heart failure and cardiac arrest, structural changes and defects in the heart, and inflammation of the heart muscle.

A prior heart attack also increases the risk of a cardiac arrest, either immediately after the heart attack or during recovery.

Other events such as trauma, major blood loss, severe lack of oxygen, electrocution, drowning, allergic reactions and drug overdose can cause a cardiac arrest. However, sometimes the cause of a cardiac arrest is unknown.

While heart attack and sudden cardiac arrest are different medical emergencies, they are linked. A heart attack increases the risk of a cardiac arrest because the person having the heart attack may develop a dangerous heart rhythm that can cause a cardiac arrest. This can occur after the heart attack or during the recovery phase.

If someone suffers a heart attack or shows symptoms of a heart attack, immediately call emergency services. Paramedics treat heart attack as an emergency and will be able to assess the patient and start treatment while on the way to the hospital.

Early treatment is critical to restore blood flow to the heart and prevent further damage to the heart. Without oxygen, the heart muscle can start to die, and without treatment, the heart can be permanently damaged.

If someone suffers a cardiac arrest, immediately call emergency services and start cardiopulmonary resuscitation (CPR) until the paramedics arrive or a defibrillator becomes available. Without immediate treatment, cardiac arrest can lead to death. For every minute that passes after a cardiac arrest without CPR and defibrillation, the chance of survival decreases by up to 10 per cent. In some cases, cardiac arrest can be reversed if treated immediately.

Automated external defibrillators (AEDs) are commonly installed in large public places. They send an electric shock to the heart to help it regain function and beat normally. An AED should be used as soon as possible in cases of cardiac arrest or suspected cardiac arrest – it will not hurt the person it is used on if they are not suffering a cardiac arrest, but it can save their life if they are. AEDs can be used by anyone and do not require prior training, as they provide simple verbal and visual instructions.

The risk of heart attack and sudden cardiac arrest increases with age, and men are at higher risk than women. Because of the link between cardiac arrest and cardiovascular diseases (CVDs) like heart attack, the risk factors for CVD are also risks for cardiac arrest.

Here are some tips to manage these risks and help prevent heart attack and cardiac arrest.

• Smoking: Quit smoking if you smoke. Both first-hand smoking and long-term exposure to second-hand smoke can damage arteries that supply blood to your heart and body and increase the risk of atherosclerotic plaque.
• High blood pressure: High blood pressure can speed up atherosclerosis, damage the arteries leading to the heart and place strain on the heart over time. It can be managed through medication and dietary changes, such as lowering salt intake.

• High cholesterol: High levels of the “bad” cholesterol (LDL cholesterol) can narrow the arteries and add to the build-up of atherosclerotic plaque. Making dietary changes can help manage high cholesterol. High cholesterol mediations are also available.
• Overweight and obesity: Being overweight can increase the risk of heart and health problems, including other risk factors like high blood pressure and high cholesterol. Eating a healthy diet and taking part in regular physical activity can help in reaching and maintaining a healthy weight.
• Inactivity: An inactive lifestyle can contribute to being an unhealthy weight and increase the risk of other risk factors like high blood pressure and cholesterol levels. It’s also important to stay active after a cardiac arrest or after being diagnosed with a CVD, under the guidance of your doctor.
• Diabetes: People living with diabetes are over twice as likely to develop CVD and up to four times more likely to suffer a heart attack. Leading a healthy lifestyle and making certain dietary changes can help manage diabetes.
• Poor nutrition: Try to eat a balanced, nutritious diet for optimal health. Eating a diet high in saturated fat, trans fat, LDL cholesterol, salt and sugar can contribute to being an unhealthy weight and other risk factors for CVD.
• Stress: Make some time for self-care and to destress. Stress in the long term can damage the arteries and worsen other risk factors for CVD.

Learn more about the risk factors for CVD.

HRI is conducting critical research to prevent and treat the cardiovascular diseases and heart conditions like heart attack that can lead to cardiac arrest.

Our Coronary Diseases Group is investigating whether the anti-inflammatory drug colchicine can be repurposed to protect against repeat heart attacks. A collaboration between the Coronary Disease Group and our Clinical Research Group has also discovered that the heart releases certain substances during a heart attack that can be detected in the laboratory.