A heart attack (also known as a myocardial infarction or MI) is caused by blocked blood flow to part of the heart, resulting in damage to heart muscle. Heart attack signs and symptoms can vary greatly, sometimes with immediate and intense chest pain but more often starting slowly with chest tightness and pain that may persist for hours or days.
A heart attack is a serious medical condition that requires emergency treatment to minimise damage to the heart and reduce risk of sudden cardiac arrest. It is crucial to recognise the symptoms of heart attack and call 111 immediately if you think that you or someone you're with might be having a heart attack.
A heart attack is often confused with sudden cardiac arrest. A heart attack is the disruption of blood flow to part of the heart and is not normally fatal. A heart attack does, however, increase the risk of sudden cardiac arrest ie: the disruption of the heart’s pumping action that stops blood flow to the rest of the body and causes loss of consciousness, absence of pulse, and (if the heart cannot be re-started) death.
A heart attack occurs when a narrowing or blockage of a coronary artery prevents the supply of blood and oxygen to a portion of the heart. This is most commonly the result of a condition known as coronary heart disease, where cholesterol and other substances (known as plaque) gradually build up on the inside of coronary arteries.
During a heart attack, a plaque build-up in the coronary artery ruptures, causing a blood clot to form. The clot restricts blood flow through the coronary artery. If large enough, the clot can completely block the flow of blood to the heart. The lack of coronary artery blood flow can result in damage to, or death of, some of the heart muscle.
Other causes of a heart attack are a spasm (contraction) in a coronary artery that blocks blood flow to part of the heart muscle, a tear in the coronary artery, and small blood clots or fat particles that travel from other parts of the body (coronary embolism). A heart attack can also occur if general blood flow to the heart is severely reduced, such as when a person’s body goes into shock as a result of trauma, heatstroke or blood loss.
There are certain factors that contribute to the build-up of plaque, which narrows arteries and increases the risk of having a heart attack. Some, like age, are out a person's control but others can be addressed with lifestyle changes to reduce the chances of having a heart attack:
- Age, men over the age of 45 years and women over the age of 55 years
- A family history of heart attack
- Smoking (and exposure to second-hand smoke)
- High blood pressure
- High blood cholesterol levels
- Diabetes mellitus
- Physical inactivity
Signs and symptoms
The signs and symptoms of a heart attack can vary greatly, as can their severity. Some heart attacks occur suddenly and are intense, but most start slowly with only mild pain or discomfort. As a result many people wait too long before seeking medical attention.
Common signs and symptoms of a heart attack include:
- Pain, which may feel like pressure, tightness, or an aching or burning sensation, across the front of the chest that may spread to the one or both arms (more commonly the left arm), neck, back, jaw, stomach and abdomen
- A feeling of fullness, indigestion, heartburn-like pain or abdominal pain may be experienced
- Nausea and/or vomiting
- Shortness of breath
- Sweating or a cold sweat
- Feeling faint or dizzy
- A feeling of anxiety or impending doom
- Weakness and tiredness.
The first warning of heart attack may be recurrent chest pain, known as angina, which is triggered by physical exertion and relieved by rest. Angina differs from a heart attack; it is caused by a temporary decrease in blood flow to the heart that does not result in damage to heart muscle.
Diagnosis involves medical staff asking about your symptoms and measuring your blood pressure, pulse, and temperature. They will also listen to your heart and lung sounds with a stethoscope and ask about your family history of heart disease. Tests that will help to confirm a heart attack include:
- Electrocardiogram (EGC), which monitors the electrical activity of the heart to reveal injured heart muscle
- Blood tests, to test for the presence of specific proteins that leak into the blood if the heart muscle has been damaged
- Chest x-ray, to check the size of the heart and the coronary arteries
- Echocardiogram, uses sound waves to produce moving images of the heart that reveal abnormalities with the heart
- Coronary angiogram, an x-ray imaging technique to show if the coronary arteries are narrowed or blocked
- Exercise stress test, involves conducting an ECG during exercise since problems with the heart are more likely to be revealed when the heart is working harder
- Cardiac computerised tomography (CT) or magnetic resonance imaging (MRI), involves the use of high-tech machines to reveal problems with the heart and coronary arteries by taking a series detailed images of the heart.
Depending on the severity of the heart attack and the amount of damage to the heart, the use of medications, a surgical procedure, or both may be required for treatment. The main aim of treatment is to restore (and help to maintain) the flow of blood to the heart.
Medications given to treat a heart attack and reduce cardiovascular risk include:
- Thrombolytics (‘clot-busting’ drugs), such as alteplase, to dissolve the clot that is blocking blood flow to the heart
- Aspirin or ‘super aspirins’ such as clopidogrel, or other blood thinning medicines such as heparin, to help prevent new clots from forming
- Pain relievers, such as morphine, to reduce discomfort
- Nitroglycerin to treat chest pain (angina) by temporarily opening arterial blood vessels and increasing blood flow to and from the heart
- Beta blockers, such as carvedilol, which relax the heart by slowing heart beat and reducing the force of the heart’s contractions (beats)
- Angiotensin-converting enzyme (ACE) inhibitors, such as captopril, which lower blood pressure and reduce stress on the heart
- Cholesterol-lowering drugs, called statins, to lower levels of unwanted cholesterol in the blood.
In addition to medications, one of the following surgical procedures may be used to restore blood flow to the heart:
- Coronary angioplasty and stenting: opens blocked or narrowed coronary arteries
- Coronary artery bypass surgery: involves using a blood vessel taken from another part of the body to bypass a blocked or narrowed coronary artery.
The following lifestyle changes can help to prevent a heart attack occurring as well as help recovery from a heart attack:
- Quit smoking and avoid second-hand smoke
- Control high blood pressure or high blood cholesterol levels
- Get regular medical check-ups and take medication as prescribed
- Exercise regularly, especially healthy-heart exercise
- Maintain a healthy weight
- Eat a healthy-heart diet
- Control diabetes
- Reduce stress
- Avoid drinking alcohol or do so in moderation.
Additionally, ‘blood-thinning’ medications, beta blockers, ACE inhibitors, and cholesterol-lowering drugs may be prescribed long term to reduce the risk of a future heart attack.
Further information and support
Free phone: 0800 611 116
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Mayo Clinic (2017). Heart attack (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. http://www.mayoclinic.org/diseases-conditions/heart-attack/basics/definition/con-20019520 [Accessed: 31/08/17]
Mayo Clinic (2017). Sudden cardiac arrest (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. http://www.mayoclinic.org/diseases-conditions/sudden-cardiac-arrest/home/ovc-20164858 [Accessed: 31/08/2017]
Ministry of Health (2017). Heart disease (Web Page). Wellington: New Zealand Government Ministry of Health. http://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/heart-disease [Accessed 31/08/17]
Heart Foundation (2015). Lowering your risk of heart attack and stroke (Pamphlet). Auckland: Heart Foundation of New Zealand. http://assets.heartfoundation.org.nz/shop/heart-healthcare/lowering-your-risk.pdf
O’Toole, M.T. (Ed.) (2013). Myocardial infarction. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Updated: September 2017