A heart attack, also called a myocardial infarction, refers to damage to the heart caused when the blood supply to part of the heart muscle is blocked. A heart attack happens because the blood supply has been cut off following a blockage in a branch of one of the coronary arteries (blood vessels that supply the heart muscle). The faster treatment is started, the less damage is done to the heart muscle.
The most common symptoms associated with heart attack are:
- chest discomfort or pain, often described as a feeling of heavy pressure or tightness or crushing pain in the centre of the chest, or a feeling like indigestion;
- pain, discomfort, tightness or heaviness in the shoulders, neck, arms, back, jaw or throat;
- nausea (feeling sick);
- cold sweat;
- shortness of breath; and
- unusual tiredness (sometimes lasting for days).
Heart attack symptoms vary from person to person – some people have no symptoms, or symptoms can range from mild to severe. They may stop, or get less and then return. Symptoms usually last for more than 10 minutes if you are having a heart attack.
Blockages in coronary arteries are usually the result of 2 processes: the development over many years of fatty plaques in the walls of the coronary arteries, and the formation of a clot on one of the plaques, which can block the flow of blood through the coronary artery. Treatment given early during a heart attack can help to dissolve the clot, reducing damage to the heart muscle.
The process that leads to the narrowing and blockage of the coronary arteries (atherosclerosis) starts as early as adolescence and builds up slowly over the years. No single cause of coronary artery disease has been identified. There are, however, several known risk factors for heart attack. The more risk factors you have, the greater your chance of having a heart attack.
Risk factors include:
- age (heart attack is more likely in men older than 45 and women older than 55 years);
- cigarette smoking;
- unhealthy diet;
- lack of physical activity;
- excess alcohol consumption;
- raised blood cholesterol;
- raised blood pressure (hypertension);
- previous heart disease; and
- family history of heart disease.
Heart attack complications
Damage to the heart muscle resulting from a heart attack can cause complications, including:
- arrhythmias (abnormal heart rhythms, that in some cases can be serious or even fatal);
- heart failure;
- inflammation of the lining of the heart (pericarditis); and
- heart valve problems.
Complications may occur straight away, or take some time after a heart attack to develop.
If you are experiencing symptoms of heart attack, call an ambulance immediately. The faster treatment is started, the better.
To determine whether you could be having a heart attack, paramedics and doctors usually:
- ask about your symptoms and medical history;
- perform a physical examination; and
- do an electrocardiogram (ECG) to check for certain changes associated with heart attacks (an ECG uses electrodes attached to the skin to measure and record the electrical activity in the heart).
If a heart attack is suspected, emergency treatments for possible heart attack may be started straight away.
Other tests that may be performed to confirm the diagnosis of heart attack include:
- blood tests;
- chest X-ray;
- echocardiogram (an ultrasound of the heart that can show how the heart is pumping); and
- coronary angiogram (an X-ray procedure used to detect blockages in the coronary arteries).
Treatment for heart attack works best when it is started as soon as possible after symptoms appear.
Emergency treatment for heart attack is often started before the diagnosis is confirmed and includes:
- oxygen (via a facemask) if oxygen levels are low;
- aspirin (to prevent further blood clotting);
- nitroglycerine (spray or tablets given under the tongue to help open up the coronary arteries and improve blood flow to the heart); and
- pain relievers.
Once the diagnosis of a heart attack has been confirmed, treatment is aimed at restoring blood flow to the heart muscle to prevent or reduce permanent damage to the heart.
- Thrombolysis (also called fibrinolytic therapy) involves injecting medicines that dissolve the clot in the coronary artery and help restore blood flow.
- Coronary angioplasty (also called percutaneous coronary intervention) is a procedure that can be performed to unblock the coronary arteries. It involves the insertion of a long, thin, flexible tube called a catheter into a blood vessel, usually in the groin, which is then threaded through to the coronary arteries. Once the blockage in the coronary artery is found, a balloon on the end of the catheter can be inflated to open up the blood vessel. Sometimes a stent (a thin tube) is placed in the coronary artery to keep it open.
- Coronary artery bypass surgery is major heart surgery. It involves using a vein or artery graft to bypass the blocked coronary artery and provide a new channel through which blood can flow.
- Medicines such as beta-blockers, angiotensin-converting enzyme (ACE) inhibitors and statins (cholesterol-lowering medicines) are commonly started in hospital to help your heart recover from a heart attack.
- A cardiac rehabilitation programme may be recommended by your doctor to help you recover from a heart attack and to reduce your chances of having another heart attack. These programmes are usually started in hospital and continue for several weeks after you return home.
Lifestyle measures that can help reduce your risk of having a heart attack include:
- eating a healthy diet;
- getting regular physical activity;
- not smoking;
- maintaining a healthy weight;
- if you drink alcohol, having no more than 2 standard drinks per day.
In addition, treating any conditions (such as high blood pressure, diabetes or high cholesterol) that increase your risk of heart disease can help reduce your risk of heart attack.
2. Acute coronary syndromes (revised February 2012). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2014 Nov. http://online.tg.org.au/complete/ (accessed Mar 2015).
3. National Heart, Lung, and Blood Institute (NHLBI). Heart attack (updated 17 Dec 2013). http://www.nhlbi.nih.gov/health/health-topics/topics/heartattack# (accessed Mar 2015).
4. MayoClinic.com. Heart attack (updated 15 Nov 2014). http://www.mayoclinic.org/diseases-conditions/heart-attack/basics/definition/con-20019520 (accessed Mar 2015).
5. Cabello JB, Burls A, Emparanza JI, Bayliss S, Quinn. Oxygen therapy for acute myocardial infarction. Cochrane Database of Systematic Reviews 2013, Issue 8. http://www.cochrane.org/CD007160/VASC_routine-use-of-oxygen-in-people-who-have-had-a-heart-attack (accessed Mar 2015).