Potential complications from a heart attack can vary widely, from mild to life threatening.

Some people experience what is sometimes referred to as a "minor" heart attack (although it is still very serious) with no associated complications. This is also known as an uncomplicated heart attack.

Other people experience a major heart attack, which has a wide range of complications and may require extensive treatment.

Some common complications of a heart attack are discussed in more detail below.

Arrhythmia

An arrhythmia is an abnormal heartbeat – this includes beating too quickly (tachycardia), too slowly (bradycardia) or irregularly (atrial fibrillation).

Arrhythmias can develop after a heart attack as a result of damage to the muscles. Damaged muscles disrupt electrical signals used by the body to control the heart. Some arrhythmias, such as tachycardia, are mild and cause symptoms such as:

• palpitations (the sensation of your heart racing in your chest or throat)
• chest pain
• dizziness
• lightheadedness
• fatigue (tiredness)
• breathlessness

Other arrhythmias can be life threatening, such as:

• complete heart block, where electrical signals are unable to travel from one side of your heart to the other, so your heart cannot pump blood properly
• ventricular arrhythmia, where the heart begins beating faster before going into a spasm and stops pumping altogether; this is known as sudden cardiac arrest – see symptoms of a heart attack for more information

These life-threatening arrhythmias can be a major cause of death during the 24 hours after a heart attack.

However, survival rates have improved significantly since the invention of the portable defibrillator – an external device that delivers an electric shock to the heart and "resets" it to the right rhythm.

Mild arrhythmias can usually be controlled with medication such as beta-blockers.

More troublesome arrhythmias that cause repeated and prolonged symptoms may need to be treated with a pacemaker. This is an electric device surgically implanted in the chest, which is used to help regulate the heartbeat.

Heart failure

Heart failure happens when your heart is unable to effectively pump blood around your body. It can develop after a heart attack if muscles in your heart are extensively damaged. This usually occurs in the left side of the heart (the left ventricle).

Symptoms of heart failure include:

• shortness of breath
• fatigue
• swelling in your arms and legs due to a build-up of fluid

Heart failure can be treated with a combination of medications and, in some cases, surgery.

Read more about the treatment of heart failure.

Cardiogenic shock

Cardiogenic shock is similar to heart failure, but more serious. It develops when the heart’s muscles have been damaged so extensively it can no longer supply enough blood to maintain many of the body's functions.

Symptoms include:

• mental confusion
• cold hands and feet
• decreased or no urine output
• rapid heartbeat and breathing
• pale skin

Cardiogenic shock can be treated using blood-thinning medication, which makes the blood easier to pump. A type of medication called vasopressors may be used. Vasopressors help constrict (squeeze) the blood vessels, which increases the blood pressure and improves blood circulation.

Once the initial symptoms of cardiogenic shock have been stabilised, surgery may be required to improve the functioning of the heart. This may still include PCI, alongside the insertion of a small pump, known as an intra-aortic balloon pump. This can help improve the flow of blood away from the heart.

Another option is a coronary artery bypass graft (where a blood vessel from another part of your body is used to bypass any blockage).

Heart rupture

A heart rupture is a serious and relatively common complication of heart attacks, occuring in around 1 in 10 cases.

A heart rupture is where the heart’s muscles, walls or valves rupture (split apart). It can occur if the heart is significantly damaged during a heart attack. It usually happens 1 to 5 days after a heart attack.

Symptoms are the same as those of cardiogenic shock. Open heart surgery is usually required to repair the damage.

The outlook for people who have a heart rupture is not good, and it is estimated that half of all people die within 5 days of the rupture occurring.

Aneurysm

An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.

Blood

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Depression

Depression is when you have feelings of extreme sadness, despair or inadequacy that last for a long time.

Heart

The heart is a muscular organ that pumps blood around the body.

Heart Attack

A heart attack happens when there is a blockage in one of the arteries in the heart.

Inflammation

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Lungs

Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen.

Oxygen

Oxygen is an odourless, colourless gas that makes up about 20% of the air we breathe.

Pain

Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign it has been damaged.

Rupture

A rupture is a break or tear in an organ or tissue.

Tissue

Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Veins

Veins are blood vessels that carry blood from the rest of the body back to the heart.