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Complications - Heart attack

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

Some people experience a "minor" heart attack (although it can still be 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 potential complications and may require extensive treatment.


An arrhythmia is an abnormal heartbeat and can include:

Arrhythmias can develop after a heart attack as a result of damage to the heart muscles. Damaged muscles disrupt electrical signals that control the heart.

Some arrhythmias, such as tachycardia, are mild and cause symptoms such as:

Other arrhythmias can be life threatening, including:

  • 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 completely; this is known as sudden cardiac arrest

These life-threatening types of arrhythmia can be a major cause of death during the 24 to 48 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 medicine such as beta-blockers.

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

Find out more about sudden cardiac arrest from the charity Sudden Cardiac Arrest UK.

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 your heart muscle is extensively damaged. This usually happens in the left side of the heart (the left ventricle).

Symptoms of heart failure include:

  • breathlessness
  • tiredness (fatigue)
  • swelling in your arms and legs due to a build-up of fluid

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

Find out more about treating heart failure.

Cardiogenic shock

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

Symptoms include:

  • mental confusion
  • cold hands and feet
  • a decreased need to pee or not peeing at all
  • rapid heartbeat and breathing
  • pale skin
  • difficulty breathing

A type of medicine called vasopressors (or inotropes) may be used. Vasopressors help squeeze (constrict) the blood vessels, which increases 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 include percutaneous coronary intervention (PCI), alongside the insertion of a small pump, known as an intra-aortic balloon pump. This can help improve the flow of blood 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 an extremely serious but relatively uncommon complication of a heart attack where the heart's muscles, walls or valves split apart (rupture).

It can happen if the heart is significantly damaged during a heart attack and usually happens 1 to 5 days afterwards.

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 poor; it's estimated that 1 in 2 people die within 5 days of the rupture occurring.

Page last reviewed: 28 November 2019
Next review due: 28 November 2022