Second-degree heart block (Mobitz type II): symptoms, tests and pacemakers

Electrical impulses move through the heart and make it beat. The British Heart Foundation explains that an atrioventricular (AV) heart block happens when those impulses are delayed or blocked as they travel between the atria, the top chambers of the heart, and the ventricles, the bottom chambers. There are three degrees of AV heart block: first, second and third (complete).

The NHS says that first-degree block does not usually need treatment, second-degree sometimes needs treatment, and third-degree (complete) often needs treatment. Second-degree block is therefore the middle group, where some beats get through and others are blocked.

Doctors divide second-degree block into subtypes, commonly called Mobitz type I and Mobitz type II, based on the pattern seen on the ECG. The two UK patient sources used for this page describe second-degree block as a group and do not set out the differences between the subtypes in detail, so the information below applies to second-degree block generally. Which subtype you have, and what it means for you, is something a cardiologist reads from your ECG.

The NHS lists dizziness, fainting or feeling like you are about to faint, chest pain, tiredness and shortness of breath. Symptoms can range from mild to severe depending on the type of heart block, and some people have no symptoms and only find out during tests for something else. The BHF adds that some people with heart block can have a very low heart rate, and that in some people the block is always there while in others it can come and go.

The NHS advises getting help from NHS 111 if you feel dizzy all the time or it keeps coming back, you have fainted, or you have shortness of breath that gets worse during normal activities or when lying down. It says to call 999 if you have been diagnosed with heart block and have chest pain, severe difficulty breathing, feel sweaty, sick or lightheaded, or if someone faints and is not breathing or cannot be woken within 1 minute. It advises not driving yourself to A&E.

• Dizziness or light-headedness that keeps coming back.

• Fainting or near-fainting.

• Unusual tiredness, sometimes confusion.

• Chest pressure or pain.

• Shortness of breath.

The NHS says heart block is most often caused by a heart condition such as coronary heart disease, or a heart attack. Other possible causes of AV heart block include some types of medicine, infection and inflammation of the heart caused by another condition, and having heart surgery. Sometimes there is no obvious cause.

The BHF lists coronary heart disease, congenital heart disease, cardiomyopathy, ageing of the electrical pathways in the heart, thickening of the heart muscle and some medicines. It also says heart block can happen naturally in people with a normal heart and no heart problems. If heart block is due to medicines or an imbalance of body salts (electrolytes), the BHF says people are monitored closely in hospital and given treatment to reverse the medicine effect or correct the imbalance.

The main test is an ECG, which measures the electrical activity of the heart. The NHS says it usually takes only a few minutes but you may be asked to wear a portable ECG for 1 or 2 days to monitor your heart, which is useful when the block comes and goes. Other tests that may help include an echocardiogram or MRI scan to see the heart and nearby blood vessels, exercise tests on a bike or treadmill, and blood tests.

The BHF says unless you have symptoms, heart block is often noticed while you are having routine tests for other conditions, and that the ECG result can show the type of block you have.

The NHS says treatment depends on what is causing heart block and whether you have symptoms. If you have heart block that is not causing symptoms you will not usually need treatment. If symptoms are severe you may need a pacemaker, which keeps the heart beating regularly and not too slowly, either for a short time or permanently depending on the cause.

The BHF states that if you are diagnosed with second- or third-degree heart block you may need a pacemaker. If heart block is caused by a heart attack you may only need a temporary pacemaker in hospital, and a permanent pacemaker if the rhythm does not come back to normal shortly afterwards.

If you are diagnosed, the NHS says you can get advice and support from your GP or other healthcare professionals, and from the British Heart Foundation, which runs a Heart Helpline staffed by cardiac nurses. The BHF also publishes a free heart block booklet.

Keep a note of any new dizziness, fainting or breathlessness and report it promptly, because the BHF notes that blocks can progress to a higher degree if untreated. Anyone who has fainted should also ask their doctor about driving.

On the NHS, an ECG is usually arranged by the GP or in hospital, and anyone with fainting or a slow rhythm may be assessed by a cardiology or arrhythmia service. Pacemaker implantation is done in specialist cardiac centres, and emergencies go through 999 and A&E.

Private cardiology offers earlier appointments for ECG monitoring and device assessment, and some people use it for a second opinion. The tests and pacemakers themselves are the same; differences are waiting times and the choice of consultant. If symptoms are severe, do not wait for any appointment.