Know your heartbeat

Heart Rhythms

An abnormal heart rhythm is referred to as an arrhythmia. More than 700,000 people in England alone are affected by an arrhythmia (Department of Health, 2005). An abnormal heart rhythm can cause some people to feel unwell or anxious. Some are more serious than others. Some people may not be aware they have an abnormal heart rhythm, which is why patients often have an ECG (heart tracing) when they attend their outpatient’s appointment. Obtaining appropriate information and support is helpful and can help to improve your quality of life.

The difference between heart rate and heart rhythm The heart rate is the number of times the heart beats in a minute. The heart rhythm is the pattern of the heart beat. It may be referred to as regular, irregular, fast or slow. The normal heart rhythm is called sinus rhythm. The rate is normally between 60 and 100 beats a minute at rest, and it is regular. If you have congenital heart disease your heart rate may be slightly outside these parameters. This does not necessarily mean you have a problem, but will be monitored at your clinic appointments for significant changes.

Explanation of normal conduction system (electrical activity)

The heart has a system of electrically active fibres within it, which are called the conducting system and are responsible for the heart beat. In normal sinus rhythm, the impulse (heart beat) starts in the right side of the upper chambers (atria) of the heart in the sinus node (SA Node in the diagram above). The sinus node can be referred to as the heart’s ‘natural pacemaker’. The impulse then travels across the atria causing the atria to contract squeezing blood into the lower chambers (ventricles). The impulse then arrives at the atrioventricular node (AV Node in the diagram above) right in the centre of the heart. From here the impulse travels through the ventricles via the Purkinje fibres. The impulse travelling through the ventricles causes them to contract resulting in blood being pumped to the lungs and body. It looks like this on a 12 lead ECG.

Symptoms of an abnormal heart rhythm may include palpitations (feeling your heart racing), breathlessness, dizziness, collapse or becoming unconscious. Syncope is the medical term for fainting which is sometimes called vasovagal syncope. Some people are aware of what feel like extra beats or missed beats which are called ectopics. These can feel unpleasant but are not harmful. These are very common and can often be diagnosed. There are many types of abnormal heart rhythms which can be split into two groups:

Slow heart rhythms or ‘bradycardia’ and fast heart rhythms or ‘tachycardia’.

The heart rhythm is normal but it is slow. This occurs when the heart rate drops below 60 beats a minute. Many normal people have this whilst asleep or resting. People who are physically fit often have slower heart rates too. Following heart surgery, some people have slow heart rates, but are fit and well. These are monitored in clinic. Other causes include some drugs, e.g. beta blockers, an underactive thyroid gland, or hypothermia. Symptoms (if any) may include dizziness and collapse.

Treatment is not usually required for bradycardia. If there is an underlying condition causing the bradycardia, this may be treated. A pacemaker may be required if symptomatic.

Heart Block
Heart block occurs when there is a fault within the conducting system fibres causing delay or complete blockage of transmission of the impulse responsible for the heart beat. There are different degrees of heart block (1st, 2nd and 3rd), depending on severity. 1st degree block does not require any treatment. Some 2nd degree block and most 3rd degree blocks require treatment with a pacemaker. Heart block can be seen after cardiac surgery, this is why temporary pacing wires are used.

Fast heart rhythms
Some fast heart rhythms arise from above the ventricles (i.e. in the atria), and some arise from the ventricles themselves. It is important to identify which fast heart rhythm you have so you receive the most appropriate treatment.

Types of fast heart rhythms occurring in the atria tend to be less serious than those occurring in the ventricles although they can cause unpleasant symptoms. These include:

  • Sinus tachycardia
  • Supraventricular tachycardias (SVTs)
  • Atrial flutter
  • Atrial fibrillation

Sinus tachycardia occurs when the heart beats faster than 100 beats a minute. This can occur when you exercise, are anxious or pregnant.

Other reasons for a fast heart rate are:

  • severe anaemia
  • an overactive thyroid gland
  • infection
  • severe blood loss
  • stimulants, e.g. caffeine, nicotine, alcohol
  • prescribed drugs, e.g. salbutamol (Ventolin)
  • illegal drugs such as amphetamines (Speed), cocaine, Ecstasy

Usually there is no indication for treating sinus tachycardia. However, it may be that the cause of the tachycardia requires treatment

Supraventricular tachycardia or SVTs for short is an umbrella term for fast heart rhythms that arise from the atria. They are usually intermittent – i.e. they come and go. The medical term for this is paroxysmal. They can be caused by the presence of one or more extra electrical pathway between the atria and ventricles, or by stretching of the atrial walls. They can cause the heart to beat very fast and in the majority of cases there are no other heart abnormalities. Triggers for SVT in people who are prone to it include caffeine, alcohol, drugs, or hormone changes in adolescence or pregnancy.

Different types of SVTs need different treatments.

Atrial Fibrillation is the most common type of arrhythmia. It is a chaotic irregular heart beat occurring in the atria. It can be very fast and may cause symptoms such as palpitations, breathlessness, chest pain, dizziness and fainting. Approximately 30% of people with AF are asymptomatic (have no symptoms).

Atrial Flutter is a cousin of atrial fibrillation. It occurs when electrical impulses circulate very fast around the atria, often beating at a rate of 150 beats per minute.

There are various tests that can be carried out to try to determine the cause of the arrhythmia. A test can simply mean having a heart tracing tape attached for a period of 24 hours or longer, or you may have a test similar to a cardiac catheter that examines the electrical activity of the heart (Electrophysiology study).

Treatments: people with SVT/atrial fibrillation/atrial flutter may be offered one or more of the following:

  • Intravenous medication
  • Tablets such as beta-blockers, calcium channel blockers and other anti-arrhythmic drugs, which are taken regularly to prevent them reoccuring
  • Cardioversion (a procedure carried out under general anaesthetic, which requires an electrical shock to the heart. This puts the heart back into a normal rhythm)
  • Catheter ablation (a procedure to “burn away” the extra electrical pathway in the heart)

Ventricular tachycardia (VT): This arrhythmia occurs within the ventricles.

If you or your Doctor suspects you have had an episode of VT, you should be referred back to the cardiologist urgently.

VT significantly affects how well the heart pumps so people experiencing VT are often symptomatic. This abnormal heart beat can last for a few seconds or minutes and can self terminate (stop on its own). Symptoms may include palpitations, breathlessness, occasionally chest pains, sweatiness, feeling sick, collapsing. VT can occasionally lead to cardiac arrest.

Causes of VT include heart disease that has caused permanent damage to the heart muscle, previous cardiac surgery or less commonly, inherited genes, e.g. long QT syndrome.

If you become unwell quickly, you may be given intravenous anti-arrhythmic drugs or electrical cardioversion or both.

Long term treatment may include anti-arrhythmic drugs, catheter ablation or you may be considered for the fitting of a device called an Implantable Cardiac Defibrillator, often called an ICD. More information about ICDs can be found on the Arrhythmia Alliance website: www.arrhythmiaalliance.org.uk

Where to get help

If you have concerns or questions relating to your heart condition and potential heart rhythm abnormalities, there are some top tips that may help.

  • Talk to your GP – he/she can contact the Cardiologist directly if concerned.
  • The Cardiac Nurse Specialist based in the Specialist Centre can offer advice and support, and arrange for you to be assessed in the outpatients’ clinic if necessary. Give her/him a ring and explain your symptoms and concerns.
  • If you develop palpitations, it may be helpful for the cardiologist to get an ECG (heart tracing) at your GP practice or local A & E. This can help with diagnosis and treatment if necessary.
  • If you are onedication for heart rhythm disturbances, you may want to carry some information in your wallet or purse in the rare case of an emergency.
  • If you have had problems with arrhythmia, it may be worth carrying a copy of your normal ECG with you.