Technical Terms

Alcohol septal ablation

If you have HCM that makes you breathless, dizzy or suffer chest pain, this may be due to blockage of the flow of blood from the main pumping chamber in the heart due to thickening of the heart muscle. An injection of alcohol into the blood vessel supplying this bit of muscle can help to reduce the obstruction and improve symptoms. This can be done at the time of coronary angiography (see page XX).

Angiography and angioplasty

During coronary angiography the coronary arteries (the arteries that supply blood to the heart muscle) are injected with a dye to reveal any furring or blockages. This can then be treated with a catheter to open up any narrowing by blowing up a balloon at the narrowing (known as angioplasty) and inserting a metal tube (stent) to keep the artery open.

Antiarrhythmic drugs

A group of medicines used to regulate and control the heart’s rhythm. They may be of use in specific situations in people with LQTS (e.g. mexiletine). Ajmaline and flecainide are used in tests used to diagnose Brugada syndrome.


The major blood vessel that leaves the left side of the heart. It supplies blood to the body.

Aortic valve

The valve through which blood passes from the heart into the aorta. The aortic valve is composed of three cusps. A bicuspid valve (a valve that has only two cusps or ‘flaps’) fails to open properly due to the absence of the third cusp and can narrow up due to repetitive damage.


A disturbance of the heart’s rhythm. A ‘ventricular’ arrhythmia can be life threatening.


When the heart’s rhythm stops completely because there is no electrical activity.


Of or belonging to the atria.

Atrial fibrillation

An arrhythmia involving the atria (the two upper chambers of the heart).


One of the two top chambers of the heart. (The plural of ‘atrium’ is ‘atria’.)


A post-mortem examination of a dead body.

AV block

See ‘heart block’.

Atrioventricular (AV) node

The part of the heart that lies between the top chambers (atria) and bottom chambers (ventricles). It regulates the transmission of electrical impulses from the natural pacemaker in the atrium to the ventricle. It helps to prevent the heart from pumping too fast if the impulses from the atrium become too rapid.


Slowing of the heart rate.


‘Of the heart’ or ‘belonging to the heart’.

Cardiac arrest

The state of the heart when it is pumping so erratically or ineffectively that there is no significant blood pressure to supply the heart and brain. If the problem is not resolved within two minutes there will be permanent brain damage, and if left untreated the person will quickly die.


A doctor who specialises in the heart.


Disease of the heart muscle, which is usually inheritable.

Cardiopulmonary exercise test

An exercise test that monitors the consumption of oxygen, using a set of breathing tubes.

Cervical sympathectomy

A form of surgery that is useful for some people with LQTS. It reduces the amount of adrenaline and its by-products produced and delivered to the heart by certain nerves (the left cervical ganglia). It involves operating on the left neck and removing or blocking these nerves, which are not essential to normal function. The procedure can be relatively short but it does need a general anaesthetic.


Conditions characterised by defective ion channels in the cells of the heart.

Computed tomography (CT)

An imaging technique where three-dimensional images are produced using a series of two-dimensional X-ray images.

Congenital heart disease

Disease of the heart, present from birth.

Coronary artery disease

Narrowings and blockages of the arteries supplying the heart muscle, due to ‘furring of the arteries’. Also known as ‘arteriosclerosis’.


The government-appointed legal person responsible for ensuring that no foul play has occurred when an unexpected death happens.


A device used if a person has a cardiac arrest. It may be able to return the heart to a normal rhythm by delivering an electrical ‘shock’ through the chest wall.

Delta wave

The ECG feature characteristic of Wolff-Parkinson-White (WPW) syndrome.


The genetic code from which proteins – ‘the building blocks of life’ – are made. We all receive a copy of half of each of our parents’ DNA when the egg and sperm meet to conceive a new human being.

Ectopic beat

An ‘extra’ beat which occurs when the heart activates prematurely, disrupting its normal rhythm. The heart’s natural pacemaker resumes its normal control after a brief pause. Most of the time the person does not notice these extra beats but, if they do become aware of them, the sensation depends on how close the ectopic beat occurs to the preceding normal beat. If it is close, only the pause might be noticed. If it occurs further away, it might be felt as an extra beat from the heart, making the rhythm feel irregular or erratic.

Electrical cardioversion

A Cardioversion is a procedure that can help your heart rhythm get back to its normal rhythm (called sinus rhythm) if you have persistently abnormal rhythm such as atrial fibrillation or atrial flutter.


The fast irregular contraction of muscle fibres in the heart


The segment of DNA responsible for the production of a specific substance such as a protein that in turn forms the basis for the body to exist and function.

Heart attack

When the heart muscle is damaged by an artery becoming blocked and depriving part of the heart of oxygen. This is caused mainly by coronary artery disease. (A heart attack is also called a ‘myocardial infarct’)

Heart block

A failure of the heart’s electrical impulses to conduct properly from the top chambers (atria) to the bottom chambers (ventricles) via the atrioventricular (AV) node. The severity of the condition and its associated risk can vary.

Heart failure

The reduced pumping function and efficiency of the heart muscle resulting in the body not being supported properly by the heart muscle. This can result in breathlessness and oedema.

Implantable cardioverter defibrillator (ICD)

Figure 9: ICD (implantable cardioverter defibrillator).
An ICD is similar to a pacemaker but the lead to the ventricle is larger, to allow it to deliver a larger shock to the heart when necessary.

A metal electronic device similar to a pacemaker (see below). It can regulate the rhythm of the heartbeat, like a pacemaker does. If a dangerous arrhythmia occurs, the ICD can deliver a shock to the heart. Some people have described the shock as feeling like having a ‘kick in the chest’. An ICD is larger than a pacemaker and may have to be positioned under the chest wall muscle at the left shoulder. The procedure usually takes 1½ to 2 hours and may require a general anaesthetic. The ICD clinic checks are needed once every 3 to 6 months. The battery lasts up to 5 years. When a new battery is needed, the box containing it can be replaced easily.


A chemical substance (such as sodium or potassium) that carries an electrical charge and forms the basis of the movement of electricity through the heart muscle.

Ion channel

The route that ions take in and out of the heart muscle cells to allow movement of electricity.

Magnetic resonance imaging (MRI)

An MRI uses a magnetic field and radio waves to create pictures of tissues, organs and other structures inside the body.

Mitral valve

This is the valve on the left side of the heart, between the atrium and ventricle.

Mitral valve prolapse (MVP)

When the heart is seen on an echocardiogram, the mitral valve can appear ‘floppy’. This is very common, and affects around 1 or 2 in every 100 people. It can become more severe and the valve can become thickened and leaky. Only in rare cases it can be inherited in a family and may be associated with arrhythmia.


The sound of the turbulent flow of blood in the heart, sometimes due to leakage through or narrowing of valves. It can be heard through a stethoscope.


An abnormality or ‘mis-spelling’ of the DNA code that causes its eventual product (usually a protein) to function abnormally, which in turn is responsible for a disease. A ‘sporadic’ mutation is not inherited from a parent’s DNA but occurs due to damage to the DNA after the egg or sperm that forms a human embryo is made.


Swelling of the ankles, legs and even abdomen due to the collection of fluid under the skin in patients with severe cardiomyopathy, particularly DCM. It is caused by increased pressure of blood returning to the heart from the body but not being pumped efficiently by the heart due to heart failure.

Figure 10:Pacemaker.
The leads are connected both to the top chamber (atrium) and the bottom (ventricle) chamber.


A small metal electronic device with internal batteries. It sits under the skin at the left shoulder. It is attached to the top and bottom chambers of the heart by two electrical leads that are inserted via the large veins near the shoulder. These leads both monitor the heart rhythm and allow treatment to be delivered to the heart. Sometimes only one chamber (the ventricle) is connected. A pacemaker can be inserted under local anaesthetic through a small 2-inch cut in the skin. The procedure takes between 45 minutes and 1 hour.

The device is programmed to prevent the heart from slowing down too much by giving tiny imperceptible shocks that activate the heart, independently from the heart’s natural pacemaker. The pacemaker’s battery, the leads and the programming are monitored once every 6 to 12 months in a Pacing clinic, using a special magnet and computer software. The battery lasts 5-10 years. When a new battery is needed, the metal box is replaced – a simple procedure that can be performed through the old scar.


A fast heart beat that may be felt as the heart pounding regularly or irregularly.


A doctor trained to examine the body after death, and samples of its organs, in order to diagnose any abnormalities.


The examination of a dead body by a pathologist.


A patient’s outlook. In this context it means the likelihood of any life threatening events.

Prolonged repolarisation

When repolarisation is slower than normal, the time taken for it to occur is described as prolonged. This can be represented on the ECG by abnormalities of T waves and an increase in the QT interval.

Pulmonary embolus (PE)

In certain circumstances a large clot can form in the deep veins of the legs – for example after long periods of immobility. The clot can dislodge and travel though the veins to the heart where it can block the arteries supplying the lungs and stop the flow of blood to the body. This can cause a sudden collapse and a rapid death. (Also called ‘thromboembolism’.)

QT interval

An ECG measure of repolarisation from the beginning of the QRS to the end of the T wave.

Radiofrequency (RF) ablation

The use of high frequency radio waves to ‘burn’ away small areas of heart tissue such as the extra or ‘accessory’ pathways seen in Wolff-Parkinson-White syndrome or areas that cause arrhythmia in ARVC.


The electrical resetting of the heart muscle ready for its next activation. The time taken is measured by the QT interval.

Sinoatrial (SA) node

The sinoatrial node generates the normal or sinus rhythm of the heart. It is impulse generating tissue that acts as a pacemaker. It is located in the right atrium of the heart.

Sudden cardiac death (SCD)

A death is described as sudden when it occurs unexpectedly, spontaneously and/or even dramatically. If the death is due to heart disease it is called sudden cardiac death (SCD). Some will be unwitnessed or occur during sleep, while others occur during or immediately after exercise (exercise-related sudden cardiac death or ERSCD).


A piece of equipment which a doctor uses to listen to the heart and chest.

Surgical myectomy

This is a treatment for HCM that involves removing small amounts of over developed heart muscle to reduce any blockage in blood flow in the heart.


A collection of medical features of an illness that make it a distinctive condition.


A rapid heart rate.


See ‘pulmonary embolus’ above.


The scientific study of the effects of substances (drugs and chemicals) on the body and mind.

Vasovagal syndrome

A disorder of the nerves supplying the blood vessels and heart that can result in dizzy episodes or blackouts. This is due to sudden drops in blood pressure because of rapid opening up (‘dilatation’) of the arteries with or without sudden slowing of the heart rate. It is usually harmless although blackouts may place the person in dangerous situations. Treatment can involve tablets and/or a pacemaker. It can be diagnosed with a tilt-test or implantable loop recorder (see pages XX).


The two bottom chambers of the heart that pump blood to the body and the lungs.


From, or belonging to, the ventricle.

Ventricular fibrillation

In ventricular fibrillation (VF) the muscle fibres in the ventricles contract completely randomly so the ventricles cannot perform their pumping action.

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