Heart & Stroke Conditions Explained


Long QT syndrome

LQTS is an inherited condition. It is a disturbance of the heart’s electrical system which causes heart rhythm problems.

It is estimated that 1 person in every 5,000 has LQTS. The condition is generally inherited; however it can also be caused by certain medications you may be taking for other medical conditions.

Each child of a person with LQTS has a 50% chance of having the condition. If you have LQTS, your mother or father will also have the condition.


There are two main types of LQTS:


  • The more common Romano-Ward syndrome, which is inherited from one parent.
  • The Jervell, Lange-Nielsen form of LQTS. This is rare, as both parents must have the abnormal gene to pass on the condition. This type of LQTS has a link with deafness.


LQTS usually affects the potassium channels in your heart muscle cells and this causes a delay in the flow of potassium ions out of your heart muscle cells.

In a small number of people with LQTS, the sodium channels are affected and too many sodium ions are allowed into the cells. The movement of potassium and sodium is essential for the normal electrical activity responsible for your heart beat. Which is why LQTS can lead to heart rhythm problems.


Related topics: palpitations, electrocardiogram (ECG), Long QT Syndrome Support Group, SADS, implantable defibrillator (ICD).


Long QT syndrome

A person with LQTS is prone to fainting spells/blackouts, dizziness, palpitations and even sudden cardiac death.

These symptoms are caused by a very fast heart rhythm called Torsade de Pointes. Symptoms happen suddenly and often without warning. The risk of sudden death is greater if you have had a previous cardiac arrest, blackouts, a very long QT interval on your ECG or have sodium channel mutations.


Fainting, blackouts and family history

Fainting spells/blackout are the most common symptom of LQTS. But there are many other reasons for a fainting spell. With LQTS, it is very important to look at family history. LQTS symptoms generally present in young people (under 40 years) and thus a family history of sudden, unexplained death of young people or family members with a history of unexplained fainting spells/blackouts is a very important consideration.


Common faint or LQTS?

A regular or common faint usually gives warning signs such as blurred vision or sweating just before the faint occurs. However, a blackout or faint due to LQTS is usually sudden and without warning. It often happens during or shortly after some form of physical and emotional exertion. This could be during exercise or upon hearing very good or very bad news. Sudden noises such as alarm clocks and doorbells can also act as triggers.


Other symptoms and the importance of family history

Other symptoms of LQTS include dizziness and palpitations. Unfortunately sometimes the first symptom of LQTS is cardiac arrest (when the heart stops beating) and sudden cardiac death.

Up to 50% of people with Long QT Syndrome never have any symptoms. Therefore is it very important if you have LQTS that your close family members are regularly checked for the condition, even if they have no symptoms, as sudden cardiac death might be the first symptom.


Long QT syndrome

LQTS is generally an inherited condition. Each child of a person with LQTS has a 50% chance of having the condition.

Sometimes the gene carrying LQTS can be identified in a family, in which case identifying members with LQTS becomes much easier.

Certain medications and medical conditions can also cause Long QT syndrome. This is a rare, acquired form of LQTS. It is brought on by some prescribed medicines and illegal drugs.

However, it is not known whether or not people affected by acquired LQTS already have a genetic pre-disposition towards the condition.


Long QT syndrome

If you have LQTS it is important that you take your medication and follow your cardiologist’s instructions.

It is also very important to have family members regularly checked for LQTS by a doctor, even if they don’t have any symptoms.

All first-degree relatives of the person with LQTS should be tested for the condition. A first-degree relative is a mother, father, brother, sister, son or daughter.

It is very important that the parents and grand-parents of the affected person are tested so that other relatives at risk can be identified.

Relatives should be tested at regular intervals on the advice of their doctors.


Long QT syndrome

The name comes from a measurement on an electrocardiogram (ECG) called the QT-Interval.

When a person with LQTS has an ECG test, the QT-Interval recorded on the ECG is prolonged. A small percentage of people with LQTS will have a normal ECG.

LQTS is generally diagnosed by electrocardiogram (ECG). The machine records your heart’s electrical activity, which can show a prolonged QT-Interval. An exercise stress test may also be used.

This measures your heart’s electrical activity while you are exercising. Or a Holter monitor may be used to record your heart’s rate and rhythm over 24 hours to pick up intermittent heart rhythm disturbances that may be missed by an ECG.

Sometimes the gene carrying LQTS can be identified in a family, in which case identifying members with LQTS becomes much easier.


Long QT syndrome

All patients should be treated whether they have symptoms or not.

This is because sudden death may be the first symptom a person with LQTS experiences. It is not possible to identify the patients who will and will not develop serious symptoms of LQTS. Therefore all patients should receive preventative treatment.



The most common medication is Beta Blockers. These medicines stop the action of hormones such as adrenaline that make the heart beat faster. For most people with LQTS, medication is the only treatment required.

Some people may need devices such as pacemakers or ICDs fitted to help control dangerous heart rhythms.


Accepting LQTS

Accepting the diagnosis of a medical problem is never easy. Some people find it more difficult than others. As many people diagnosed with LQTS are children or young people, coming to terms with LQTS is even more difficult on top of all the other psychological challenges of growing up.



People with LQTS should avoid competitive sports and activities that place high physical demands on the body. Physical activities such as walking, moderate hiking and biking, and golf are suitable. However you should check with your medical professionals about your individual case.

If you have LQTS, it is also important to get advice on exercise in relation to your children, even if they have no symptoms. After treatment, it may be possible to resume certain sports, in consultation with your doctor.


Foods and drinks

There are some foods that can inhibit the effectiveness of the medication you are taking for LQTS. Please check with your doctor and read the information sheet provided with your tablets for information on foods that might interfere with your medicine.

There are also some foods and drinks that can increase your heart rate, such as caffeine, and act as a trigger for symptoms of LQTS. Caffeine is found in tea, coffee, fizzy drinks, high-energy drinks and in many over-the-counter cold & flu remedies and pain medicines.

Make sure to read the list of ingredients on foods, drinks and medicines.



Some medicines can prolong the QT-Interval and should not be taken by people with LQTS. You can get a full list of these drugs from web sites such as www.qtdrugs.org As new drugs are always becoming available, you need to check the list regularly.

Make sure that your doctors and dentists are fully aware of your condition and that they know there are many medicines that are dangerous for you to take. Always ask your doctor before taking any new prescription or non-prescription medicine.

Support for You

Long QT syndrome

The Irish Heart Foundation offers a range of free support services to those affected by heart disease or stroke that can greatly improve their quality of life. These include support groups, physical exercise classes, therapy sessions and more.

For more information on these supports, see our Patient Supports page.

If you have any questions about heart disease or stroke, you can also call the Irish Heart Foundation’s Nurse Support on (01) 668 5001 to speak to a nurse specialist who will answer your questions, and give you guidance and reassurance.


Long QT Syndrome Ireland Facebook Group

The Long QT Syndrome Ireland Facebook group is independently facilitated by a group of people living with LQTS – join now. 


Long QT syndrome

Read our resources for further information:

Long QT Syndrome Support Group

This support group is a voluntary group set up in association with the Irish Heart Foundation to provide information and support to people with LQTS and their families.

The support group wishes to create more awareness of the condition so that patients fully understand the implications of LQTS on themselves and their families.

The support group wants to emphasise the importance of looking after other family members; as they know so many families who have lost many young people through: a lack of awareness of the hereditary nature of LQTS; and a lack of understanding of the need to continuously monitor the children of people with LQTS even when there are no obvious symptoms.

See the booklet for more information.

Implantable Cardioverter Defibrillator (ICD) Support Group

All of these support groups are also affiliated or connected to the Irish Heart Foundation. For more information, simply freephone us on 1800 25 25 50  or click on the Support Group the links above.

For added information on LQTS and related drugs visit www.qtdrugs.org

Translate »