A condition where calcium enters the heart muscles longer or more than it should leading to changes in heart function and heart beat, it can also occur if one has low potassium in the blood leading to changes in heart function.
Those at risk include:
Children who are deaf at birth
Children and young adults who have unexplained sudden death or syncope in family members
Blood relatives of family members with LQTS
Those with LQTS taking medications that can further prolong the QT intervals
There are many types of Long QT syndromes:
Multiple ion channel abnormalities have been discovered. The most common ones include LQT1, LQT2, LQT3, LQT4, LQT5; these are classified by the type of channel which causes the LQTS. The type of LQTS classification is related to the risk of future cardiac events, those with LQT3 having the highest risk of life-threatening arrhythmias.
Both parents are carriers of the abnormal gene, but they may not manifest LQTS. Each child has a 25-percent chance of inheriting LQTS. This syndrome is associated with deafness at birth and is extremely rare, as there is a small chance that both parents would carry the LQTS gene.
One parent has LQTS and the other parent usually does not. Each child has a 50-percent chance of inheriting the abnormal gene. In this syndrome, hearing is normal; however the likelihood that children in this family would have LQTS is greater. The gene may be present in all the couple’s children, some of them or none at all.
Referred to as long QT syndrome type 8 (LQT8), is a rare multisystemic genetic disorder affecting the heart and several other organs, including the skeleton, metabolic system and the brain.
QT prolongation is when the heart muscle takes longer than normal to recharge between beats.
It is an electrical disturbance which can be seen on an electrocardiogram (ECG).
The QT interval is the electrocardiographic parameter representing the time required for the heart to complete a cycle of contraction and relaxation
In Timothy syndrome – the calcium channels of the body stay open longer than they should, allowing calcium to overload cells. When this occurs in the heart, the normal rhythm is disrupted, leading to arrhythmia and long QT syndrome.
When the QT interval is exceptionally prolonged, as is the case in patients with Timothy syndrome, a slowing in the conduction of the electrical impulses from the atria (top part of heart-chamber) to the ventricles (bottom part of heart- chamber) can occur.
This phenomenon is called “atrioventricular block” and can result in a severe reduction of the heart rate (bradycardia).
This condition belongs to a heterogeneous group of diseases collectively classified as “long QT syndrome” or LQTS.
Long QT syndrome affects males and females in equal numbers and has been identified in all ethnic groups. The exact incidence and prevalence of the disorder is not known.
Always tell your Medical Healthcare Professional that you have long QT syndrome. Any new medicine, whether on a prescription (POM) or over the counter (OTC), will need to be carefully checked to see if it’s suitable for you
Talk to your pharmacist when purchasing Over The Counter (OTC) medication particularly:
Diphenhydramine and other anti histamines (anti – histamine mainly for sleep, but are also found in drowsy cold and flu medications)
Terfenadine (antihistamine)
Fluconazole (used in fungal conditions including thrush)
Cause
Long QT syndrome has been shown to be caused by mutations in one of at least 15 different ion-channel genes: the KCNQ1 gene causing LQTS1; KCNH2 causing LQT2; SCN5A causing LQT3; ANK2 causing LQTS4; KCNE1 causing LQTS5; KCNE2 causing LQT6; KCNJ2 causing LQTS7; CACNA1c causing LQTS8; CAV3 causing LQTS9; SCN4B causing LQTS10; AKAB9 causing LQTS11; SNTA1 causing LQTS12; KCNJ5 causing LQTS13; CALM1 causing LQTS14; and CALM2 causing LQTS15.
Mutations in KCNQ1, KCNH2, and SCN5A correlate to Long QT types 1-3 and account for the majority (60-75%) of genetically identifiable cases.
Timothy syndrome is due to changes (mutations) in the CACNA1C gene[3] that provides the instructions for the assembly of special proteins known as “calcium channels.” and CACNA1C has long been known to play a role in the development and survival of nerve cells, hence one may have neuroglocial (nerve) disorders as well.
These channels are located on the external membrane of cells and allow calcium ions to flow into the cardiac cells (It Provides the body with instructions for how to create channels to deliver calcium to cells. Calcium is involved in numerous physiological functions, including heart contractions and cell-to-cell communication (including those in the brain and spinal cord).
Calcium channels are present not only in the heart but in many other organs, the clinical manifestations of the disease are multisystemic.
In Timothy syndrome – the calcium channels of the body stay open longer than they should, allowing calcium to overload cells. When this occurs in the heart, the normal rhythm is disrupted, leading to arrhythmia and long QT syndrome.
This means that only a single copy of an abnormal gene is sufficient to cause the disease to be inherited (meaning it takes only one copy of a mutated CACNA1C gene from one parent for a child to develop the disorder).
The abnormal gene can be inherited from either parent or it can be the result of a new mutation in the affected individual.
Most cases are the result of a new gene mutation since there is no evidence of TS being passed through families.
Why a spontaneous CACNA1C mutation occurs in a parent is unknown.
Less often, Timothy syndrome can occur as a result of genetic mosaicism.
Mosaicism means that the parent has the mutation in some cells of their body (like the egg or sperm) but not others.
Mosaicism is associated with less severe symptoms of Timothy syndrome compared to those who inherit the mutation in an autosomal dominant pattern
Verywell health
Other:
Reduced levels of potassium in the blood or it may be caused by the intake of drugs that block potassium channels.
Long QT Syndrome Type 2 (LQT2) results from reduced potassium current flowing through the hERG channel encoded by the KCNH2 gene. Emotional stress, surprise, and startling can initiate arrhythmias in people with LQT2
Stress
A sudden noise – such as an alarm
Strenuous exercise (or within a few minutes after)- particularly swimming
Type 3 long–QT syndrome (LQT3) is caused by gain-of-function mutations in the SCN5A-encoded Nav1. 5 sodium channel involving a pathological increase in late sodium current, a pathological increase in the window current (as one of the mechanisms of the late sodium inward current), or both
Source: www.revespcardiol.org 'Penetrance measures the proportion of individuals in a population who carry a specific gene and express the related trait'
Symptoms
Rapid heart beat?
Altered heart rhythm (slow beating of heart)?
Thickening of the cardiac walls (cardiac hypertrophy), Short of breath and/or breathing difficulties (whether after exercise or not) and/or wheezing?
Balance and dizziness , blackouts orfainting, because the heart has stopped pumping blood properly and the brain is temporarily starved of oxygen – the heart’s rhythm returns to normal within a few minutes and the person regains consciousness?
heart palpitations, when the heart is beating in a fast or unpredictable way?
Seizures, which sometimes happen instead of a blackout when the brain is starved of oxygen?
Difficult to concentrate /difficulty in concentrating/memory problems and/or learning difficulties?
Low set ears and/or Webbed fingers or toes that are fused together and may involve both the hands and the feet?
Baldness at birth?
Facial changes?
Low-set ears?
A lower nasal bridge?
Thin upper lip?
Small upper jaw?
Small, widely spaced teeth with a increased chance of cavities?
Bone and joint movement problems and/or difficulty using arms and/or body and/or legs and/or lack of stamina and/or walking difficulties and/or crawling difficulties and/or rolling over difficulties?
Complications /Information to beware of/General tips:
With the right treatment, it’s possible to avoid long QT syndrome having a major impact on your day-to-day life. However, you may need to make some lifestyle adjustments to reduce your risk of having blackouts i.e.
You may not be able to exercise strenuously or play competitive sports, and may need to try to avoid startling noises, such as alarm clocks.
Avoiding stressful situations may also be recommended.
Rehydrating properly after a tummy upset is also essential, usually with supplements containing salt and sugar.
Your doctor may prescribe potassium supplements or suggest increasing the amount of potassium-rich foods in your diet. Good sources of potassium include:
Bananas
Vegetables
Pulses
Nuts and seeds
Milk
Fish
Shellfish
Beef
Chicken
Turkey
Bread
Always tell your Medical Healthcare Professional that you have long QT syndrome. Any new medicine, whether on a prescription (POM) or over the counter (OTC), will need to be carefully checked to see if it’s suitable for you
Rare inherited heart disorder characterised by abnormalities of the heart’s electrical system.
The symptoms vary greatly from case to case.
Some affected individuals will experience no apparent symptoms (asymptomatic); others may develop irregular heartbeats leading to episodes of unconsciousness (syncope), cardiac arrest, and, potentially, sudden death often during sleep.
An inherited as an autosomal dominant trait and is caused by mutations in the SCN5A gene, the same gene that causes LQTS3 (allelic disorders).
These conditions are very difficult to diagnose, a specialist opinion is required.
OMIM is intended for use primarily by physicians and other professionals concerned with genetic disorders, by genetics researchers, and by advanced students in science and medicine. While the OMIM database is open to the public, users seeking information about a personal medical or genetic condition are urged to consult with a qualified physician for diagnosis and for answers to personal questions.
Detailed Information
Please copy and paste any key words from the title: Long QT syndrome in the following respective 'Medtick References and/or Sources' to find out more about the disease (this also may include diagnosis tests and generic medical treatments).
The Pharmaceutical Journal covers analysis, features, opinion, learning and careers articles, providing insight and knowledge about drugs, pharmacy practice, medicines use and healthcare policy in the context of the pharmacy profession and pharmaceutical science.
