Long QT Syndrome
What is Long QT syndrome?
Long QT syndrome (LQTS) is a cardiac syndrome. LQTS is an indication of rapid and chaotic heart beat and triggering factor of sudden fainting, or blackout and even convulsion attacks.
Long QT syndrome is detected when abnormal findings obtained from electrocardiogram (ECG) recording. ECG records the cardiac impulse generation and transmission throughout the special cardiac neuronal system contains SA node, AV node, purkinje fibers and bundle of his.
There are five graphical presentation present in ECG, which include P, Q, R, S, T. QT interval represents ventricular impulse transmission. QT is the time required to ventricles for contracting and then regain the charge. Prolongation of QT often recorded in healthy person after extensive physical activities, or emotional excitement or during anxiety.
Long QT syndrome is congenital disorders and cause by genetic disorder. Some inherited Long QT syndrome is associated with congenital hearing impairment.
Sign & symptoms
There is usually no external physical sign observed. Long QT Syndrome is asymptomatic for some individuals.
The clinical presentation of the Long QT syndrome includes:
- Sudden unconsciousness due to interrupted heart rhythm
- Unexplained convulsive attack
- Uncontrolled abnormal rate and rhythm of the heartbeat, that arrhythmic attack is medically termed as “torsade de pointes”.
Brain need maximum energy to work accordingly. This energy is supplied through blood. In LQTS, the uncontrolled contraction and relaxation within the ventricle causes improper blood circulation. Brain gets inadequate oxygen supply and starvation of oxygen in the brain tissue causes sudden unconsciousness.
Some risk factors triggering the condition, such as stress, extensive physical exercise, a hasty noise and shallow hear rate during sleep. But sometime, Long QT syndrome arises without interference of triggering factors.
The unexpected persistent abnormal heart rhythms can cause rapid, uncoordinated series of contractions. This condition is called as ventricular fibrillation. This condition needs immediate medical attention to avoid cessation of cardiac activity, that leads to sudden death.
Causes
There are two possible reasons for the development of the long term QT syndrome, that is Acquired LQTS and Congenital LQTS.
Acquired LQTS
Certain medications can influence to prolongation of QT intervals. The development of the sensitivity towards certain medications may be associated with genetic reasons. The identified different medications, which can cause LQTS are
- Certain antidepressant and antipsychotic medications
- Some antihistamines
- Certain antibiotics
- Cholesterol-lowering medications
- Certain diabetes medications
- Diuretics
- Antiarrhythmic medications
Congenital LQTS
The inherited autosomal Long QT syndrome is developed due to abnormal genetic alteration affects the ion channels. The affected ion channels cause prolonging the the recovery phase after contraction of the ventricles. Approximately 17 genes have direct correlation with long QT syndrome.
The possible abnormality in mutation can develop by 100 different ways. Medical experts classified Congenital LQTS into the following two types:
Romano-Ward syndrome
This is the usual type of congenital LQTS. In this type, only one parent carry single abnormal genetic variation. There is a negligible chance of development of the hearing impairment.
Jervell and Lange-Nielsen syndrome
This type of LQTS is rare, but more severe than in Romano-Ward syndrome. In this condition, both parents contributed to transmitting abnormal gene and usually act as carriers. In this case, children also suffer from hearing impairment in addition with long QT syndrome.
Diagnosis
The following diagnostic tests are usually conducted for diagnosis and classify the type of Long QT Syndrome:
ECG: The recording of the electric impulse and graphical representation is conducted.
Holter monitoring: This is a 24 hour ECG recording system to monitor the pattern of electrical impulse activity throughout the day.
Event monitoring: The ECG pattern is recorded for prolonged periods may be for a few weeks or months. The device is attached to the body. When symptoms arise pressing of device button can record the pattern of heart rhythm and doctors can monitor the altered condition.
A nonexercise (medication) stress test: In this test certain medication like Adrenalin is administered in the patient’s body to estimates the responsible gene involvement. Adrenalin stimulates heart similar as exercise.
Genetic test: Genetic testing helps to identify the family involvement of transmitting abnormal genetic mutation, that is responsible for the condition.
Treatment
Medication, surgery and attainment of the healthier lifestyle are the possible ways to treat the LQTS.
Medication
The most commonly prescribed drug is beta blockers. The mechanism of this drug is to minimize the sympathetic nerve impulse transmission by block the effect of adrenaline (stress hormone) to control the fast abnormal heartbeat.
Surgery
The surgical intervention is required to correct the defective nerve impulse generation system. This can be possible by surgical intervention of implantable cardioverter defibrillator (ICD).
Lifestyle
Few restrictions on the living pattern such as sports activities like swimming, which trigger sudden fainting or other serious consequences. The detail discussion with doctors and attain of certain healthy lifestyle helps to make patient more active life.
References
- Ali A Sovari; Long QT Syndrome; http://emedicine.medscape.com/article/157826-overview
- Long QT syndrome (2015); Mayo Clinic; http://www.mayoclinic.org/diseases-conditions/long-qt-syndrome/basics/definition/con-20025388
- Long QT syndrome; NHS Choices; http://www.nhs.uk/Conditions/long-QT-syndrome/Pages/Introduction.aspx
- Long Q-T Syndrome (2011); Heart & Stroke Foundation; http://www.heartandstroke.com/site/c.ikIQLcMWJtE/b.3484075/k.F8EF/Heart_disease__What_is_Long_QT_Syndrome.htm
- Long Q-T Syndrome (LQTS); Cleveland Clinic; http://my.clevelandclinic.org/services/heart/disorders/arrhythmia/long-qt-syndrome
