Cardiac Diseases Long QT Syndrome
What is the Long QT Syndrome?
The Long QT Syndrome is a rare disorder of the heart's electrical system that can affect otherwise healthy people.
Although the heart's mechanical function is normal, there are defects in ion channels, which are cell structures in the heart muscle.
These electrical defects can cause a very fast heart rhythm (arrhythmia) called torsade de pointes.
This abnormal rhythm (a form of ventricular tachycardia) is too fast for the heart to beat effectively, and so the blood flow to the brain falls dramatically, causing sudden loss of consciousness, or syncope (fainting).
Why is it called Long QT Syndrome?
The name Long QT Syndrome comes from the measurement of the heart's contractions by electrocardiogram (EKG or ECG).
When the heart contracts, it emits an electrical signal that can be recorded on the ECG.
This signal produces a waveform, and different parts of this waveform are designated by lettersP,Q, R, S and T. The Q-T interval marks the time for electrical activation and inactivation of the ventricles, which are the lower chambers of the heart.
In people with the Long QT Syndrome, the Q-T interval takes longer than normal to occur.
It should be noted, however, that tests do not always reveal Long QT Syndrome.
People with the disorder do not necessarily have a prolonged Q-T interval all the time, and at the time they have an ECG, the Q-T interval may be normal.
Symptoms of the Long QT Syndrome
People with the Long QT Syndrome may have no symptoms at all.
Among those who do, fainting (syncope) and an abnormal heartbeat (arryhthmia) are common.
Symptoms occur especially during physical exercise, intense emotion (such as fright, anger, or pain), or when awakened or startled by a noise such as an alarm clock, telephone, or thunder.
Syncope is commonly misdiagnosed as a common faint, but it can be fatal. Usually, there is no warning before syncope.
What Causes the Long QT Syndrome?
The Long QT Syndrome is commonly inherited.
There are at least two inherited variants, and in one type, individuals with Long QT Syndrome are deaf.
The majority of people with Long QT Syndrome have family members with the disorder, and have had at least one episode of fainting by age 10.
Even if the disorder has not been diagnosed in the family (as relatives may have died of sudden unknown causes), any history of fainting or sudden loss of consciousness during exercise or strong emotion necessitates medical tests.
The Long QT Syndrome can also be acquired, most often through the administration of medications that are contraindicated in patients with Long QT Syndrome.
How is the Long QT Syndrome Treated?
Beta blocker medications are effective for about 90% of patients.
A small group of patients may also benefit from other drugs, either instead of or in addition to the beta blockers.
In patients who do not respond to medication, the insertion of a pacemaker or defibrillator may be effective.
Surgical cutting of certain nerves in the neck, called cervico-thoracic sympathectomy, can be effective as well.
All patients with the Long QT Syndrome should be treated, including asymptomatic patients and especially children, because sudden death often occurs with the first episode of syncope and it is not possible to predict which patients are vulnerable.
Drugs to Avoid with the Long QT Syndrome
Many drugs can prolong the Q-T interval and cause heart rhythm abnormalities. It is very important to inquire about the risk of any medication, whether it is a prescription or over-the-counter drug, that is recommended to a Long QT patient.
Some common medications that should be avoided include anesthetics and asthma medications (adrenaline), antihistamines, certain antibiotics, numerous heart medications, the gastrointestinal drug Propulsid, some antifungal drugs, psychotropic medications, the diuretic Lozol, and others.
It should also be noted that many diuretics cause potassium loss (as does extensive vomiting and diarrhea), and low potassium levels can worsen Long QT Syndrome.