The Long QT Syndrome is a disturbance of the heart's electrical system. A genetic mutation causes a defect in the heart cells, called ion channels, which then prolongs the time the heart takes to electrically recharge after each heartbeat (known as the QT interval).
LQTS is usually genetic. If one family member is found to have LQTS, all family members need to be screened. The prevalence of LQTS is approximately 1 in 5000 individuals. LQTS may be acquired due to certain medications, toxins, electrolyte disturbances, or other forms of heart disease.
Symptoms
- Fainting
- Cardiac Arrest
- Syndactaly (webbed fingers and/or toes) may also be an indication that a person has LQTS.
Long QT Syndrome is believed to be a common cause of unexplained cardiac arrest among school athletes, as well as the probable cause of many unexplained drownings.
Diagnosis
Diagnosis is made primarily upon recognition of a prolonged QTc interval on the electrocardiogram. A QTc of .47 seconds in males and .48 seconds in females appears to be diagnostic of LQTS, in the absence of certain drugs, toxins, an electrolyte disturbance, or other forms of heart disease. A computer generated QTc may not be correct and should be hand measured by a physician. Certain T-Wave abnormalities on an ECG may also be indicative of LQTS. The most effective way to determine LQTS is with an exercise ECG. A "Holter" ECG will often assist in clarifying the diagnosis.
A careful history of the events surrounding the syncopal event usually differentiates LQTS induced syncope from the common faint, known as vasovagal or neurocardiogenic syncope. The LQTS syncope is usually without warning. Suspect LQTS when there is a family history of unexplained fainting or sudden death in young people. Approximately one-half of LQTS individuals never exhibit symptoms; therefore, the lack of prior symptoms does not exclude a person or a family from having LQTS.
Treatment
- Beta-blocker medications (usually effective in about 90% of LQTS individuals).
- Pacemaker or an implantable cardioverter defibrillator (ICD) may be necessary if medications are not effective.
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