Long QT Syndrome medical and device therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]

Overview

There are two tratment options in individuals with LQTS: arrhythmia prevention, and arrhythmia termination.

Withdrawal of Drugs and Supplements

Certain medications should be avoided in persons with long QT syndrome, to avoid worsening the condition. These medications include certain appetite suppressants, decongestants, and antibiotics such as erythromycin. Illicit drugs such as cocaine and amphetamines can be even more dangerous in persons with long QT syndrome.

Correct Electrolyte Disturbances

Illness that cause hypokalemia due to vomiting and diarrhea can aggravate long QT syndrome. Medications that can lower the levels of potassium in the blood should also be avoided.

Primary Prevention

Beta Blockers

Beta blockers are first line therapy in the treatment of Long QT syndrome.

Arrhythmia suppression involves the use of medications or surgical procedures that attack the underlying cause of the arrhythmias associated with LQTS. Since the cause of arrhythmias in LQTS is after depolarizations, and these after depolarizations are increased in states of adrenergic stimulation, steps can be taken to blunt adrenergic stimulation in these individuals. beta receptor blocking agents decrease the risk of stress or catecholamine induced arrhythmias.

AICD Implantation

An AICD should be implanted if:

• The QTc is > 550 ms and if it is not LQT1
• LQT2 in women and the QTc is > 500 ms, with or without symptoms
• In infants with 2:1 AV block (controversial)
• In JLNS (LQTS with deafness) given its malignant propensity (controversial)

Sympathetic Denervation

Videoscopic Left Cardiac Sympathetic Denervation Surgery is not a cure, but reduces the risk of sudden cardiac death and is indicated if:

• The patient does not tolerate beta blockers or breaks through beta blockers
• The patient faints while on beta blockers
• There is a history of VF terminating AICD shocks
• In young patients under the age of 12 where beta blockers are not deemed protective enough and where the morbidity of an AICD seems excessive.

Secondary Prevention

Patients with Long QT syndrome should undergo secondary prevention with AICD implantation if they sustain an aborted cardiac arrest orsudden cardiac death.

Arrhythmia prevention

In 2004 it has been shown that genotype and QT interval duration are independent predictors of recurrence of life-threatening events during beta-blockers therapy. Specifically the presence of QTc >500ms and LQT2 and LQT3 genotype are associated with the highest incidence of recurrence. In these patients primary prevention with ICD (Implantable Cardioverster Defibrilator) implantaion can be considered.

• Potassium supplementation. If the potassium content in the blood rises, the action potential shortens and due to this reason it is believed that increasing potassium concentration could minimize the occurrence of arrhythmias. It should work best in LQT2 since the HERG channel is especially sensible to potassium concentration, but the use is experimental and not evidence based.
• Mexiletine. A sodium channel blocker. In LQT3 the problem is that the sodium channel does not close properly. Mexiletine closes these channels and is believed to be usable when other therapies fail. It should be especially effective in LQT3 but there is no evidence based documentation.
• Amputation of the cervical sympathetic chain (left stellectomy). This may be used as an add-on therapy to beta blockers but modern therapy mostly favors ICD implantation if beta blocker therapy fails.

Arrhythmia termination

Arrhythmia termination involves stopping a life-threatening arrhythmia once it has already occurred. The only effective form of arrhythmia termination in individuals with LQTS is placement of an implantable cardioverter-defibrillator (ICD). ICD are commonly used in patients with syncopes despite beta blocker therapy, and in patients who have experienced a cardiac arrest.

With better knowledge of the genetics underlying the long QT syndrome, more precise treatments will be readily available.