A 10-Year-Old Boy With Fainting Spells and Seizure Activity

Shatha M. Khatib, MD

Disclosures

September 25, 2019

The guidelines published by the American College of Cardiology, the American Heart Association, and the European Society of Cardiology consider "lifestyle modifications," defined as the contraindication of competitive sports and of all drugs known to prolong the QT interval, as a class I recommendation and an important strategy for the prevention of fatal arrhythmia in patients with congenital LQTS.[11] The mainstay of medical treatment for LQTS is the use of beta-blockers.[12] Beta-blockers shorten the QT interval, which decreases the risk for torsade de pointes arrhythmia and reduces the incidence of syncope and sudden cardiac death. They are effective in approximately 70% of patients.

In high-risk patients, implantable cardioverter-defibrillators (ICDs) appear to be the most effective therapy. An ICD may also be considered as a primary therapy if the patient has a strong family history of sudden cardiac death.[13]

Another therapeutic measure reserved for patients who continue to have symptoms despite medical therapy and ICD placement is left cervicothoracic sympathectomy (LCTS). LCTS causes sympathetic denervation of the heart and, in some cases, decreases the event rate.[13]

Because of the appreciable risk for torsades de pointes arrhythmia and sudden cardiac death without treatment, all symptomatic patients with congenital LQTS should be treated. Treating asymptomatic patients is more controversial; however, because sudden cardiac death can be the first manifestation of LQTS, a safe approach would be to treat even asymptomatic patients with at least medical therapy.[1] Patients who survive a cardiac arrest, those in whom beta-blocker therapy fails, and those with high-risk features based on family history or genetic screening should be considered for an ICD. Any workup for LQTS should be performed in consultation with a cardiologist.

Gene-specific therapy is currently an area under investigation, and the management of LQTS is increasingly being guided by gene-specific diagnoses. General recommendations based on knowledge of the patient's genotype that assist in making treatment selections include avoidance of strenuous exercise, stress, and unsupervised swimming or diving in patients with LQT1, because these are common triggers of arrhythmia. Beta-blockers are highly protective in these patients. LQT2 is also induced by exercise, but to a lesser degree than LQT1 is.

Among patients with LQT3, events are less commonly induced by exercise; they usually occur during sleep or rest. Beta-blockers are less beneficial in these patients.[3,14] In numerous case reports, mexiletine (a sodium-channel blocker) has been demonstrated to shorten the QT interval in the subgroup of patients with LQT3.

In this case, the diagnosis was confirmed by an exertional ECG recording that reproduced torsade de pointes arrhythmia. The patient was started on a beta-blocker and has since remained asymptomatic. Because of the high risk-profile in this family, his younger brother was also started on beta-blocker therapy.

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